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X11VNC(1)                        User Commands                       X11VNC(1)

NAME
       x11vnc - allow VNC connections to real X11 displays
                version: 0.9.16, lastmod: 2019-01-05

SYNOPSIS
       x11vnc [OPTION]...

DESCRIPTION
       Typical usage is:

              Run  this  command  in  a shell on the remote machine "far-host"
              with X session you wish to view:

              x11vnc -display :0

              Then run this in another window on the machine you  are  sitting
              at:

              vncviewer far-host:0

       Once x11vnc establishes connections with the X11 server and starts lis-
       tening as a VNC server it will print out a string: PORT=XXXX where XXXX
       is  typically  5900  (the default VNC server port).  One would next run
       something like this on the local machine: "vncviewer hostname:N"  where
       "hostname"  is  the  name of the machine running x11vnc and N is XXXX -
       5900, i.e. usually "vncviewer hostname:0".

       By default x11vnc will not allow the screen to be shared  and  it  will
       exit as soon as the client disconnects.  See -shared and -forever below
       to override these protections.  See the FAQ for details how  to  tunnel
       the  VNC  connection  through  an encrypted channel such as ssh(1).  In
       brief:

              ssh -t -L 5900:localhost:5900 far-host 'x11vnc -localhost  -dis-
              play :0'

       % vncviewer -encodings 'copyrect tight zrle hextile' localhost:0

       Also,  use of a VNC password (-rfbauth or -passwdfile) is strongly rec-
       ommended.

       For   additional   info   see:   http://www.karlrunge.com/x11vnc/   and
       http://www.karlrunge.com/x11vnc/faq.html

       Config  file support: if the file $HOME/.x11vncrc exists then each line
       in it is treated as a single command line option.  Disable with  -norc.
       For  each option name, the leading character "-" is not required.  E.g.
       a line that is either "forever" or  "-forever"  may  be  used  and  are
       equivalent.   Likewise  "wait  100"  or  "-wait 100" are acceptable and
       equivalent lines.  The "#" character comments out to  the  end  of  the
       line in the usual way (backslash it for a literal).  Leading and trail-
       ing whitespace is trimmed off.  Lines may be continued with  a  "\"  as
       the last character of a line (it becomes a space character).

OPTIONS
       -display disp

              X11  server  display  to  connect  to, usually :0.  The X server
              process must be running on same  machine  and  support  MIT-SHM.
              Equivalent to setting the DISPLAY environment variable to disp.

              See  the  description  below  of the "-display WAIT:..."  exten-
              sions, where alias "-find" will find the user's display automat-
              ically,  and  "-create" will create a Xvfb session if no session
              is found.

       -auth file

              Set the X authority file to be file, equivalent to  setting  the
              XAUTHORITY environment variable to file before startup.  Same as
              -xauth file.  See Xsecurity(7) , xauth(1)  man  pages  for  more
              info.

              Use  '-auth  guess'  to  have x11vnc use its -findauth mechanism
              (described below) to try to guess the  XAUTHORITY  filename  and
              use it.

              XDM/GDM/KDM:  if you are running x11vnc as root and want to find
              the XAUTHORITY before anyone has logged into an X  session  yet,
              use:  x11vnc -env FD_XDM=1 -auth guess ...  (This will also find
              the XAUTHORITY if a user is already logged into the X  session.)
              When  running  as  root,  FD_XDM=1  will be tried if the initial
              -auth guess fails.

       -N

              If the X display is :N, try to set the VNC display to also be :N
              This  just  sets  the -rfbport option to 5900+N The program will
              exit immediately if that port is not available.  The  -N  option
              only  works with normal -display usage, e.g. :0 or :8, -N is ig-
              nored in the -display WAIT:..., -create, -find, -svc, -redirect,
              etc modes.

       -autoport n

              Automatically  probe for a free VNC port starting at n.  The de-
              fault is to start probing at 5900.  Use this to stay  away  from
              other VNC servers near 5900.

       -rfbport str

              The  VNC  port to listen on (a LibVNCServer option), e.g.  5900,
              5901, etc.  If specified as "-rfbport PROMPT"  then  the  x11vnc
              -gui is used to prompt the user to enter the port number.

       -6

              IPv6  listening  support.  In addition to IPv4, the IPv6 address
              is listened on for incoming connections.  The same  port  number
              as IPv4 is used.

              NOTE:   This  x11vnc  binary  was compiled to have the "-6" IPv6
              listening mode ENABLED by default (CPPFLAGS -DX11VNC_LISTEN6=1).
              So to disable IPv6 listening mode you MUST supply the "-no6" op-
              tion (see below.)

              The "-6" mode works for both normal  connections  and  -ssl  en-
              crypted ones.  Nearly everything is supported for the IPv6 case,
              but there are a few exceptions.  See -stunnel for its IPv6  sup-
              port.

              Currently,  for  absolutely everything to work correctly the ma-
              chine may need to have some IPv4 support, at the least  for  the
              loopback interface.  However, for nearly all usage modes no IPv4
              support is required. See -noipv4.

              If you have trouble compiling  or  running  in  IPv6  mode,  set
              -DX11VNC_IPV6=0  in  CPPFLAGS  when  configuring to disable IPv6
              support.

       -no6

              Disable IPv6 listening support (only useful if the "-6" mode  is
              compiled  in  to be the default; see the X11VNC_LISTEN6 descrip-
              tion above under "-6".)

       -noipv6

              Do not try to use IPv6 for any listening or connecting  sockets.
              This  includes  both  the listening service port(s) and outgoing
              connections from -connect,  -connect_or_exit,  or  -proxy.   Use
              this if you are having problems due to IPv6.

       -noipv4

              Do  not try to use IPv4 for any listening or connecting sockets.
              This is mainly for  exploring  the  behavior  of  x11vnc  on  an
              IPv6-only system, but may have other uses.

       -reopen

              If  the X server connection is disconnected, try to reopen the X
              display (up to one time.)  This is of use for  display  managers
              like  GDM  (KillInitClients  option) that kill x11vnc just after
              the user logs into the X session.  Note: the reopened state  may
              be  unstable.  Set X11VNC_REOPEN_DISPLAY=n to reopen n times and
              set X11VNC_REOPEN_SLEEP_MAX to the number  of  seconds,  default
              10, to keep trying to reopen the display (once per second.)

              Update:  as  of 0.9.9, x11vnc tries to automatically avoid being
              killed by the display manager by delaying  creating  windows  or
              using   XFIXES.    So   you  shouldn't  need  to  use  KillInit-
              Clients=false as long as you log in quickly  enough  (within  45
              seconds  of  connecting.)   You  can  disable  this  by  setting
              X11VNC_AVOID_WINDOWS=never.  You can also set it to  the  number
              of seconds to delay.

       -reflect host:N

              Instead  of  connecting  to and polling an X display, connect to
              the remote VNC server host:N and be a reflector/repeater for it.
              This  is useful for trying to manage the case of many simultane-
              ous VNC viewers (e.g. classroom broadcasting)  where,  e.g.  you
              put  a  repeater on each network switch, etc, to improve perfor-
              mance by distributing the load  and  network  traffic.   Implies
              -shared  (use  -noshared  as a later option to disable). See the
              discussion below under -rawfb vnc:host:N for more details.

       -id windowid

              Show the X window corresponding to windowid not the entire  dis-
              play.   New  windows like popup menus, transient toplevels, etc,
              may not be seen or may  be  clipped.   Disabling  SaveUnders  or
              BackingStore  in  the  X  server may help show them.  x11vnc may
              crash if the window is  initially  partially  obscured,  changes
              size, is iconified, etc.  Some steps are taken to avoid this and
              the -xrandr mechanism is used to track resizes.  Use xwininfo(1)
              to get the window id, or use "-id pick" to have x11vnc run xwin-
              info(1) for you and extract the id.  The -id  option  is  useful
              for exporting very simple applications (e.g. the current view on
              a webcam).

       -sid windowid

              As -id, but instead of using the window  directly  it  shifts  a
              root view to it: this shows SaveUnders menus, etc, although they
              will be clipped if they extend beyond the window.

       -appshare

              Simple application sharing based on the -id/-sid mechanism.  Ev-
              ery  new  toplevel window that the application creates induces a
              new viewer window via a reverse connection.   The  -id/-sid  and
              -connect options are required.  Run 'x11vnc -appshare -help' for
              more info.

       -clip WxH+X+Y

              Only show the sub-region of the full display that corresponds to
              the  rectangle  geometry with size WxH and offset +X+Y.  The VNC
              display has size WxH (i.e. smaller than the full display).  This
              also works for -id/-sid mode where the offset is relative to the
              upper left corner of the selected window.   An  example  use  of
              this  option  would  be to split a large (e.g. Xinerama) display
              into two parts to be accessed via separate viewers by running  a
              separate x11vnc on each part.

              Use  '-clip  xinerama0' to clip to the first xinerama sub-screen
              (if xinerama is active).  xinerama1 for the 2nd sub-screen, etc.
              This way you don't need to figure out the WxH+X+Y of the desired
              xinerama sub-screen.  screens are sorted in increasing  distance
              from the (0,0) origin (I.e. not the Xserver's order).

       -flashcmap

              In  8bpp  indexed color, let the installed colormap flash as the
              pointer moves from window to window (slow).  Also try the -8to24
              option to avoid flash altogether.

       -shiftcmap n

              Rare  problem,  but  some 8bpp displays use less than 256 color-
              cells (e.g. 16-color grayscale, perhaps the other bits are  used
              for double buffering) *and* also need to shift the pixels values
              away from 0, .., ncells.  n indicates the shift to be applied to
              the  pixel  values.  To see the pixel values set DEBUG_CMAP=1 to
              print out a colormap histogram.  Example: -shiftcmap 240

       -notruecolor

              For 8bpp displays, force indexed color (i.e. a colormap) even if
              it looks like 8bpp TrueColor (rare problem).

       -advertise_truecolor

              If  the  X11  display is indexed color, lie to clients when they
              first connect by telling them it is  truecolor.   To  workaround
              RealVNC:  inPF  has colourMap but not 8bpp Use '-advertise_true-
              color reset' to reset client fb too.

       -visual n

              This option probably does not do  what  you  think.   It  simply
              *forces*  the visual used for the framebuffer; this may be a bad
              thing... (e.g. messes up colors or cause a crash). It is  useful
              for  testing  and for some workarounds.  n may be a decimal num-
              ber, or 0x hex.  Run xdpyinfo(1) for the values.  One  may  also
              use  "TrueColor",  etc. see <X11/X.h> for a list.  If the string
              ends in ":m" then for better or for worse the  visual  depth  is
              forced  to be m.  You may want to use -noshm when using this op-
              tion (so XGetImage may automatically translate the pixel data).

       -overlay

              Handle multiple depth visuals on one screen, e.g. 8+24 and  24+8
              overlay  visuals  (the  32  bits per pixel are packed with 8 for
              PseudoColor and 24 for TrueColor).

              Currently -overlay only works on Solaris  via  XReadScreen(3X11)
              and  IRIX  using XReadDisplay(3).  On Solaris there is a problem
              with image "bleeding" around transient popup menus (but not  for
              the menu itself): a workaround is to disable SaveUnders by pass-
              ing the "-su" argument to Xsun (in /etc/dt/config/Xservers).

              Use -overlay as a workaround for  situations  like  these:  Some
              legacy  applications  require  the  default  visual  to  be 8bpp
              (8+24), or they will use 8bpp PseudoColor even when the  default
              visual  is  depth 24 TrueColor (24+8).  In these cases colors in
              some windows will be incorrect  in  x11vnc  unless  -overlay  is
              used.   Another  use  of -overlay is to enable showing the exact
              mouse cursor shape (details below).

              Under -overlay, performance will be somewhat slower due  to  the
              extra  image  transformations required.  For optimal performance
              do not use -overlay, but rather configure the X server  so  that
              the  default  visual  is  depth 24 TrueColor and try to have all
              apps use that visual (e.g. some apps have -use24 or -visual  op-
              tions).

       -overlay_nocursor

              Sets  -overlay,  but does not try to draw the exact mouse cursor
              shape using the overlay mechanism.

       -8to24 [opts]

              Try this option if -overlay is not supported on your OS, and you
              have  a  legacy  8bpp app that you want to view on a multi-depth
              display with default depth 24 (and is 32 bpp) OR have a  default
              depth  8  display  with  depth 24 overlay windows for some apps.
              This option may not work on all X servers and  hardware  (tested
              on  XFree86/Xorg mga driver and Xsun).  The "opts" string is not
              required and is described below.

              This mode enables a hack where x11vnc monitors windows within  3
              levels  from  the root window.  If it finds any that are 8bpp it
              extracts the indexed color pixel values  using  XGetImage()  and
              then  applies  a  transformation using the colormap(s) to create
              TrueColor RGB values that it in turn inserts into bits  1-24  of
              the  framebuffer.  This creates a depth 24 "view" of the display
              that is then exported via VNC.

              Conversely, for default depth 8 displays, the depth  24  regions
              are  read  by  XGetImage() and everything is transformed and in-
              serted into a depth 24 TrueColor framebuffer.

              Note that even if there are *no* depth  24  visuals  or  windows
              (i.e.  pure  8bpp), this mode is potentially an improvement over
              -flashcmap because it avoids the flashing and shows each  window
              in the correct color.

              This  method  works  OK, but may still have bugs and it does hog
              resources.  If there are multiple 8bpp windows  using  different
              colormaps, one may have to iconify all but one for the colors to
              be correct.

              There may be painting errors for clipping and switching  between
              windows  of  depths  8 and 24.  Heuristics are applied to try to
              minimize the painting errors.  One can also press 3 Alt_L's in a
              row  to  refresh the screen if the error does not repair itself.
              Also the option -fixscreen 8=3.0 or -fixscreen V=3.0 may be used
              to periodically refresh the screen at the cost of bandwidth (ev-
              ery 3 sec for this example).

              The [opts] string can contain the following settings.   Multiple
              settings are separated by commas.

              For  for  some  X servers with default depth 24 a speedup may be
              achieved via the option "nogetimage".   This  enables  a  scheme
              were  XGetImage()  is  not  used to retrieve the 8bpp data.  In-
              stead, it assumes that the 8bpp data is in  bits  25-32  of  the
              32bit  X  pixels.   There  is  no  requirement that the X server
              should put the data there for our poll requests, but some do and
              so  the  extra steps to retrieve it can be skipped.  Tested with
              mga driver with XFree86/Xorg.  For the default depth 8 case this
              option is ignored.

              To  adjust how often XGetImage() is used to poll the non-default
              visual regions for changes, use the option "poll=t" where "t" is
              a floating point time.  (default: 0.05)

              Setting  the  option  "level2" will limit the search for non-de-
              fault visual windows to two levels from  the  root  window.   Do
              this on slow machines where you know the window manager only im-
              poses one extra window between the app window and the root  win-
              dow.

              Also for very slow machines use "cachewin=t" where t is a float-
              ing point amount of time to cache XGetWindowAttributes  results.
              E.g. cachewin=5.0.  This may lead to the windows being unnoticed
              for this amount of time when deiconifying, painting errors, etc.

              While testing on a very old SS20 these  options  gave  tolerable
              response:  -8to24 poll=0.2,cachewin=5.0. For this machine -over-
              lay is supported and gives better response.

              Debugging for this mode  can  be  enabled  by  setting  "dbg=1",
              "dbg=2", or "dbg=3".

       -24to32

              Very  rare  problem: if the framebuffer (X display or -rawfb) is
              24bpp instead of the usual 32bpp, then dynamically transform the
              pixels  to  32bpp.  This will be slower, but can be used to work
              around problems where VNC  viewers  cannot  handle  24bpp  (e.g.
              "main:  setPF:  not  8,  16  or 32 bpp?").  See the FAQ for more
              info.

              In the case of -rawfb mode, the pixels are directly modified  by
              inserting  a 0 byte to pad them out to 32bpp.  For X displays, a
              kludge is done that  is  equivalent  to  "-noshm  -visual  True-
              Color:32".   (If  better  performance  is needed for the latter,
              feel free to ask).

       -scale fraction

              Scale the framebuffer by factor fraction.  Values  less  than  1
              shrink the fb, larger ones expand it. Note: the image may not be
              sharp and response may be slower.  If fraction contains a  deci-
              mal  point  "." it is taken as a floating point number, alterna-
              tively the notation "m/n" may be used to  denote  fractions  ex-
              actly, e.g. -scale 2/3

              To  scale  asymmetrically  in the horizontal and vertical direc-
              tions, specify a  WxH  geometry  to  stretch  to:  e.g.  '-scale
              1024x768', or also '-scale 0.9x0.75'

              Scaling  Options: can be added after fraction via ":", to supply
              multiple ":" options use commas.  If  you  just  want  a  quick,
              rough  scaling  without blending, append ":nb" to fraction (e.g.
              -scale 1/3:nb).  No blending is the  default  for  8bpp  indexed
              color, to force blending for this case use ":fb".

              To  disable  -scrollcopyrect  and -wirecopyrect under -scale use
              ":nocr".  If you need to to enable them  use  ":cr"  or  specify
              them  explicitly  on  the  command  line.  If a slow link is de-
              tected, ":nocr" may be applied automatically.  Default: :cr

              More esoteric options: for  compatibility  with  vncviewers  the
              scaled  width is adjusted to be a multiple of 4: to disable this
              use ":n4".  ":in" use interpolation scheme even when  shrinking,
              ":pad"  pad  scaled  width and height to be multiples of scaling
              denominator (e.g. 3 for 2/3).

       -geometry WxH

              Same as -scale WxH

       -scale_cursor frac

              By default if -scale is supplied the cursor shape is  scaled  by
              the same factor.  Depending on your usage, you may want to scale
              the cursor independently of the screen or not at  all.   If  you
              specify  -scale_cursor the cursor will be scaled by that factor.
              When using -scale mode to keep the cursor at its "natural"  size
              use  "-scale_cursor  1".   Most of the ":" scaling options apply
              here as well.

       -viewonly

              All VNC clients can only watch (default off).

       -shared

              VNC display is shared, i.e. more than one viewer can connect  at
              the same time (default off).

       -once

              Exit  after the first successfully connected viewer disconnects,
              opposite of -forever. This is the Default.

       -forever

              Keep listening for more connections rather than exiting as  soon
              as the first client(s) disconnect. Same as -many

              To get the standard non-shared VNC behavior where when a new VNC
              client connects the existing VNC client is dropped use:  -never-
              shared  -forever   This method can also be used to guard against
              hung TCP connections that do not go away.

       -loop

              Create an outer loop restarting the x11vnc process  whenever  it
              terminates.   -bg  and  -inetd are ignored in this mode (however
              see -loopbg below).

              Useful for continuing  even  if  the  X  server  terminates  and
              restarts (at that moment the process will need permission to re-
              connect to the new X server of course).

              Use, e.g., -loop100 to sleep  100  millisecs  between  restarts,
              etc.   Default  is  2000ms (i.e. 2 secs) Use, e.g. -loop300,5 to
              sleep 300 ms and only loop 5 times.

              If -loopbg (plus any numbers) is specified  instead,  the  "-bg"
              option  is  implied  and the mode approximates inetd(8) usage to
              some degree.  In this case when it goes into the background  any
              listening  sockets  (i.e.  ports  5900, 5800) are closed, so the
              next one in the loop can use them.  This mode will  only  be  of
              use  if  a  VNC client (the only client for that process) is al-
              ready connected before the process goes into the background, for
              example,  usage of -display WAIT:.., -svc, and -connect can make
              use of this "poor man's" inetd mode.  The default wait  time  is
              500ms  in  this  mode.   This  usage could use useful:  -svc -bg
              -loopbg

       -timeout n

              Exit unless a client connects within the first n  seconds  after
              startup.

              If there have been no connection attempts after n seconds x11vnc
              exits immediately.  If a client is trying to connect but has not
              progressed  to the normal operating state, x11vnc gives it a few
              more seconds to finish and exits if it does not make it  to  the
              normal state.

              For reverse connections via -connect or -connect_or_exit a time-
              out of n seconds will be set for all reverse connects.   If  the
              connect timeout alarm goes off, x11vnc will exit immediately.

       -sleepin n

              At  startup  sleep  n  seconds  before proceeding (e.g. to allow
              redirs and listening clients to start up)

              If a range is given: '-sleepin min-max', a random value  between
              min and max is slept. E.g. '-sleepin 0-20' and '-sleepin 10-30'.
              Floats are allowed too.

       -inetd

              Launched by inetd(8): stdio instead of listening socket.   Note:
              if you are not redirecting stderr to a log file (via shell 2> or
              -o option) you MUST also specify the -q  option,  otherwise  the
              stderr  goes to the viewer which will cause it to abort.  Speci-
              fying both -inetd and -q and no -o will automatically close  the
              stderr.

       -tightfilexfer

              Enable the TightVNC file transfer extension. Note that that when
              the -viewonly option is supplied all  file  transfers  are  dis-
              abled.  Also clients that log in viewonly cannot transfer files.
              However, if the remote control mechanism is used to  change  the
              global or per-client viewonly state the filetransfer permissions
              will NOT change.

              IMPORTANT: please understand if -tightfilexfer is specified  and
              you  run x11vnc as root for, say, inetd or display manager (gdm,
              kdm, ...) access and you do not have it  switch  users  via  the
              -users  option,  then  VNC  Viewers  that connect are able to do
              filetransfer reads and writes as *root*.

              Also, tightfilexfer is disabled in -unixpw mode.

       -ultrafilexfer

              Note: to enable UltraVNC filetransfer and to get it to work  you
              probably need to supply these LibVNCServer options: "-rfbversion
              3.6 -permitfiletransfer" "-ultrafilexfer" is an alias  for  this
              combination.

              IMPORTANT:  please understand if -ultrafilexfer is specified and
              you run x11vnc as root for, say, inetd or display manager  (gdm,
              kdm,  ...)  access  and  you do not have it switch users via the
              -users option, then VNC Viewers that  connect  are  able  to  do
              filetransfer reads and writes as *root*.

              Note  that  sadly  you cannot do both -tightfilexfer and -ultra-
              filexfer at the same time because the  latter  requires  setting
              the version to 3.6 and tightvnc will not do filetransfer when it
              sees that version number.

       -http

              Instead of using -httpdir (see below) to specify where the  Java
              vncviewer applet is, have x11vnc try to *guess* where the direc-
              tory is by looking relative to the program location and in stan-
              dard  locations  (/usr/local/share/x11vnc/classes,  etc).  Under
              -ssl or -stunnel the ssl classes subdirectory is sought.

       -http_ssl

              As -http, but force lookup for ssl classes subdir.

              Note that for HTTPS, single-port Java applet  delivery  you  can
              set X11VNC_HTTPS_DOWNLOAD_WAIT_TIME to the max number of seconds
              to wait for the applet download to finish.  The default is 15.

       -avahi

              Use the Avahi/mDNS  ZeroConf  protocol  to  advertise  this  VNC
              server  to  the  local network. (Related terms: Rendezvous, Bon-
              jour).  Depending on your setup, you may need  to  start  avahi-
              daemon and open udp port 5353 in your firewall.

              You   can   set   X11VNC_AVAHI_NAME,  X11VNC_AVAHI_HOST,  and/or
              X11VNC_AVAHI_PORT environment variables to override the  default
              values.  For example: -env X11VNC_AVAHI_NAME=wally

              If the avahi API cannot be found at build time, a helper program
              like avahi- publish(1) or dns- sd(1) will be tried

       -mdns

              Same as -avahi.

       -zeroconf

              Same as -avahi.

       -connect string

              For use with "vncviewer -listen" reverse connections.  If string
              has  the  form "host" or "host:port" the connection is made once
              at startup.

              Use commas for a list of host's and host:port's.  E.g.  -connect
              host1,host2 or host1:0,host2:5678.  Note that to reverse connect
              to multiple hosts at the same time you will likely need to  also
              supply: -shared

              Note  that  unlike most vnc servers, x11vnc will require a pass-
              word for reverse as well as for forward connections.   (provided
              password  auth  has  been  enabled, -rfbauth, etc) If you do not
              want  to  require  a  password  for  reverse   connections   set
              X11VNC_REVERSE_CONNECTION_NO_AUTH=1  in  your environment before
              starting x11vnc.

              If string contains "/" it is instead interpreted as  a  file  to
              periodically  check  for  new hosts.  The first line is read and
              then the file is truncated.  Be careful about  the  location  of
              this file if x11vnc is running as root (e.g. via gdm(1) , etc).

              Repeater  mode:  Some  services provide an intermediate "vnc re-
              peater":  http://www.uvnc.com/addons/repeater.html   (and   also
              http://koti.mbnet.fi/jtko/  for  linux  port)  that  acts  as  a
              proxy/gateway.  Modes like these require an initial string to be
              sent  for  the  reverse  connection  before  the VNC protocol is
              started.  Here are the ways to do this:

              -connect           pre=some_string+host:port            -connect
              pre128=some_string+host:port -connect repeater=ID:1234+host:port
              -connect repeater=23.45.67.89::5501+host:port

              SSVNC notation is also supported:

              -connect repeater://host:port+ID:1234

              As with normal -connect usage, if the repeater port is not  sup-
              plied 5500 is assumed.

              The  basic  idea is between the special tag, e.g. "pre=" and "+"
              is the pre-string to be sent.  Note that in this case  host:port
              is  the  repeater  server, NOT the vnc viewer.  Somehow the pre-
              string tells the repeater server how to find the vnc viewer  and
              connect you to it.

              In  the  case pre=some_string+host:port, "some_string" is simply
              sent. In the case preNNN=some_string+host:port "some_string"  is
              sent  in  a  null padded buffer of length NNN.  repeater= is the
              same as pre250=, this is the ultravnc repeater buffer size.

              Strings like "\n" and "\r", etc. are  expanded  to  newline  and
              carriage  return.   "\c"  is  expanded  to "," since the connect
              string is comma separated.

              See also the -proxy option below for additional  ways  to  plumb
              reverse connections.

              Reverse  SSL: using -connect in -ssl mode makes x11vnc act as an
              SSL client (initiates SSL connection) rather than an SSL server.
              The  idea is x11vnc might be connecting to stunnel on the viewer
              side with the viewer in listening mode.  If you do not want this
              behavior,  use -env X11VNC_DISABLE_SSL_CLIENT_MODE=1.  With this
              the viewer side can act as the SSL client as  it  normally  does
              for forward connections.

              Reverse SSL Repeater mode:  This will work, but note that if the
              VNC Client does any sort of a 'Fetch Cert'  action  before  con-
              necting,  then  the Repeater will likely drop the connection and
              both sides will need to restart.   Consider  the  use  of  -con-
              nect_or_exit and -loop300,2 to have x11vnc reconnect once to the
              repeater after the fetch.  You will probably also want to supply
              -sslonly  to  avoid  x11vnc thinking the delay in response means
              the  connection  is   VeNCrypt.    The   env   var   X11VNC_DIS-
              ABLE_SSL_CLIENT_MODE=1  discussed above may also be useful (i.e.
              the viewer can do a forward connection as it normally does.)

              IPv6: as of x11vnc 0.9.10 the -connect option should connect  to
              IPv6 hosts properly.  If there are problems you can disable IPv6
              by setting -DX11VNC_IPV6=0 in  CPPFLAGS  when  configuring.   If
              there  problems  connecting  to IPv6 hosts consider a relay like
              the included inet6to4 script or the -proxy option.

       -connect_or_exit str

              As with -connect, except if none of the reverse connections suc-
              ceed, then x11vnc shuts down immediately

              An easier to type alias for this option is '-coe'

              By the way, if you do not want x11vnc to listen on ANY interface
              use -rfbport 0  which is handy for the -connect_or_exit mode.

       -proxy string

              Use proxy in string (e.g. host:port) as a proxy for  making  re-
              verse connections (-connect or -connect_or_exit options).

              Web proxies are supported, but note by default most of them only
              support destination connections to ports 443  or  563,  so  this
              might  not  be  very  useful (the viewer would need to listen on
              that port or the router would have to do a port redirection).

              A  web  proxy  may  be  specified  by  either   "host:port"   or
              "http://host:port"  (the port is required even if it is the com-
              mon choices 80 or 8080)

              SOCKS4, SOCKS4a, and SOCKS5 are also supported.   SOCKS  proxies
              normally  do  not have restrictions on the destination port num-
              ber.

              Use a format like this: socks://host:port or socks5://host:port.
              Note  that  ssh  -D  does not support SOCKS4a, so use socks5://.
              For socks:// SOCKS4 is used on a numerical IP  and  "localhost",
              otherwise  SOCKS4a is used (and so the proxy tries to do the DNS
              lookup).

              An experimental mode is "-proxy http://host:port/..."  Note  the
              "/"  after  the  port  that  distinguishes  it from a normal web
              proxy.  The port must be supplied even if it is the default  80.
              For  this mode a GET is done to the supplied URL with the string
              host=H&port=P appended.  H and P will be  the  -connect  reverse
              connect  host and port.  Use the string "__END__" to disable the
              appending.  The basic idea here is that maybe  some  cgi  script
              provides  the actual viewer hookup and tunnelling.  How to actu-
              ally achieve this within cgi, php, etc. is not clear...  A  cus-
              tom web server or apache module would be straight-forward.

              Another  experimental  mode is "-proxy ssh://user@host" in which
              case a SSH tunnel is used for  the  proxying.   "user@"  is  not
              needed  unless your unix username is different on "host".  For a
              non-standard SSH port use ssh://user@host:port.  If proxies  are
              chained  (see next paragraph) then the ssh one must be the first
              one.  If ssh-agent is not active, then the ssh password needs to
              be entered in the terminal where x11vnc is running.  Examples:

              -connect localhost:0 -proxy ssh://me@friends-pc:2222

              -connect snoopy:0 -proxy ssh://ssh.company.com

              Multiple  proxies  may  be chained together in case one needs to
              ricochet off of a number of  hosts  to  finally  reach  the  VNC
              viewer.   Up to 3 may be chained, separate them by commas in the
              order    they    are    to    be    connected     to.      E.g.:
              http://host1:port1,socks5://host2:port2     or    three    like:
              first,second,third

              IPv6: as of x11vnc 0.9.10 the -proxy option  should  connect  to
              IPv6 hosts properly.  If there are problems you can disable IPv6
              by setting -DX11VNC_IPV6=0 in  CPPFLAGS  when  configuring.   If
              there  problems  connecting  to IPv6 hosts consider a relay like
              the included inet6to4 script.

       -vncconnect, -novncconnect

              Monitor the VNC_CONNECT X property set by the standard VNC  pro-
              gram  vncconnect(1).   When  the  property  is  set to "host" or
              "host:port" establish a reverse connection.  Using xprop(1)  in-
              stead of vncconnect may work (see the FAQ).  The -remote control
              mechanism uses  X11VNC_REMOTE  channel,  and  this  option  dis-
              ables/enables it as well.  Default: -vncconnect

              To  use  different  names for these X11 properties (e.g. to have
              separate communication channels for  multiple  x11vnc's  on  the
              same display) set the VNC_CONNECT or X11VNC_REMOTE env. vars. to
              the string you want, for example: -env  X11VNC_REMOTE=X11VNC_RE-
              MOTE_12345  Both  sides  of the channel must use the same unique
              name.  The same can be done for the internal X11VNC_TICKER prop-
              erty (heartbeat and timestamp) if desired.

       -allow host1[,host2..]

              Only allow client connections from hosts matching the comma sep-
              arated list of hostnames or IP addresses.  Can also be a numeri-
              cal  IP  prefix,  e.g. "192.168.100."  to match a simple subnet,
              for more control build LibVNCServer with  libwrap  support  (See
              the  FAQ).   If  the  list contains a "/" it instead is a inter-
              preted as a file containing addresses or prefixes  that  is  re-
              read  each  time  a new client connects.  Lines can be commented
              out with the "#" character in the usual way.

              -allow applies in -ssl mode, but not in -stunnel mode.

              IPv6: as of x11vnc 0.9.10 a host can be specified in IPv6 numer-
              ical format, e.g. 2001:4860:b009::93.

       -localhost

              Basically the same as "-allow 127.0.0.1".

              Note:  if  you  want  to restrict which network interface x11vnc
              listens on, see the -listen option below.  E.g. "-listen  local-
              host"  or "-listen 192.168.3.21".  As a special case, the option
              "-localhost" implies "-listen localhost".

              A rare case, but for non-localhost -listen usage, if you use the
              remote  control  mechanism  (-R) to change the -listen interface
              you may need to manually adjust the -allow list (and vice versa)
              to  avoid  situations where no connections (or too many) are al-
              lowed.

              If you do not want x11vnc to listen on ANY interface  (evidently
              you  are  using -connect or -connect_or_exit, or plan to use re-
              mote control: -R connect:host), use -rfbport 0

              IPv6: if IPv6 is supported, this  option  automatically  implies
              the IPv6 loopback address '::1' as well.

       -unixsock str

              Listen on the unix socket (AF_UNIX) 'str' for connections.  This
              mode is for either local connections or a tunnel endpoint  where
              one  wants the file permission of the unix socket file to deter-
              mine what can connect to it.  (This currently requires  an  edit
              to  libvnserver/rfbserver.c:  comment  out  lines  310  and 311,
              'close(sock)' and 'return NULL' in rfbserver.c  after  the  set-
              sockopt()  call.)  Note  that to disable all tcp listening ports
              specify '-rfbport 0' and should be useful with this mode.  Exam-
              ple: mkdir ~/s; chmod 700 ~/s; x11vnc -unixsock ~/s/mysock -rfb-
              port 0 ...  The SSVNC unix vncviewer can connect to  unix  sock-
              ets.

       -listen6 str

              When in IPv6 listen mode "-6", listen only on the network inter-
              face with address str.  It also works for link  scope  addresses
              (fe80::219:dbff:fee5:3f92%eth0)  and IPv6 hostname strings (e.g.
              ipv6.google.com.)  Use LibVNCServer -listen option for the  IPv4
              interface.

       -nolookup

              Do  not  use  gethostbyname() or gethostbyaddr() to look up host
              names or IP numbers.  Use this if name resolution is incorrectly
              set up and leads to long pauses as name lookups time out, etc.

       -input string

              Fine tuning of allowed user input.  If string does not contain a
              comma "," the tuning applies only to normal clients.   Otherwise
              the part before "," is for normal clients and the part after for
              view-only clients.  "K" is for Keystroke input, "M"  for  Mouse-
              motion  input,  "B" for Button-click input, "C" is for Clipboard
              input, and "F" is for  File  transfer  (ultravnc  only).   Their
              presence in the string enables that type of input.  E.g. "-input
              M" means normal users can only move the mouse and   "-input  KM-
              BCF,M" lets normal users do anything and enables view-only users
              to move the  mouse.   This  option  is  ignored  when  a  global
              -viewonly is in effect (all input is discarded in that case).

       -grabkbd

              When VNC viewers are connected, attempt to the grab the keyboard
              so a (non-malicious) user sitting at the physical display is not
              able  to enter keystrokes.  This method uses XGrabKeyboard(3X11)
              and so it is not secure and does not rule out the person at  the
              physical  display  injecting  keystrokes  by flooding the server
              with them, grabbing the keyboard himself, etc.  Some  degree  of
              cooperation  from the person at the display is assumed.  This is
              intended for remote help-desk or educational usage modes.

              Note: on  some  recent  (12/2010)  X  servers  and/or  desktops,
              -grabkbd  no  longer  works: it prevents the window manager from
              resizing windows and  similar  things.   Try  -ungrabboth  below
              (might not work.)

       -grabptr

              As -grabkbd, but for the mouse pointer using XGrabPointer(3X11).
              Unfortunately due to the way the X server works, the  mouse  can
              still  be  moved around by the user at the physical display, but
              he will not be able to change window focus with it.   Also  some
              window  managers  that  call XGrabServer(3X11) for resizes, etc,
              will act on the local user's input.  Again, some degree of coop-
              eration from the person at the display is assumed.

       -ungrabboth

              Whenever there is any input (either keyboard or pointer), ungrab
              *both* the keyboard and the pointer  while  injecting  the  syn-
              thetic  input.   This is to allow window managers, etc. a chance
              to grab.

       -grabalways

              Apply both -grabkbd and -grabptr even when no  VNC  viewers  are
              connected.  If you only want one of them, use the -R remote con-
              trol to turn the other back on, e.g. -R nograbptr.

       -viewpasswd string

              Supply a 2nd password for view-only logins.  The -passwd  (full-
              access) password must also be supplied.

       -passwdfile filename

              Specify the LibVNCServer password via the first line of the file
              filename (instead of via -passwd on the command line where  oth-
              ers might see it via ps(1) ).

              See the descriptions below for how to supply multiple passwords,
              view-only passwords, to specify external programs  for  the  au-
              thentication, and other features.

              If  the filename is prefixed with "rm:" it will be removed after
              being read.  Perhaps this is useful in limiting the  readability
              of  the file.  In general, the password file should not be read-
              able by untrusted users (BTW: neither should  the  VNC  -rfbauth
              file: it is NOT encrypted, only obscured with a fixed key).

              If the filename is prefixed with "read:" it will periodically be
              checked for changes and reread.  It is guaranteed to  be  reread
              just  when  a  new  client connects so that the latest passwords
              will be used.

              If filename is prefixed with "cmd:" then the  string  after  the
              ":"  is  run  as  an external command: the output of the command
              will be interpreted as if it were read from a password file (see
              below).  If the command does not exit with 0, then x11vnc termi-
              nates immediately.  To specify more than 1000 passwords this way
              set  X11VNC_MAX_PASSWDS before starting x11vnc.  The environment
              variables are set as in -accept.

              Note that due to the VNC protocol only the first 8 characters of
              a password are used (DES key).

              If  filename  is  prefixed with "custom:" then a custom password
              checker is supplied as an external command  following  the  ":".
              The  command  will  be  run when a client authenticates.  If the
              command exits with 0 the client is accepted, otherwise it is re-
              jected.  The environment variables are set as in -accept.

              The standard input to the custom command will be a decimal digit
              "len" followed by a newline. "len" specifies the challenge  size
              and  is usually 16 (the VNC spec).  Then follows len bytes which
              is the random challenge string that was sent to the client. This
              is then followed by len more bytes holding the client's response
              (i.e. the challenge string encrypted via DES with the user pass-
              word in the standard situation).

              The  "custom:"  scheme  can be useful to implement dynamic pass-
              words or to implement methods where longer passwords and/or dif-
              ferent  encryption algorithms are used.  The latter will require
              customizing the VNC client as well.  One could create an  MD5SUM
              based scheme for example.

              File format for -passwdfile:

              If multiple non-blank lines exist in the file they are all taken
              as valid passwords.  Blank lines are  ignored.   Password  lines
              may  be "commented out" (ignored) if they begin with the charac-
              ter "#" or the line contains the string "__SKIP__".   Lines  may
              be annotated by use of the "__COMM__" string: from it to the end
              of the line is ignored.  An empty password may be specified  via
              the  "__EMPTY__"  string  on  a line by itself (note your viewer
              might not accept empty passwords).

              If the string "__BEGIN_VIEWONLY__" appears on a line by  itself,
              the  remaining passwords are used for viewonly access.  For com-
              patibility, as a special case if  the  file  contains  only  two
              password  lines  the  2nd  one  is  automatically  taken  as the
              viewonly password.   Otherwise  the  "__BEGIN_VIEWONLY__"  token
              must be used to have viewonly passwords.  (tip: make the 3rd and
              last line be "__BEGIN_VIEWONLY__" to have  2  full-access  pass-
              words)

       -showrfbauth filename

              Print  to  the  screen the obscured VNC password kept in the rf-
              bauth file filename and then exit.

       -unixpw [list]

              Use Unix username and password authentication.  x11vnc will  use
              the  su(1)  program to verify the user's password.  [list] is an
              optional comma separated list of allowed Unix usernames.  If the
              [list] string begins with the character "!" then the entire list
              is taken as an exclude list.  See  below  for  per-user  options
              that can be applied.

              A  familiar  "login:" and "Password:" dialog is presented to the
              user on a black screen inside the vncviewer.  The connection  is
              dropped  if  the  user fails to supply the correct password in 3
              tries or does not send one before a 45 second timeout.  Existing
              clients are view-only during this period.

              If  the first character received is "Escape" then the unix user-
              name will not be displayed after "login:" as it is typed.   This
              could  be  of  use  for  VNC viewers that automatically type the
              username and password.

              Since the detailed behavior of su(1) can vary from OS to OS  and
              for  local  configurations,  test  the mode before deployment to
              make sure it is working properly.  x11vnc  will  attempt  to  be
              conservative and reject a login if anything abnormal occurs.

              One  case  to note: FreeBSD and the other BSD's by default it is
              impossible for the user running x11vnc  to  validate  his  *own*
              password  via  su(1)  (commenting  out  the pam_self.so entry in
              /etc/pam.d/su eliminates this behavior).  So  the  x11vnc  login
              will always *FAIL* for this case (even when the correct password
              is supplied).

              A possible workaround for this on *BSD would be to start  x11vnc
              as  root  with the "-users +nobody" option to immediately switch
              to user nobody where the su'ing will proceed normally.

              Another source of potential problems are PAM modules that prompt
              for  extra info, e.g. password aging modules.  These logins will
              fail as well even when the correct password is supplied.

              **IMPORTANT**: to prevent the Unix password being sent in *clear
              text*  over the network, one of two schemes will be enforced: 1)
              the -ssl builtin SSL mode, or 2)  require  both  -localhost  and
              -stunnel be enabled.

              Method  1)  ensures  the traffic is encrypted between viewer and
              server.  A PEM file will be required, see the  discussion  under
              -ssl  below (under some circumstances a temporary one can be au-
              tomatically generated).

              Method 2) requires the viewer connection to appear to come  from
              the  same  machine x11vnc is running on (e.g. from a ssh -L port
              redirection).  And that the -stunnel SSL mode be  used  for  en-
              cryption  over the network. (see the description of -stunnel be-
              low).

              Note: as a convenience, if you ssh(1) in  and  start  x11vnc  it
              will check if the environment variable SSH_CONNECTION is set and
              appears reasonable.  If it does, then the -ssl or  -stunnel  re-
              quirement  will be dropped since it is assumed you are using ssh
              for the encrypted tunnelling.   -localhost  is  still  enforced.
              Use  -ssl  or -stunnel to force SSL usage even if SSH_CONNECTION
              is set.

              To override the above restrictions you can set environment vari-
              ables before starting x11vnc:

              Set  UNIXPW_DISABLE_SSL=1  to  disable  requiring either -ssl or
              -stunnel (as under SSH_CONNECTION.)  Evidently you will be using
              a different method to encrypt the data between the vncviewer and
              x11vnc: perhaps ssh(1) or an IPSEC VPN. -localhost is still  en-
              forced (however, see the next paragraph.)

              Set  UNIXPW_DISABLE_LOCALHOST=1  to  disable  the -localhost re-
              quirement in -unixpw modes.  One should never do this (i.e.  al-
              low the Unix passwords to be sniffed on the network.)  This also
              disables the localhost requirement for reverse connections  (see
              below.)

              Note  that  use  of  -localhost  with ssh(1) (and no -unixpw) is
              roughly the same as requiring a Unix user login  (since  a  Unix
              password or the user's public key authentication is used by sshd
              on the machine where x11vnc runs and only local connections from
              that machine are accepted).

              Regarding reverse connections (e.g. -R connect:host and -connect
              host), when the -localhost constraint is in effect then  reverse
              connections  can  only  be  used  to connect to the same machine
              x11vnc is running on (default port 5500).  Please use a  ssh  or
              stunnel port redirection to the viewer machine to tunnel the re-
              verse connection over an encrypted channel.

              In -inetd mode the Method 1) will be enforced  (not  Method  2).
              With  -ssl  in  effect reverse connections are disabled.  If you
              override this via env. var, be sure to also use encryption  from
              the  viewer  to  inetd.  Tip: you can also have your own stunnel
              spawn x11vnc in -inetd mode (thereby bypassing inetd).  See  the
              FAQ for details.

              The  user  names in the comma separated [list] may have per-user
              options after a ":", e.g. "fred:opts" where "opts" is a "+" sep-
              arated   list  of  "viewonly",  "fullaccess",  "input=XXXX",  or
              "deny", e.g. "karl,wally:viewonly,boss:input=M".   For  "input="
              it is the K,M,B,C described under -input.

              If  an item in the list is "*" that means those options apply to
              all users.  It ALSO implies all users are allowed to log in  af-
              ter  supplying  a valid password.  Use "deny" to explicitly deny
              some users if you use "*" to set a global option.  If [list] be-
              gins  with the "!" character then "*" is ignored for checking if
              the user is allowed, but the option values associated with it do
              apply as normal.

              There  are  also some utilities for checking passwords if [list]
              starts with the "%" character.  See the quick_pw() function  for
              more details.  Description: "%-" or "%stdin" means read one line
              from stdin.  "%env" means it is in $UNIXPW env var.   A  leading
              "%/"  or  "%."  means read the first line from the filename that
              follows after the % character. % by itself means prompt for  the
              username  and  password.   Otherwise:  %user:pass   E.g. -unixpw
              %fred:swordfish For the other cases user:pass is read  from  the
              indicated  source.   If  the  password  is  correct  'Y user' is
              printed and the program exit code is 0.  If the password is  in-
              correct  it prints 'N user' and the exit code is 1.  If there is
              some other error the exit  code  is  2.   This  feature  enables
              x11vnc  to  be  a  general  unix user password checking tool; it
              could be used from scripts or other programs.  These %  password
              checks also apply to the -unixpw_nis and -unixpw_cmd options.

              For  the % password check, if the env. var. UNIXPW_CMD is set to
              a command then it is run as the user (assuming the  password  is
              correct.)  The output of the command is not printed, the program
              or script must manage that by some other means.  The  exit  code
              of  x11vnc  will  depend on the exit code of the command that is
              run.

              Use -nounixpw to disable unixpw mode if it was  enabled  earlier
              in the cmd line (e.g. -svc mode)

       -unixpw_nis [list]

              As  -unixpw  above,  however do not use su(1) but rather use the
              traditional getpwnam(3) + crypt(3) method to  verify  passwords.
              All of the above -unixpw options and constraints apply.

              This  mode  requires  that  the encrypted passwords be readable.
              Encrypted passwords stored in /etc/shadow will  be  inaccessible
              unless x11vnc is run as root.

              This is called "NIS" mode simply because in most NIS setups user
              encrypted passwords are accessible (e.g. "ypcat passwd")  by  an
              ordinary user and so that user can authenticate ANY user.

              NIS is not required for this mode to work (only that getpwnam(3)
              return the encrypted password is required), but it  is  unlikely
              it  will work (as an ordinary user) for most modern environments
              unless NIS is available.  On the other hand, when x11vnc is  run
              as  root it will be able to to access /etc/shadow even if NIS is
              not available (note running as root is often done  when  running
              x11vnc from inetd and xdm/gdm/kdm).

              Looked  at  another  way,  if  you  do not want to use the su(1)
              method provided by  -unixpw  (i.e.  su_verify()),  you  can  run
              x11vnc as root and use -unixpw_nis.  Any users with passwords in
              /etc/shadow can then be authenticated.

              In -unixpw_nis mode, under no  circumstances  is  x11vnc's  user
              password  verifying  function based on su called (i.e. the func-
              tion su_verify() that runs /bin/su in a pseudoterminal to verify
              passwords.)  However, if -unixpw_nis is used in conjunction with
              the -find and -create -display WAIT:... modes then, if x11vnc is
              running  as  root,  /bin/su  may be called externally to run the
              find or create commands.

       -unixpw_cmd cmd

              As -unixpw above, however do not use su(1) but  rather  run  the
              externally  supplied  command  cmd.  The first line of its stdin
              will be the username and the second line the received  password.
              If  the  command exits with status 0 (success) the VNC user will
              be accepted.  It will be rejected for any other return status.

              Dynamic passwords and non-unix passwords, e.g. LDAP, can be  im-
              plemented  this way by providing your own custom helper program.
              Note that the remote viewer is given 3 tries to enter  the  cor-
              rect  password,  and  so the program may be called in a row that
              many (or more) times.

              If a list of allowed users is needed to limit who  can  log  in,
              use -unixpw [list] in addition to this option.

              In  FINDDISPLAY and FINDCREATEDISPLAY modes the cmd will also be
              run with the RFB_UNIXPW_CMD_RUN env. var.  non-empty and set  to
              the  corresponding  display  find/create command.  The first two
              lines of input are the username and passwd as in the normal case
              described  above.  To support FINDDISPLAY and FINDCREATEDISPLAY,
              cmd should run the requested  command  as  the  user  (and  most
              likely refusing to run it if the password is not correct.)  Here
              is an example script (note it has  a  hardwired  bogus  password
              "abc"!)

              #!/bin/sh # Example x11vnc -unixpw_cmd script.  # Read the first
              two lines of stdin (user and passwd) read user read pass

              debug=0 if [ $debug = 1 ]; then echo  "user:  $user"  1>&2  echo
              "pass: $pass" 1>&2 env | egrep -i 'rfb|vnc' 1>&2 fi

              #  Check  if the password is valid.  # (A real example would use
              ldap lookup, etc!)  if [ "X$pass" != "Xabc" ]; then exit  1    #
              incorrect password fi

              if  [  "X$RFB_UNIXPW_CMD_RUN"  = "X" ]; then exit 0    # correct
              password else # Run the requested  command  (finddisplay)  if  [
              $debug  = 1 ]; then echo "run: $RFB_UNIXPW_CMD_RUN" 1>&2 fi exec
              /bin/su - "$user" -c "$RFB_UNIXPW_CMD_RUN" fi

              In -unixpw_cmd mode, under no  circumstances  is  x11vnc's  user
              password  verifying  function based on su called (i.e. the func-
              tion su_verify() that runs /bin/su in a pseudoterminal to verify
              passwords.)   It  is  up  to  the supplied unixpw_cmd to do user
              switching if desired and if it has the permissions to do so.

       -find

              Find the user's display using FINDDISPLAY. This is an alias  for
              "-display WAIT:cmd=FINDDISPLAY".

              Note:  if  a  -display  occurs later on the command line it will
              override the -find setting.

              For this and the next few options see -display  WAIT:...   below
              for all of the details.

       -finddpy

              Run  the  FINDDISPLAY  program,  print out the found display (if
              any)   and   exit.    Output   is   like:   DISPLAY=:0.0    DIS-
              PLAY=:0.0,XPID=12345  or DISPLAY=:0.0,VT=7.  XPID is the process
              ID of the found X server.  VT is the Linux virtual  terminal  of
              the X server.

       -listdpy

              Have the FINDDISPLAY program list all of your displays (i.e. all
              the X displays on the local machine that you have access  rights
              to).  x11vnc then exits.

       -findauth [disp]

              Apply the -find/-finddpy heuristics to try to guess the XAUTHOR-
              ITY file for DISPLAY 'disp'.  If 'disp' is  not  supplied,  then
              the  value  in the -display on the cmdline is used; failing that
              $DISPLAY is used; and failing that ":0" is  used.   x11vnc  then
              exits.

              If  nothing  is  printed out, that means no XAUTHORITY was found
              for 'disp'; i.e. failure.  If "XAUTHORITY=" is printed out, that
              means  use  the  default (i.e. do not set XAUTHORITY).  If "XAU-
              THORITY=/path/to/file" is printed out, then use that file.

              XDM/GDM/KDM: if you are running x11vnc as root and want to  find
              the  XAUTHORITY  before anyone has logged into an X session yet,
              use: x11vnc -env FD_XDM=1 -findauth ...  (This  will  also  find
              the  XAUTHORITY if a user is already logged into the X session.)
              When running as root, FD_XDM=1 will  be  tried  if  the  initial
              -findauth fails.

       -create

              First  try to find the user's display using FINDDISPLAY, if that
              doesn't succeed create an X session  via  the  FINDCREATEDISPLAY
              method.   This is an alias for "-display WAIT:cmd=FINDCREATEDIS-
              PLAY-Xvfb".

              Note: if a -display occurs later on the  command  line  it  will
              override the -create setting.

              SSH  NOTE: for both -find and -create you can (should!)  add the
              "-localhost" option to force SSH tunnel access.

       -xdummy

              As in -create, except Xdummy instead of Xvfb.

       -xvnc

              As in -create, except Xvnc instead of Xvfb.

       -xvnc_redirect

              As in -create, except Xvnc.redirect instead of Xvfb.

       -xdummy_xvfb

              Sets WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb

       -create_xsrv str

              Sets WAIT:cmd=FINDCREATEDISPLAY-<str>  Can be on  cmdline  after
              anything that sets WAIT:.. and other things (e.g. -svc, -xdmsvc)
              to adjust the X server list.   Example:  -svc  ...  -create_xsrv
              Xdummy,X

       -svc

              Terminal  services mode based on SSL access.  Alias for -display
              WAIT:cmd=FINDCREATEDISPLAY-Xvfb -unixpw -users unixpw= -ssl SAVE
              Also "-service".

              Note:  if  a  -display, -unixpw, -users, or -ssl occurs later on
              the command line it will override the -svc setting.

       -svc_xdummy

              As -svc except Xdummy instead of Xvfb.

       -svc_xvnc

              As -svc except Xvnc instead of Xvfb.

       -svc_xdummy_xvfb

              As -svc with Xdummy,Xvfb.

       -xdmsvc

              Display manager Terminal services mode based on SSL.  Alias  for
              -display  WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp  -unixpw  -users
              unixpw= -ssl SAVE  Also "-xdm_service".

              Note: if a -display, -unixpw, -users, or -ssl  occurs  later  on
              the command line it will override the -xdmsvc setting.

              To  create  a  session  a  user will have to first log in to the
              -unixpw dialog and then log in again to the XDM/GDM/KDM  prompt.
              Subsequent  re-connections  will  only require the -unixpw pass-
              word.  See the discussion under -display WAIT:... for  more  de-
              tails about XDM, etc configuration.

              Remember  to  enable XDMCP in the xdm-config, gdm.conf, or kdmrc
              configuration file.  See -display WAIT: for more info.

       -sshxdmsvc

              Display manager Terminal services mode based on SSH.  Alias  for
              -display WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp -localhost.

              The  -localhost  option  constrains connections to come in via a
              SSH tunnel (which will require a login).  To create a session  a
              user  will  also have to log into the XDM GDM KDM prompt. Subse-
              quent re-connections will only only require the SSH login.   See
              the  discussion  under  -display WAIT:... for more details about
              XDM, etc configuration.

              Remember to enable XDMCP in the xdm-config, gdm.conf,  or  kdmrc
              configuration file.  See -display WAIT: for more info.

       -unixpw_system_greeter

              Present a "Press 'Escape' for System Greeter" option to the con-
              necting VNC client in combined -unixpw and xdmcp  FINDCREATEDIS-
              PLAY modes (e.g. -xdmsvc).

              Normally  in  a  -unixpw mode the VNC client must supply a valid
              username and password to gain access.  However, if  -unixpw_sys-
              tem_greeter   is  supplied  AND  the  FINDCREATEDISPLAY  command
              matches 'xdmcp', then the user has the option  to  press  Escape
              and  then  get  a  XDM/GDM/KDM login/greeter panel instead. They
              will then  supply  a  username  and  password  directly  to  the
              greeter.

              Otherwise,  in xdmcp FINDCREATEDISPLAY mode the user must supply
              his username and password TWICE.  First to  the  initial  unixpw
              login  dialog, and second to the subsequent XDM/GDM/KDM greeter.
              Note that if the user re-connects and supplies his username  and
              password  in  the unixpw dialog the xdmcp greeter is skipped and
              he is connected directly to his  existing  X  session.   So  the
              -unixpw_system_greeter  option  avoids  the  extra password at X
              session creation time.

              Example:  x11vnc -xdmsvc -unixpw_system_greeter See -unixpw  and
              -display WAIT:... for more info.

              The  special  options  after  a colon at the end of the username
              (e.g. user:solid) described under -display WAIT:  are  also  ap-
              plied in this mode if they are typed in before the user hits Es-
              cape.  The username is ignored but the colon options are not.

              The default message is 2 lines in a small  font,  set  the  env.
              var.  X11VNC_SYSTEM_GREETER1=true  for  a  1  line  message in a
              larger font.

              If the user pressed Escape the FINDCREATEDISPLAY command will be
              run with the env. var. X11VNC_XDM_ONLY=1.

              Remember  to  enable XDMCP in the xdm-config, gdm.conf, or kdmrc
              configuration file.  See -display WAIT: for more info.

       -redirect port

              As in FINDCREATEDISPLAY-Xvnc.redirect mode except redirect imme-
              diately  (i.e.  without  X session finding or creation) to a VNC
              server listening on port. You can also supply host:port to redi-
              rect to a different machine.

              If  0  <= port < 200 it is taken as a VNC display (5900 is added
              to get the actual port), if port < 0 then -port is used.

              Probably the only reason to use the -redirect option is in  con-
              junction  with  SSL  support,  e.g. -ssl SAVE.  This provides an
              easy way to add SSL encryption to a VNC  server  that  does  not
              support SSL (e.g. Xvnc or vnc.so) In fact, the protocol does not
              even need to be VNC, and so "-rfbport port1 -ssl SAVE  -redirect
              host:port2" can act as a replacement for stunnel(1).

              This  mode  only allows one redirected connection.  The -forever
              option does not apply.  Use -inetd or -loop for persistent  ser-
              vice.

       -display WAIT:...

              A  special  usage  mode  for the normal -display option.  Useful
              with -unixpw, but can be used independently of it.  If the  dis-
              play  string  begins  with  WAIT:  then x11vnc waits until a VNC
              client connects before opening the X display (or -rawfb device).

              This could be useful for delaying opening the display  for  cer-
              tain usage modes (say if x11vnc is started at boot time and no X
              server is running or users logged in yet).

              If the string is, e.g. WAIT:0.0 or WAIT:1, i.e. "WAIT" in  front
              of a normal X display, then that indicated display is used.

              One   can   also   insert   a   geometry  between  colons,  e.g.
              WAIT:1280x1024:... to set the size of the display the VNC client
              first  attaches to since some VNC viewers will not automatically
              adjust to a new framebuffer size.

              A more interesting case is like this:

              WAIT:cmd=/usr/local/bin/find_display

              in which case the command after "cmd="  is  run  to  dynamically
              work  out  the  DISPLAY and optionally the XAUTHORITY data.  The
              first line of the command  output  must  be  of  the  form  DIS-
              PLAY=<xdisplay>.   On Linux if the virtual terminal is known ap-
              pend ",VT=n" to this string and the chvt(1) program will also be
              run.   Any remaining output is taken as XAUTHORITY data.  It can
              be either of the form XAUTHORITY=<file> or raw  xauthority  data
              for the display. For example;

              xauth extract - $DISPLAY"

              NOTE:  As  specified  in  the previous paragraph, you can supply
              your own WAIT:cmd=... program or script, BUT there are two  very
              useful  *BUILT-IN*  ones:  FINDDISPLAY  (alias  -find above) and
              FINDCREATEDISPLAY (alias -create above.)  Most people use  these
              instead of creating their own script.  Read the following (espe-
              cially the BUILT-IN modes sections)  to  see  how  to  configure
              these two useful builtin -display WAIT: modes.

              In  the  case of -unixpw (and -unixpw_nis only if x11vnc is run-
              ning as root), then the cmd= command is run as the user who just
              authenticated via the login and password prompt.

              In the case of -unixpw_cmd, the commands will also be run as the
              logged-in user, as long as the user-supplied helper program sup-
              ports RFB_UNIXPW_CMD_RUN (see the -unixpw_cmd option.)

              Also  in  the  case  of -unixpw, the user logging in can place a
              colon at the end of her  username  and  supply  a  few  options:
              scale=,  scale_cursor=  (or sc=), solid (or so), id=, clear_mods
              (or cm), clear_keys (or ck), clear_all (or ca), repeat,  speeds=
              (or  sp=),  readtimeout=  (or rd=), viewonly (or vo), nodisplay=
              (or nd=), rotate= (or ro=), or noncache (or nc),  all  separated
              by  commas  if  there  is more than one.  After the user logs in
              successfully, these options will be applied to the  VNC  screen.
              For example,

              login: fred:scale=3/4,sc=1,repeat Password: ...

              login: runge:sp=modem,rd=120,solid

              for  convenience  m/n  implies scale= e.g. fred:3/4  If you type
              and enter your password incorrectly, to retrieve your long  "lo-
              gin:"  line  press  the  Up  arrow  once (before typing anything
              else).

              Most of these colon options only apply to the  builtin  FINDDIS-
              PLAY  and FINDCREATEDISPLAY modes, but note that they are passed
              to the extrenal command in the environment as well and so  could
              be used.

              In  the login panel, press F1 to get a list of the available op-
              tions that you can add after the username.

              Another option is "geom=WxH" or "geom=WxHxD" (or ge=). This only
              has  an effect in FINDCREATEDISPLAY mode when a virtual X server
              such as Xvfb is going to be created.   It  sets  the  width  and
              height  of  the  new  display, and optionally the color depth as
              well.

              You can  also  supply  "gnome",  "kde",  "twm",  "fvwm",  "mwm",
              "dtwm",  "wmaker",  "xfce", "lxde", "enlightenment", "Xsession",
              or "failsafe" (same as "xterm") to have the created display  use
              that mode for the user session.

              Specify  "tag=..."  to set the unique FD_TAG desktop session tag
              described below.  Note: this  option  will  be  ignored  if  the
              FD_TAG  env.  var. is already set or if the viewer-side supplied
              value is not completely composed of alphanumeric or '_'  or  '-'
              characters.

              User  preferences  file:  Instead  of  having  the  user type in
              geom=WxH,... etc. every time he logs in to find or create his  X
              session,  if you set FD_USERPREFS to a string that does not con-
              tain the "/"  character,  then  the  user's  home  directory  is
              prepended  to  that string and if the file exists its first line
              is read and appended to any options he supplied  at  the  login:
              prompt.   For  example  -env FD_USERPREFS=.x11vnc_create and the
              user put "geom=1600x1200" in his ~/.x11vnc_create file.

              To disable the  option  setting  set  the  environment  variable
              X11VNC_NO_UNIXPW_OPTS=1  before  starting  x11vnc.   To  set any
              other options, the user can use the gui (x11vnc -gui connect) or
              the  remote  control  method  (x11vnc -R opt:val) during his VNC
              session.

              So we see the combination of -display WAIT:cmd=...  and  -unixpw
              allows  automatic pairing of an unix authenticated VNC user with
              his desktop.  This could be very useful on SunRays and also  any
              system  where  multiple  users  share a given machine.  The user
              does not need to remember special ports or passwords set up  for
              his desktop and VNC.

              A  nice way to use WAIT:cmd=... is out of inetd(8) (it automati-
              cally forks a new x11vnc for  each  user).   You  can  have  the
              x11vnc  inetd spawned process run as, say, root or nobody.  When
              run as root (for either inetd or display manager), you can  also
              supply  the  option  "-users unixpw=" to have the x11vnc process
              switch to the user as well.  Note:  there  will  be  a  2nd  SSL
              helper process that will not switch, but it is only encoding and
              decoding the encrypted stream at that point.

              BUILT-IN modes:

              -- Automatic Finding of User X Sessions --

              As a special case, WAIT:cmd=FINDDISPLAY will run a  script  that
              works  on most Unixes to determine a user's DISPLAY variable and
              xauthority data (see who(1) ).

              NOTE: The option "-find" is an alias for this mode.

              To have this default script printed to  stdout  (e.g.  for  cus-
              tomization)  run  with  WAIT:cmd=FINDDISPLAY-print  To  have the
              script run to print what display it would find use "-finddpy" or
              WAIT:cmd=FINDDISPLAY-run

              The  standard script runs xdpyinfo(1) run on potential displays.
              If your X server(s) have a login greeter that exclusively  grabs
              the Xserver, then xdpyinfo blocks forever and this mode will not
              work.  See www.karlrunge.com/x11vnc/faq.html#faq-display-manager
              for  how to disable this for dtgreet on Solaris and possibly for
              other greeters.

              In -find/cmd=FINDDISPLAY mode, if you set FD_XDM=1, e.g. 'x11vnc
              -env FD_XDM=1 -find ...' and x11vnc is running as root (e.g. in-
              etd) then it will try to find the XAUTHORITY file of  a  running
              XDM/GDM/KDM  login  greeter  (i.e.  no user has logged into an X
              session yet.)

              As another special case, WAIT:cmd=HTTPONCE will allow x11vnc  to
              service one http request and then exit.  This is usually done in
              -inetd mode to run  on,  say,  port  5800  and  allow  the  Java
              vncviewer to be downloaded by client web browsers.  For example:

              5815  stream tcp nowait root /usr/sbin/tcpd /.../x11vnc \ -inetd
              -q -http_ssl -prog /.../x11vnc \ -display WAIT:cmd=HTTPONCE

              Where /.../x11vnc is the full path to x11vnc.  It is used in the
              Apache SSL-portal example (see FAQ).

              In  this  mode  you can set X11VNC_SKIP_DISPLAY to a comma sepa-
              rated list of displays (e.g. ":0,:1") to ignore in  the  finding
              process.  The ":" is optional.  Ranges n-m e.g. 0-20 can also be
              supplied. This string can also be set by the connecting user via
              "nd="  using  "+"  instead  of  ","   If  "nd=all"  or  you  set
              X11VNC_SKIP_DISPLAY=all then all display finding fails as if you
              set X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 (below.)

              On  some  systems  lsof(1)  can be very slow.  Set the env. var.
              FIND_DISPLAY_NO_LSOF=1 to skip using lsof to  try  to  find  the
              Linux   VT   the   X   server  is  running  on.   set  FIND_DIS-
              PLAY_NO_VT_FIND=1 to avoid looking at all.

              -- Automatic Creation of User X Sessions --

              An interesting option is WAIT:cmd=FINDCREATEDISPLAY that is like
              FINDDISPLAY  in that is uses the same method to find an existing
              display.  However, if it does  not  find  one  it  will  try  to
              *start*  up  an X server session for the user.  This is the only
              time x11vnc tries to actually start up an X server.

              NOTE: The option "-create" is an alias for this mode.

              It will start looking for an open display number at :20 Override
              via X11VNC_CREATE_STARTING_DISPLAY_NUMBER=n By default 80 X dis-
              plays are allowed (i.e. going to :99) Override  via  X11VNC_CRE-
              ATE_MAX_DISPLAYS=n

              For  its  heuristics, the create display script sets LC_ALL=C so
              that command output is uniform.  By default it will try  to  re-
              store  LC_ALL  right before starting the user session.  However,
              if you don't  mind  it  keeping  LC_ALL=C  set  the  env.  var.:
              X11VNC_CREATE_LC_ALL_C_OK=1

              By default FINDCREATEDISPLAY will try Xvfb and then Xdummy:

              The   Xdummy   wrapper   is  part  of  the  x11vnc  source  code
              (x11vnc/misc/Xdummy)  It should be available in  PATH  and  have
              run "Xdummy -install" once to create the shared library.  Xdummy
              only works on Linux.  As of 12/2009 it no longer needs to be run
              as root, and the default is to not run as root.  In some circum-
              stances permissions may require running it  as  root,  in  these
              cases  specify FD_XDUMMY_RUN_AS_ROOT=1, this is the same as sup-
              plying -root to the Xdummy cmdline.

              Xvfb is available on most platforms and does not require root.

              An advantage of Xdummy over Xvfb is that Xdummy  supports  RANDR
              dynamic screen resizing.

              When  x11vnc  exits (i.e. user disconnects) the X server session
              stays running in the background.  The FINDDISPLAY will  find  it
              directly  next  time.   The  user must exit the X session in the
              usual way for it to terminate (or kill the X server  process  if
              all else fails).

              To troubleshoot the FINDCREATEDISPLAY mechanism, set the follow-
              ing env. var. to  an  output  log  file,  e.g  -env  CREATE_DIS-
              PLAY_OUTPUT=/tmp/mydebug.txt

              So  this is a somewhat odd mode for x11vnc in that it will start
              up and poll virtual X servers!  This can be used from, say,  in-
              etd(8)  to  provide a means of definitely getting a desktop (ei-
              ther real or virtual) on the machine.  E.g. a desktop service:

              5900 stream tcp nowait root /usr/sbin/tcpd /.../x11vnc -inetd -q
              -http  -ssl  SAVE  -unixpw  -users unixpw=\ -passwd secret -prog
              /.../x11vnc \ -display WAIT:cmd=FINDCREATEDISPLAY

              Where /.../x11vnc is the full path to x11vnc.

              See the -svc/-service option alias above.

              If for some reason you do not want x11vnc to ever try to find an
              existing   display   set  the  env.  var  X11VNC_FINDDISPLAY_AL-
              WAYS_FAILS=1 (also -env  ...)   This  is  the  same  as  setting
              X11VNC_SKIP_DISPLAY=all or supplying "nd=all" after "username:"

              Use  WAIT:cmd=FINDCREATEDISPLAY-print  to  print  out the script
              that is used for this.

              You  can  specify  the  preferred  X  server  order  via   e.g.,
              WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb,X   and/or leave out ones
              you do not want.  The the case "X" means try to start up a real,
              hardware  X server using xinit(1) or startx(1).  If there is al-
              ready an X server running the X case may only work on Linux (see
              startx(1) ).

              "Xvnc"  will  start  up a VNC X server (real- or tight-vnc, e.g.
              use if Xvfb is not available).  "Xsrv" will start up the  server
              program  in  the  variable "FD_XSRV" if it is non-empty. You can
              make this be a wrapper script if you like (it  must  handle  :N,
              -geometry, and -depth and other X server options).

              You  can  set  the  environment variable FD_GEOM (or X11VNC_CRE-
              ATE_GEOM) to WxH or WxHxD to set the width and  height  and  op-
              tionally  the  color depth of the created display.  You can also
              set FD_SESS to be the session (short name of the  windowmanager:
              kde, gnome, twm, failsafe, etc.). FD_OPTS contains extra options
              to pass to the X server. You can also set FD_PROG to be the full
              path to the session/windowmanager program.

              More  FD tricks:  FD_CUPS=port or FD_CUPS=host:port will set the
              cups  printing  environment.   Similarly  for   FD_ESD=port   or
              FD_ESD=host:port  for esddsp sound redirection.  Set FD_EXTRA to
              a command to be run a few seconds after the X server starts  up.
              Set  FD_TAG to be a unique name for the session, it is set as an
              X property, that makes FINDDISPLAY only find sessions with  that
              tag value.

              Set  FD_XDMCP_IF  to the network interface that the display man-
              ager is running on; default is 'localhost' but you may  need  to
              set  it to '::1' on some IPv6 only systems or misconfigured dis-
              play managers.

              If you want the FINDCREATEDISPLAY session to  contact  an  XDMCP
              login  manager  (xdm/gdm/kdm)  on  the  same  machine,  then use
              "Xvfb.xdmcp" instead of "Xvfb", etc.  The user will have to sup-
              ply  his username and password one more time (but he gets to se-
              lect his desktop type so that can be useful).  For this to work,
              you  will  need to enable localhost XDMCP (udp port 177) for the
              display manager.  This seems to be:

              for gdm in gdm.conf:   Enable=true in section [xdmcp] for kdm in
              kdmrc:       Enable=true  in section [Xdmcp] for xdm in xdm-con-
              fig: DisplayManager.requestPort: 177

              See  the  shorthand  options   above   "-svc",   "-xdmsvc"   and
              "-sshxdmsvc"  that  specify  the  above  options for some useful
              cases.

              If you set the env. var WAITBG=1 x11vnc will go into  the  back-
              ground once listening in wait mode.

              Another  special  mode  is  FINDCREATEDISPLAY-Xvnc.redirect, (or
              FINDDISPLAY-Xvnc.redirect).  In this case it will start up  Xvnc
              as above if needed, but instead of polling it in its normal way,
              it simply does a socket redirection of the connected VNC  viewer
              to the Xvnc.

              So  in Xvnc.redirect x11vnc does no VNC but merely transfers the
              data back and  forth.   This  should  be  faster  then  x11vnc's
              polling  method,  but  not as fast as connecting directly to the
              Xvnc with the VNC Viewer.  The idea here is to take advantage of
              x11vnc's display finding/creating scheme, SSL, and perhaps a few
              others.  Most of x11vnc's options do not apply in this mode.

              Xvnc.redirect should also work for the vnc.so  X  server  module
              for  the  h/w  display however it will work only for finding the
              display and the user must already be logged into the X console.

       -vencrypt mode

              The VeNCrypt extension to  the  VNC  protocol  allows  encrypted
              SSL/TLS connections.  If the -ssl mode is enabled, then VeNCrypt
              is enabled as well BY DEFAULT (they both use a  SSL/TLS  tunnel,
              only the protocol handshake is a little different.)

              To  control  when  and  how  VeNCrypt  is used, specify the mode
              string.  If mode is "never", then VeNCrypt is not used.  If mode
              is  "support" (the default) then VeNCrypt is supported.  If mode
              is "only", then the similar and older ANONTLS  protocol  is  not
              simultaneously  supported.   x11vnc's  normal SSL mode (vncs://)
              will be supported under -ssl unless you set mode to "force".

              If mode is prefixed with "nodh:", then Diffie Hellman  anonymous
              key  exchange  is disabled.  If mode is prefixed with "nox509:",
              then X509 key exchange is disabled.

              To disable all Anonymous Diffie-Hellman access  (susceptible  to
              Man-In-The-Middle  attack)  you  will  need to supply "-vencrypt
              nodh:support -anontls never" or "-vencrypt nodh:only"

              If mode is prefixed with "newdh:", then new Diffie  Hellman  pa-
              rameters  are  generated  for  each connection (this can be time
              consuming: 1-60 secs; see -dhparams  below  for  a  faster  way)
              rather than using the fixed values in the program.  Using fixed,
              publicly known values is not known to  be  a  security  problem.
              This setting applies to ANONTLS as well.

              Long example: -vencrypt newdh:nox509:support

              Also, if mode is prefixed with "plain:", then if -unixpw mode is
              active the VeNCrypt "*Plain" username+passwd method  is  enabled
              for  Unix  logins.   Otherwise  in -unixpw mode the normal login
              panel is provided.

              You *MUST* supply the -ssl option for  VeNCrypt  to  be  active.
              The -vencrypt option only fine-tunes its operation.

       -anontls mode

              The  ANONTLS  extension  to  the  VNC  protocol allows encrypted
              SSL/TLS connections.  If the -ssl mode is enabled, then  ANONTLS
              is  enabled  as well BY DEFAULT (they both use a SSL/TLS tunnel,
              only the protocol handshake is a little different.)

              ANONTLS is an older SSL/TLS mode introduced by vino.

              It is referred to as 'TLS' for its registered VNC  security-type
              name,  but we use the more descriptive 'ANONTLS' here because it
              provides only Anonymous  Diffie-Hellman  encrypted  connections,
              and hence no possibility for certificate authentication.

              To  control  when  and  how  ANONTLS  is  used, specify the mode
              string.  If mode is "never", then ANONTLS is not used.  If  mode
              is  "support"  (the default) then ANONTLS is supported.  If mode
              is "only", then the similar VeNCrypt protocol is not  simultane-
              ously  supported.   x11vnc's  normal  SSL mode (vncs://) will be
              supported under -ssl unless you set mode to "force".

              If mode is prefixed with "newdh:", then new Diffie  Hellman  pa-
              rameters  are  generated  for  each connection (this can be time
              consuming: 1-60 secs; see -dhparams  below  for  a  faster  way)
              rather than using the fixed values in the program.  Using fixed,
              publicly known values is not known to  be  a  security  problem.
              This  setting  applies to VeNCrypt as well.  See the description
              of "plain:" under -vencrypt.

              Long example: -anontls newdh:plain:support

              You *MUST* supply the -ssl option for ANONTLS to be active.  The
              -anontls option only fine-tunes its operation.

       -sslonly

              Same  as: "-vencrypt never -anontls never"  i.e. it disables the
              VeNCrypt and ANONTLS encryption methods and only allows standard
              SSL  tunneling.   You  must also supply the -ssl ... option (see
              below.)

       -dhparams file

              For some operations a set of Diffie  Hellman  parameters  (prime
              and generator) is needed.  If so, use the parameters in file. In
              particular, the VeNCrypt and  ANONTLS  anonymous  DH  mode  need
              them.   By default a fixed set is used. If you do not want to do
              that you can specify "newdh:" to the -vencrypt and -anontls  op-
              tions  to  generate a new set each session.  If that is too slow
              for you, use -dhparams file to a set you  created  manually  via
              "openssl dhparam -out file 1024"

       -nossl

              Disable  the  -ssl  option (see below). Since -ssl is off by de-
              fault -nossl would only be used on the commandline to unset  any
              *earlier* -ssl option (or -svc...)

       -ssl [pem]

              Use  the openssl library (www.openssl.org) to provide a built-in
              encrypted SSL/TLS tunnel between VNC viewers and  x11vnc.   This
              requires  libssl  support  to  be  compiled into x11vnc at build
              time.  If x11vnc is not built with libssl support it  will  exit
              immediately  when  -ssl  is prescribed.  See the -stunnel option
              below for an alternative.

              The VNC Viewer-side needs to support SSL/TLS as well.  See  this
              URL and also the discussion below for ideas on how to enable SSL
              support       for       the       viewer:       http://www.karl-
              runge.com/x11vnc/faq.html#faq-ssl-tun nel-viewers .  x11vnc pro-
              vides an SSL enabled Java viewer applet in the  classes/ssl  di-
              rectory  (-http  or -httpdir options.)  The SSVNC viewer package
              supports SSL tunnels too.

              If the VNC Viewer supports VeNCrypt or ANONTLS  (vino's  encryp-
              tion  mode)  they  are  also supported by the -ssl mode (see the
              -vencrypt and -anontls options for more info;  use  -sslonly  to
              disable both of them.)

              Use  "-ssl  /path/to/mycert.pem"  to  specify an SSL certificate
              file in PEM format to use to identify and provide a key for this
              server.   See  openssl(1)  for  more  info  about  PEMs  and the
              -sslGenCert and "-ssl SAVE" options  below  for  how  to  create
              them.

              The connecting VNC viewer SSL tunnel can (at its option) authen-
              ticate this server if it has the public key part of the certifi-
              cate (or a common certificate authority, CA, is a more sophisti-
              cated way to verify this server's cert,  see  -sslGenCA  below).
              This  authentication  is  done  to prevent Man-In-The-Middle at-
              tacks.   Otherwise,  if  the  VNC  viewer  simply  accepts  this
              server's key WITHOUT verification, the traffic is protected from
              passive sniffing on the network, but *NOT* from  Man-In-The-Mid-
              dle attacks. There are hacker tools like dsniff/webmitm and cain
              that implement SSL Man-In-The-Middle attacks.

              If [pem] is empty or the string "SAVE" then the openssl(1)  com-
              mand  must  be  available  to generate the certificate the first
              time.  A self-signed certificate is generated (see -sslGenCA and
              -sslGenCert  for  use  of  a Certificate Authority.)  It will be
              saved to the file ~/.vnc/certs/server.pem.  On subsequent  calls
              if that file already exists it will be used directly.

              Use  "SAVE_NOPROMPT" to avoid being prompted to protect the gen-
              erated key with a passphrase.  However in -inetd and  -bg  modes
              there will be no prompting for a passphrase in either case.

              If  [pem]  is  "SAVE_PROMPT"  the server.pem certificate will be
              created based on your answers to its prompts for all  info  such
              as OrganizationalName, CommonName, etc.

              Use  "SAVE-<string>"  and "SAVE_PROMPT-<string>" to refer to the
              file ~/.vnc/certs/server-<string>.pem instead (it will be gener-
              ated  if  it  does not already exist).  E.g. "SAVE-charlie" will
              store to the file ~/.vnc/certs/server-charlie.pem

              Examples: x11vnc -ssl SAVE -display :0 ...   x11vnc  -ssl  SAVE-
              someother -display :0 ...

              If  [pem]  is "TMP" and the openssl(1) utility command exists in
              PATH, then a temporary, self-signed certificate will  be  gener-
              ated for this session.  If openssl(1) cannot be used to generate
              a temporary certificate x11vnc exits immediately.  The temporary
              cert will be discarded when x11vnc exits.

              If  successful  in using openssl(1) to generate a temporary cer-
              tificate in "SAVE" or "TMP" creation modes, the public  part  of
              it  will  be  displayed to stderr (e.g. one could copy it to the
              client-side to provide authentication of the server to VNC view-
              ers.)

              NOTE:  In  "TMP" mode, unless you safely copy the public part of
              the temporary Cert to the viewer for authenticate  *every  time*
              (unlikely...),  then only passive sniffing attacks are prevented
              and you are still open to Man-In-The-Middle  attacks.   This  is
              why the default "SAVE" mode is preferred (and more sophisticated
              CA mode too).  Only with saved keys AND the VNC viewer authenti-
              cating  them (via the public certificate), are Man-In-The-Middle
              attacks prevented.

              If [pem] is "ANON" then the  Diffie-Hellman  anonymous  key  ex-
              change method is used.  In this mode there are *no* SSL certifi-
              cates and so it is not possible to authenticate either  the  VNC
              server  or  VNC  client.  Thus only passive network sniffing at-
              tacks are avoided: the "ANON" method is susceptible  to  Man-In-
              The-Middle  attacks.   "ANON"  is not recommended; instead use a
              SSL PEM you created or the default "SAVE" method.

              See -ssldir  below  to  use  a  directory  besides  the  default
              ~/.vnc/certs

              If your x11vnc binary was not compiled with OpenSSL library sup-
              port, use of the -ssl option will induce  an  immediate  failure
              and exit.  For such binaries, consider using the -stunnel option
              for SSL encrypted connections.

              Misc Info: In temporary cert creation mode "TMP", set  the  env.
              var.  X11VNC_SHOW_TMP_PEM=1  to have x11vnc print out the entire
              certificate, including the PRIVATE KEY part, to  stderr.   There
              are  better  ways  to  get/save this info.  See "SAVE" above and
              "-sslGenCert" below.

       -ssltimeout n

              Set SSL read timeout to n seconds.  In some situations (i.e.  an
              iconified  viewer  in  Windows) the viewer stops talking and the
              connection is dropped after the default timeout (25s  for  about
              the  first  minute, 43200s later).  Set to zero to poll forever.
              Set to a negative value to use the builtin setting.

              Note that this value does NOT apply to the  *initial*  ssl  init
              connection.   The  default  timeout for that is 20sec.  Use -env
              SSL_INIT_TIMEOUT=n to modify it.

       -sslnofail

              Exit at the first SSL connection failure. Useful when  scripting
              SSL  connections (e.g. x11vnc is started via ssh) and you do not
              want x11vnc waiting around for more connections, tying up ports,
              etc.

       -ssldir dir

              Use  dir  as  an  alternate  ssl  certificate and key management
              toplevel directory.  The default is ~/.vnc/certs

              This directory is used to store server  and  other  certificates
              and  keys  and also other materials.  E.g. in the simplest case,
              "-ssl SAVE" will store the x11vnc server cert in dir/server.pem

              Use of alternate directories via -ssldir allows  you  to  manage
              multiple VNC Certificate Authority (CA) keys.  Another use is if
              ~/.vnc/cert is on an NFS share you might want your  certificates
              and keys to be on a local filesystem to prevent network snooping
              (for example -ssldir /var/lib/x11vnc-certs).

              -ssldir affects nearly all of the other -ssl* options, e.g. -ssl
              SAVE, -sslGenCert, etc..

       -sslverify path

              For  either  of  the -ssl or -stunnel modes, use path to provide
              certificates to authenticate incoming VNC  *Client*  connections
              (normally only the server is authenticated in SSL.)  This can be
              used as a method to replace standard password authentication  of
              clients.

              If  path  is a directory it contains the client (or CA) certifi-
              cates in separate files.  If path is a file, it contains one  or
              more  certificates.  See special tokens below.  These correspond
              to the "CApath = dir" and "CAfile = file" stunnel options.   See
              the stunnel(8) manpage for details.

              Examples: x11vnc -ssl -sslverify ~/my.crt x11vnc -ssl -sslverify
              ~/my_pem_dir/

              Note that if path is a directory, it must contain the  certs  in
              separate files named like <HASH>.0, where the value of <HASH> is
              found by running the command  "openssl  x509  -hash  -noout  -in
              file.crt".  Evidently  one  uses  <HASH>.1  if there is a colli-
              sion...

              The  the  key-management  utility  "-sslCertInfo   HASHON"   and
              "-sslCertInfo  HASHOFF"  will create/delete these hashes for you
              automatically (via symlink) in  the  HASH  subdirs  it  manages.
              Then you can point -sslverify to the HASH subdir.

              Special  tokens: in -ssl mode, if path is not a file or a direc-
              tory, it is taken as a comma separated list of tokens  that  are
              interpreted as follows:

              If  a  token is "CA" that means load the CA/cacert.pem file from
              the ssl directory.  If a token is "clients" then all  the  files
              clients/*.crt  in  the  ssl directory are loaded.  Otherwise the
              file clients/token.crt is attempted to be loaded.  As a  kludge,
              use a token like ../server-foo to load a server cert if you find
              that necessary.

              Use -ssldir to use a directory different from  the  ~/.vnc/certs
              default.

              Note that if the "CA" cert is loaded you do not need to load any
              of the certs that have been signed by it.  You will need to load
              any additional self-signed certs however.

              Examples:  x11vnc  -ssl  -sslverify  CA  x11vnc  -ssl -sslverify
              self:fred,self:jim x11vnc -ssl -sslverify CA,clients

              Usually  "-sslverify  CA"  is  the  most  effective.   See   the
              -sslGenCA  and  -sslGenCert  options below for how to set up and
              manage the CA framework.

              NOTE: the  following  utilities,  -sslGenCA,  -sslGenCert,  -ss-
              lEncKey,  -sslCertInfo,  and  -sslCRL are provided for complete-
              ness, but for casual usage they are overkill.

              They provide VNC Certificate Authority  (CA)  key  creation  and
              server  /  client key generation and signing.  So they provide a
              basic Public Key management framework for VNC-ing  with  x11vnc.
              (note that they require openssl(1) be installed on the system)

              However, the simplest usage mode, "-ssl TMP" (where x11vnc auto-
              matically generates its own, self-signed, temporary key and  the
              VNC  viewers  always accept it, e.g. accepting via a dialog box)
              is probably safe enough for most scenarios.   CA  management  is
              not needed.

              To  protect against Man-In-The-Middle attacks the "TMP" mode can
              be improved by using "-ssl SAVE" (same as "-ssl", i.e.  the  de-
              fault)  to have x11vnc create a longer term self-signed certifi-
              cate, and then (safely) copy the corresponding public  key  cert
              to  the  desired client machines (care must be taken the private
              key part is not stolen; you will be prompted for a passphrase).

              So keep in mind no CA key creation or management (-sslGenCA  and
              -sslGenCert)  is needed for either of the above two common usage
              modes.

              One might want to use -sslGenCA and -sslGenCert  if  you  had  a
              large  number  of  VNC client and server workstations.  That way
              the administrator could generate a single CA key with  -sslGenCA
              and distribute its certificate part to all of the workstations.

              Next, he could create signed VNC server keys (-sslGenCert server
              ...) for each workstation or user that then x11vnc would use  to
              authenticate itself to any VNC client that has the CA cert.

              Optionally,  the  admin  could  also  make it so the VNC clients
              themselves are authenticated to x11vnc (-sslGenCert client  ...)
              For  this  -sslverify  would  be  pointed to the CA cert (and/or
              self-signed certs).

              x11vnc will be able to use all of these cert and key files.   On
              the  VNC  client  side, they will need to be "imported" somehow.
              Web browsers have "Manage Certificates" actions as does the Java
              applet  plugin  Control Panel.  stunnel can also use these files
              (see the ss_vncviewer example script in the FAQ and SSVNC.)

       -sslCRL path

              Set the Certificate Revocation Lists (CRL) to path.   This  set-
              ting applies for both -ssl and -stunnel modes.

              If  path  is  a  file, the file contains one or more CRLs in PEM
              format.  If path is a directory, it contains hash named files of
              CRLs  in  the  usual  OpenSSL manner.  See the OpenSSL and stun-
              nel(8) documentation for more info.

              This option only applies if -sslverify  has  been  supplied:  it
              checks for revocation along the certificate chain used to verify
              the VNC client.  The -sslCRL setting will be ignored  when  -ss-
              lverify is not specified.

              Note that if a CRL's expiration date has passed, all SSL connec-
              tions will fail regardless of if they are related to the subject
              of the CRL or not.

              Only  rarely  will  one's x11vnc -ssl infrastructure be so large
              that this option would be useful (since normally maintaining the
              contents  of the -sslverify file or directory should be enough.)
              However, when using x11vnc with  a  Certificate  Authority  (see
              -sslGenCA)  to authenticate Clients via SSL/TLS, the -sslCRL op-
              tion can be useful to revoke users' certs whose private SSL keys
              were  lost  or stolen (e.g. laptop.)  This way a new CA cert+key
              does not need to be created and new signed client keys generated
              and distributed to all users.

              To  create  a  CRL  file  with revoked certificates the commands
              'openssl ca -revoke ...' and 'openssl ca -gencrl ...'  are  use-
              ful.  (Run them in ~/.vnc/certs)

       -sslGenCA [dir]

              Generate  your  own  Certificate Authority private key, certifi-
              cate, and other files in directory [dir].  x11vnc then exits.

              If [dir] is not supplied, a -ssldir setting is used,  or  other-
              wise ~/.vnc/certs is used.

              This  command  also  creates directories where server and client
              certs and keys will be stored.  The openssl(1) program  must  be
              installed on the system and available in PATH.

              After  the  CA files and directories are created the x11vnc com-
              mand exits; the VNC server is not run.

              You will be prompted for information to put into the CA certifi-
              cate.   The  info  does  not have to be accurate just as long as
              clients accept the cert for VNC connections.  You will also need
              to  supply a passphrase of at least 4 characters for the CA pri-
              vate key.

              Once you have generated the CA you can distribute  its  certifi-
              cate  part, [dir]/CA/cacert.pem, to other workstations where VNC
              viewers will be run.  One will need to "import" this certificate
              in the applications, e.g. Web browser, Java applet plugin, stun-
              nel, etc.  Next, you can create and sign keys using the CA  with
              the -sslGenCert option below.

              Examples:  x11vnc  -sslGenCA  x11vnc -sslGenCA  ~/myCAdir x11vnc
              -ssldir ~/myCAdir -sslGenCA

              (the last two lines are equivalent)

       -sslGenCert type name

              Generate a VNC server or client certificate and private key pair
              signed  by  the  CA  created  previously  with  -sslGenCA.   The
              openssl(1) program must be installed on the system and available
              in PATH.

              After  the Certificate is generated x11vnc exits; the VNC server
              is not run.

              The type of key to be generated is the string type.  It  is  ei-
              ther  "server"  (i.e.  for use by x11vnc) or "client" (for a VNC
              viewer).  Note that typically only "server"  is  used:  the  VNC
              clients authenticate themselves by a non-public-key method (e.g.
              VNC or unix password).  type is required.

              An arbitrary default name you want to associate with the key  is
              supplied  by  the name string.  You can change it at the various
              prompts when creating the key.  name is optional.

              If name is left blank for clients keys then  "nobody"  is  used.
              If  left  blank  for  server  keys, then the primary server key:
              "server.pem" is created (this is the  saved  one  referenced  by
              "-ssl SAVE" when the server is started)

              If  name  begins with the string "self:" then a self-signed cer-
              tificate is created instead of one signed by your CA key.

              If name begins with the string "req:" then only a key (.key) and
              a  certificate  signing *request* (.req) are generated.  You can
              then send the .req file to an external CA (even  a  professional
              one,  e.g.  Thawte)  and  then combine the .key and the received
              cert into the .pem file with the same basename.

              The distinction between "server"  and  "client"  is  simply  the
              choice  of output filenames and sub-directory.  This makes it so
              the -ssl SAVE-name option can easily pick up the x11vnc PEM file
              this option generates.  And similarly makes it easy for the -ss-
              lverify option to pick up your client certs.

              There is nothing special about the filename or  directory  loca-
              tion  of either the "server" and "client" certs.  You can rename
              the files or move them to wherever you like.

              Precede this option with -ssldir [dir] to use a directory  other
              than  the default ~/.vnc/certs You will need to run -sslGenCA on
              that directory first before doing any -sslGenCert key creation.

              Note you cannot recreate a cert with exactly the  same  distigu-
              ished  name (DN) as an existing one.  To do so, you will need to
              edit the [dir]/CA/index.txt file to delete the line.

              Similar to -sslGenCA, you will be prompted to fill in  some  in-
              formation  that  will  be recorded in the certificate when it is
              created.

              Tip: if you know the fully-qualified hostname other people  will
              be  connecting  to,  you  can use that as the CommonName "CN" to
              avoid some applications (e.g. web browsers and java plugin) com-
              plaining that it does not match the hostname.

              You  will  also  need to supply the CA private key passphrase to
              unlock the private key created from -sslGenCA.  This private key
              is used to sign the server or client certificate.

              The "server" certs can be used by x11vnc directly by pointing to
              them via the -ssl  [pem]  option.   The  default  file  will  be
              ~/.vnc/certs/server.pem.   This one would be used by simply typ-
              ing -ssl SAVE.  The pem file contains both the  certificate  and
              the private key.  server.crt file contains the cert only.

              The  "client" cert + private key file will need to be copied and
              imported into the VNC viewer  side  applications  (Web  browser,
              Java  plugin,  stunnel,  etc.)  Once that is done you can delete
              the "client" private key file on this machine since it  is  only
              needed     on     the    VNC    viewer    side.     The,    e.g.
              ~/.vnc/certs/clients/<name>.pem contains both the cert and  pri-
              vate key.  The <name>.crt contains the certificate only.

              NOTE:  It is very important to know one should generate new keys
              with a passphrase.  Otherwise if an untrusted  user  steals  the
              key  file he could use it to masquerade as the x11vnc server (or
              VNC viewer client).  You will be prompted whether to encrypt the
              key  with  a  passphrase or not.  It is recommended that you do.
              One inconvenience to a passphrase is that it must  be  typed  in
              EVERY time x11vnc or the client app is started up.

              Examples:

              x11vnc -sslGenCert server x11vnc -ssl SAVE -display :0 ...

              and  then  on viewer using ss_vncviewer stunnel wrapper (see the
              FAQ): ss_vncviewer -verify ./cacert.crt hostname:0

              (this assumes the cacert.crt  cert  from  -sslGenCA  was  safely
              copied to the VNC viewer machine where ss_vncviewer is run)

              Example using a name:

              x11vnc -sslGenCert server charlie x11vnc -ssl SAVE-charlie -dis-
              play :0 ...

              Example for a client certificate (rarely used):

              x11vnc        -sslGenCert        client        roger         scp
              ~/.vnc/certs/clients/roger.pem           somehost:.           rm
              ~/.vnc/certs/clients/roger.pem

              x11vnc   is   then   started   with   the   option    -sslverify
              ~/.vnc/certs/clients/roger.crt (or simply -sslverify roger), and
              on the viewer user on somehost could do for example:

              ss_vncviewer -mycert ./roger.pem hostname:0

              If you set the env. var REQ_ARGS='...'  it  will  be  passed  to
              openssl  req(1).  A common use would be REQ_ARGS='-days 1095' to
              bump up the expiration date (3 years in this case).

       -sslEncKey pem

              Utility to encrypt an existing PEM file with  a  passphrase  you
              supply  when prompted.  For that key to be used (e.g. by x11vnc)
              the passphrase must be supplied each time.

              The "SAVE" notation described under -ssl applies as well.  (pre-
              cede this option with -ssldir [dir] to refer a directory besides
              the default ~/.vnc/certs)

              The openssl(1) program must  be  installed  on  the  system  and
              available  in  PATH.  After the Key file is encrypted the x11vnc
              command exits; the VNC server is not run.

              Examples: x11vnc -sslEncKey /path/to/foo.pem  x11vnc  -sslEncKey
              SAVE x11vnc -sslEncKey SAVE-charlie

       -sslCertInfo pem

              Prints  out information about an existing PEM file.  In addition
              the public certificate is also printed.  The openssl(1)  program
              must  be  in PATH. Basically the command "openssl x509 -text" is
              run on the pem.

              After the info is printed the  x11vnc  command  exits;  the  VNC
              server is not run.

              The "SAVE" notation described under -ssl applies as well.

              Using   "LIST"  will  give a list of all certs being managed (in
              the ~/.vnc/certs dir, use -ssldir  to  refer  to  another  dir).
              "ALL" will print out the info for every managed key (this can be
              very long).  Giving a client or server cert shortname will  also
              try  a  lookup (e.g. -sslCertInfo charlie).  Use "LISTL" or "LL"
              for a long (ls -l style) listing.

              Using "HASHON" will create  subdirs  [dir]/HASH  and  [dir]/HASH
              with  OpenSSL hash filenames (e.g. 0d5fbbf1.0) symlinks pointing
              up to the corresponding *.crt file.  ([dir] is  ~/.vnc/certs  or
              one  given  by -ssldir.)  This is a useful way for other OpenSSL
              applications (e.g. stunnel) to access all of the  certs  without
              having to concatenate them.  x11vnc will not use them unless you
              specifically reference them.  "HASHOFF" removes these HASH  sub-
              dirs.

              The LIST, LISTL, LL, ALL, HASHON, HASHOFF words can also be low-
              ercase, e.g. "list".

       -sslDelCert pem

              Prompts you to delete all .crt .pem .key .req  files  associated
              with  [pem].   x11vnc  then  exits.  "SAVE"  and  lookups  as in
              -sslCertInfo apply as well.

       -sslScripts

              Prints out both the 'genCA' and 'genCert' x11vnc openssl wrapper
              scripts  for  you  to  examine,  modify,  etc.   The scripts are
              printed to stdout and then the x11vnc program exits.

       -stunnel [pem]

              Use the stunnel(8) (stunnel.mirt.net) to  provide  an  encrypted
              SSL tunnel between viewers and x11vnc.

              This  external  tunnel method was implemented prior to the inte-
              grated -ssl encryption described above.  It still works well and
              avoids  the  requirement  of linking with the OpenSSL libraries.
              This mode requires stunnel to be installed  on  the  system  and
              available  via PATH (n.b. stunnel is often installed in sbin di-
              rectories).  Version 4.x of stunnel is assumed (but  see  -stun-
              nel3 below.)

              [pem]  is optional, use "-stunnel /path/to/stunnel.pem" to spec-
              ify a PEM certificate file to pass to stunnel.  See the -ssl op-
              tion for more info on certificate files.

              Whether  or  not your stunnel has its own certificate depends on
              your stunnel configuration; stunnel often generates one  at  in-
              stall time.  See your stunnel documentation for details.  In any
              event, if you want to use this certificate you must  supply  the
              full  path  to it as [pem].  Note: the file may only be readable
              by root.

              [pem] may  also  be  the  special  strings  "TMP",  "SAVE",  and
              "SAVE..." as described in the -ssl option.  If [pem] is not sup-
              plied, "SAVE" is assumed.

              Note that the VeNCrypt, ANONTLS, and "ANON" modes are  not  sup-
              ported in -stunnel mode.

              stunnel  is  started up as a child process of x11vnc and any SSL
              connections stunnel receives are decrypted and  sent  to  x11vnc
              over  a  local socket.  The strings "The SSL VNC desktop is ..."
              and "SSLPORT=..."  are printed out at startup to indicate this.

              The -localhost option is enforced by  default  to  avoid  people
              routing around the SSL channel.  Use -env STUNNEL_DISABLE_LOCAL-
              HOST=1 to disable this security requirement.

              Set -env STUNNEL_DEBUG=1 for more debugging printout.

              Set -env STUNNEL_PROG=xxx to the full path  of  stunnel  program
              you want to be used (e.g. /usr/bin/stunnel4).

              Set -env STUNNEL_LISTEN=xxx to the address of the network inter-
              face to listen on (the default is to listen on all  interfaces),
              e.g. STUNNEL_LISTEN=192.168.1.100.

              A simple way to add IPv6 support is STUNNEL_LISTEN=::

              Your  VNC  viewer  will also need to be able to connect via SSL.
              Unfortunately not too many do this.  See the  information  about
              SSL  viewers  under the -ssl option.  The x11vnc project's SSVNC
              is an option.

              Also, in the x11vnc distribution, patched TightVNC and  UltraVNC
              Java  applet jar files are provided in the classes/ssl directory
              that do SSL connections.  Enable serving them  with  the  -http,
              -http_ssl,  or  -httpdir  (see  the option descriptions for more
              info.)

              Note that for the Java viewer applet usage the  "?PORT=xxxx"  in
              the  various URLs printed at startup will need to be supplied to
              the web browser to connect properly.

              Currently the automatic "single port" HTTPS mode of -ssl is  not
              fully  supported  in -stunnel mode.  However, it can be emulated
              via:

              % x11vnc -stunnel -http_ssl -http_oneport ...

              In general, it is also not too difficult to set up an stunnel or
              other  SSL  tunnel on the viewer side.  A simple example on Unix
              using stunnel 3.x is:

              % stunnel -c -d localhost:5901 -r  remotehost:5900  %  vncviewer
              localhost:1

              For  Windows, stunnel has been ported to it and there are proba-
              bly other such tools available.  See the FAQ and SSVNC for  more
              examples.

       -stunnel3 [pem]

              Use  version  3.x stunnel command line syntax instead of version
              4.x.  The -http/-httpdir Java applet serving  is  currently  not
              available in this mode.

       -enc cipher:keyfile

              Use  symmetric  encryption  with  cipher "cipher" and secret key
              data in "keyfile".  If keyfile is pw=<string> then  "string"  is
              used as the key data.

              NOTE: It is recommended that you use SSL via the -ssl option in-
              stead of this option because SSL is well  understood  and  takes
              great care to establish unique session keys and is more compati-
              ble with other software.  Use this option if you do not want  to
              deal with SSL certificates for authentication and do not want to
              use SSH but want some encryption for your VNC  session.   Or  if
              you  must  interface with a symmetric key tunnel that you do not
              have control over.

              Note that this mode will NOT work with the UltraVNC DSM  plugins
              because  they  alter  the RFB protocol in addition to tunnelling
              with the symmetric cipher (an unfortunate choice of  implementa-
              tion...)

              cipher  can  be one of:  arc4, aesv2, aes-cfb, blowfish, aes256,
              or 3des.  See the OpenSSL documentation for more info.  The key-
              size is 128 bits (except for aes256).  Here is one way to make a
              keyfile with that many bits:

              dd if=/dev/random of=./my.key bs=16 count=1

              you will need to securely share this key with the other side  of
              the VNC connection (See SSVNC for examples).

              Example:     -enc   blowfish:./my.key   Example:    -enc   blow-
              fish:pw=swordfish

              By default 16 bytes of random salt followed by 16 bytes of  ran-
              dom  initialization vector are sent at the very beginning of the
              stream.  The other side must read these and initialize their ci-
              pher with them.  These values make the session key unique (with-
              out them the security is minimal).  Similarly,  the  other  side
              must send us its random salt and IV with those same lengths.

              The salt and key data are combined to create a session key using
              an md5 hash as described in EVP_BytesToKey(3).

              The exact call is: EVP_BytesToKey(Cipher, EVP_md5(), salt,  key-
              data,  len,  1, keystr, NULL);  where salt is the random data as
              described above, and keydata is  the  shared  secret  key  data.
              keystr  is the resulting session key.  The cipher is then seeded
              with keystr and uses the random  initialization  vector  as  its
              first block.

              To  modify  the  amount of random salt and initialization vector
              use cipher@n,m where n is the salt length and m the  initializa-
              tion vector length.  E.g.

              -enc aes-cfb@8,16:./my.key

              It  is  not  a good idea to set either one to zero, although you
              may be forced to if the other side of the tunnel  is  not  under
              your control.

              To  skip the salt and EVP_BytesToKey MD5 entirely (no hashing is
              done: the keydata is directly inserted into the cipher)  specify
              "-1" for the salt, e.g.

              -enc blowfish@-1,16:./my.key

              The  message digest can also be changed to something besides the
              default MD5.  Use cipher@md+n,m where "md" can be  one  of  sha,
              sha1, md5, or ripe.  For example:

              -enc arc4@sha+8,16:./my.key

              The  SSVNC  vnc  viewer  project supplies a symmetric encryption
              tool named "ultravnc_dsm_helper" that can be used on the  viewer
              side.  For example:

              ssvncviewer exec='ultravnc_dsm_helper arc4 my.key 0 h:p'

              where h:p is the hostname and port of the x11vnc server.  ultra-
              vnc_dsm_helper may also be used standalone to provide a  symmet-
              ric  encryption  tunnel  for any viewer or server (VNC or other-
              wise.) The cipher (1st arg) is basically the same syntax  as  we
              use above.

              Also  see the 'Non-Ultra DSM' SSVNC option for the 'UltraVNC DSM
              Encryption Plugin' advanced option.

              For both ways of using the viewer, you can specify the salt,ivec
              sizes (in GUI or, e.g. arc4@8,16).

       -https [port]

              Use  a  special,  separate  HTTPS  port (-ssl and -stunnel modes
              only) for HTTPS Java viewer applet downloading.  I.e.  not  5900
              and not 5800 (the defaults.)

              BACKGROUND:  In  -ssl  mode, it turns out you can use the single
              VNC port (e.g. 5900) for both VNC and HTTPS connections.  (HTTPS
              is  used  to  retrieve  a SSL-aware VncViewer.jar applet that is
              provided with x11vnc).  Since both use  SSL  the  implementation
              was  extended  to  detect  if  HTTP traffic (i.e. GET) is taking
              place and handle it accordingly.  The URL would be, e.g.:

              https://mymachine.org:5900/

              This is convenient for firewalls, etc,  because  only  one  port
              needs to be allowed in.  However, this heuristic adds a few sec-
              onds delay to each connection and can be unreliable  (especially
              if the user takes much time to ponder the Certificate dialogs in
              his browser, Java VM, or VNC Viewer applet.  That's right 3 sep-
              arate "Are you sure you want to connect?" dialogs!)

              END OF BACKGROUND.

              USAGE:  So use the -https option to provide a separate, more re-
              liable HTTPS port that x11vnc will listen on.  If [port] is  not
              provided  (or  is  0),  one  is autoselected.  The URL to use is
              printed out at startup.

              The SSL Java applet directory is specified via the -httpdir  op-
              tion.   If  not supplied, -https will try to guess the directory
              as though the -http option was supplied.

       -httpsredir [port]

              In -ssl mode with the Java applet retrieved via HTTPS, when  the
              HTML   file   containing   applet   parameters  ('index.vnc'  or
              'proxy.vnc') is sent do NOT set the applet PORT parameter to the
              actual  VNC port but set it to "port" instead.  If "port" is not
              supplied, then the port number is guessed from  the  Host:  HTTP
              header.

              This  is  useful  when an incoming TCP connection redirection is
              performed by a router/gateway/firewall from one port to  an  in-
              ternal  machine  where  x11vnc is listening on a different port.
              The Java applet needs to connect to  the  firewall/router  port,
              not  the  VNC port on the internal workstation. For example, one
              could redir from mygateway.com:443 to workstation:5900.

              This spares the user from  having  to  type  in  https://mygate-
              way.com/?PORT=443  into their web browser. Note that port 443 is
              the default https port; other ports  must  be  explicitly  indi-
              cated,  for  example: https://mygateway.com:8000/?PORT=8000.  To
              avoid having to include the PORT= in  the  browser  URL,  simply
              supply "-httpsredir" to x11vnc.

              This option does not work in -stunnel mode.

              More tricks: set the env var X11VNC_EXTRA_HTTPS_PARAMS to be ex-
              tra URL parameters to use.  This way you do not need to  specify
              extra PARAMS in the index.vnc file.  E.g. x11vnc -env X11VNC_EX-
              TRA_HTTPS_PARAMS='?GET=1' ...

              If you do not want to expose the non-SSL HTTP port to  the  net-
              work  (i.e.  you just want the single VNC/HTTPS port, e.g. 5900,
              open   for   connections)   then   specify   the   option   -env
              X11VNC_HTTP_LISTEN_LOCALHOST=1   This  way the connection to the
              LibVNCServer httpd server will only be  available  on  localhost
              (note  that in -ssl mode, HTTPS requests are redirected from SSL
              to the non-SSL LibVNCServer HTTP server.)

       -http_oneport

              For UN-encrypted connections mode (i.e. no  -ssl,  -stunnel,  or
              -enc options), allow the Java VNC Viewer applet to be downloaded
              thru the VNC port via HTTP.

              That is to say, you can use a single port for Java applet viewer
              connections  by  using  a URL in your web browser like this, for
              example:

              http://hostname:5900

              The regular, two-port mode, URL http://hostname:5800  will  con-
              tinue to work as well.

              As  mentioned  above,  this  mode  will  NOT work with the -ssl,
              -stunnel, or -enc encryption options.  Note that is  it  equiva-
              lent  to  '-enc none' (i.e. it uses the same detection mechanism
              as for HTTPS, but with no encryption.)

              HTTPS single-port is on by default in -ssl encrypted  mode  (and
              -enc too), so you only need -http_oneport when doing non-SSL en-
              crypted connections.

              This mode could also be useful for SSH tunnels  since  it  means
              only one port needs to be redirected.

              The -httpsredir option may also be useful for this mode when us-
              ing an SSH tunnel as well as for router port redirections.

              Note that the  -env  X11VNC_HTTP_LISTEN_LOCALHOST=1  option  de-
              scribed  above  under  -httpsredir  applies for the LibVNCServer
              httpd server in all cases (ssl or not.)

       -ssh user@host:disp

              Create a remote listening port on machine "host" via a SSH  tun-
              nel using the -R rport:localhost:lport method. lport will be the
              local  x11vnc  listening  port,  so  a   connection   to   rport
              (5900+disp) on "host" will reach x11vnc.  E.g. fred@snoopy.com:0

              This could be useful if a firewall/router prevents incoming con-
              nections to the x11vnc machine, but the ssh machine  "host"  can
              be  reached  by the VNC viewer. "user@" is not needed unless the
              remote unix username differs from the current one.

              By default the remote sshd is usually configured to listen  only
              on  localhost  for rport, so the viewer may need to ssh -L redir
              to "host" as well (See SSVNC to automate this).  The  sshd  set-
              ting GatewayPorts enables listening on all interfaces for rport;
              viewers can reach it more easily.

              "disp" is the VNC display for the remote SSH side, e.g. 0 corre-
              sponds to port 5900, etc.  If disp is greater than 200 the value
              is used as the port.  Use a negative value to force a low  port,
              e.g. host:-80 will use port 80.

              If  ssh-agent  is  not active, then the ssh password needs to be
              entered in the terminal where x11vnc is running.

              By default the remote ssh will issue a 'sleep 300' to  wait  for
              the  incoming  connection  for  5  mins.   To  modify  this  use
              user@host:disp+secs.

              If the remote SSH server is on a non-standard port (i.e. not 22)
              use user@host:port:disp+secs.

              Note  that  the ssh process MAY NOT be killed when x11vnc exits.
              It tries by looking at ps(1) output.

       -usepw

              If no other password method was supplied on  the  command  line,
              first  look for ~/.vnc/passwd and if found use it with -rfbauth;
              next, look for ~/.vnc/passwdfile and use  it  with  -passwdfile;
              otherwise,   prompt   the   user   for   a  password  to  create
              ~/.vnc/passwd and use it with the -rfbauth option.  If  none  of
              these succeed x11vnc exits immediately.

       -storepasswd pass file

              Store  password pass as the VNC password in the file file.  Once
              the password is stored the program exits.  Use the password  via
              "-rfbauth file"

              If  called with no arguments, "x11vnc -storepasswd", the user is
              prompted  for  a  password  and  it  is  stored  in   the   file
              ~/.vnc/passwd.   Called with one argument, that will be the file
              to store the prompted password in.

       -nopw

              Disable the big warning message when you use x11vnc without some
              sort of password.

       -accept string

              Run  a  command (possibly to prompt the user at the X11 display)
              to decide whether an incoming client should be allowed  to  con-
              nect or not.  string is an external command run via system(3) or
              some special cases described below.  Be sure to quote string  if
              it contains spaces, shell characters, etc.  If the external com-
              mand returns 0 the client is accepted, otherwise the  client  is
              rejected.   See  below for an extension to accept a client view-
              only.

              If x11vnc is running as root (say from inetd(8) or from  display
              managers xdm(1) , gdm(1) , etc), think about the security impli-
              cations carefully before supplying this option (likewise for the
              -gone option).

              Environment:  The RFB_CLIENT_IP environment variable will be set
              to the incoming client IP number and the port in RFB_CLIENT_PORT
              (or   -1   if   unavailable).    Similarly,   RFB_SERVER_IP  and
              RFB_SERVER_PORT (the x11vnc side of the connection), are set  to
              allow  identification  of  the  tcp virtual circuit.  The x11vnc
              process id will be in RFB_X11VNC_PID,  a  client  id  number  in
              RFB_CLIENT_ID,  and  the  number  of  other connected clients in
              RFB_CLIENT_COUNT.  RFB_MODE will be "accept".  RFB_STATE will be
              PROTOCOL_VERSION, SECURITY_TYPE, AUTHENTICATION, INITIALISATION,
              NORMAL, or UNKNOWN indicating up to which state the  client  has
              achieved.   RFB_LOGIN_VIEWONLY  will  be  0, 1, or -1 (unknown).
              RFB_USERNAME, RFB_LOGIN_TIME, and RFB_CURRENT_TIME may  also  be
              set.

              If  string  is "popup" then a builtin popup window is used.  The
              popup will time out after 120 seconds, use "popup:N"  to  modify
              the timeout to N seconds (use 0 for no timeout).

              In the case of "popup" and when the -unixpw option is specified,
              then a *second* window will be popped up after the user success-
              fully logs in via his UNIX password.  This time the user will be
              identified as UNIX:username@hostname, the "UNIX:"  prefix  indi-
              cates  which  user  the viewer logged as via -unixpw.  The first
              popup is only for whether to allow him to even  *try*  to  login
              via unix password.

              If  string  is "xmessage" then an xmessage(1) invocation is used
              for the command.  xmessage must be installed on the machine  for
              this to work.

              Both "popup" and "xmessage" will present an option for accepting
              the client "View-Only" (the client can only watch).  This option
              will  not be presented if -viewonly has been specified, in which
              case the entire display is view only.

              If the user supplied command is  prefixed  with  something  like
              "yes:0,no:*,view:3  mycommand  ..." then this associates the nu-
              merical command return code with the  actions:  accept,  reject,
              and accept-view-only, respectively.  Use "*" instead of a number
              to indicate the default action (in case the command  returns  an
              unexpected value).  E.g. "no:*" is a good choice.

              Note  that  x11vnc blocks while the external command or popup is
              running (other clients may see no updates during  this  period).
              So  a person sitting a the physical display is needed to respond
              to an popup prompt. (use a 2nd x11vnc if you lock yourself out).

              More -accept tricks: use "popupmouse" to only allow mouse clicks
              in the builtin popup to be recognized.  Similarly use "popupkey"
              to only recognize keystroke responses.  These are to help  avoid
              the  user accidentally accepting a client by typing or clicking.
              All 3 of the popup keywords can be followed by +N+M to supply  a
              position  for  the  popup  window.  The default is to center the
              popup window.

       -afteraccept string

              As -accept, except to run a user supplied command after a client
              has  been  accepted  and  authenticated. RFB_MODE will be set to
              "afteraccept" and the other RFB_* variables are as  in  -accept.
              Unlike  -accept,  the  command return code is not interpreted by
              x11vnc.  Example: -afteraccept 'killall xlock &'

       -gone string

              As -accept, except to run a user supplied command when a  client
              goes away (disconnects).  RFB_MODE will be set to "gone" and the
              other RFB_* variables are as in -accept.   The  "popup"  actions
              apply  as  well.  Unlike -accept, the command return code is not
              interpreted by x11vnc.  Example: -gone 'xlock &'

       -users list

              If x11vnc is started as root (say from inetd(8) or from  display
              managers  xdm(1) , gdm(1) , etc), then as soon as possible after
              connections to the X display are established try  to  switch  to
              one  of the users in the comma separated list.  If x11vnc is not
              running as root this option is ignored.

              Why use this option?  In general it is not needed  since  x11vnc
              is  already  connected to the X display and can perform its pri-
              mary functions.  The option was added to make some of  the  *ex-
              ternal* utility commands x11vnc occasionally runs work properly.
              In particular under GNOME  and  KDE  to  implement  the  "-solid
              color" feature external commands (gconftool-2 and dcop) unfortu-
              nately must be run as  the  user  owning  the  desktop  session.
              Since  this  option  switches  userid it also affects the userid
              used to run the processes for the -accept and -gone options.  It
              also affects the ability to read files for options such as -con-
              nect, -allow, and -remap and also the ultra and tight filetrans-
              fer  feature  if  enabled.   Note that the -connect file is also
              sometimes written to.

              So be careful with this option since in some situations its  use
              can decrease security.

              In general the switch to a user will only take place if the dis-
              play can still be successfully opened as that user (this is pri-
              marily  to  try to guess the actual owner of the session). Exam-
              ple: "-users fred,wilma,betty".  Note  that  a  malicious  local
              user  "barney"  by  quickly  using "xhost +" when logging in may
              possibly get the x11vnc process to switch to user "fred".   What
              happens next?

              Under  display  managers it may be a long time before the switch
              succeeds (i.e. a user logs in).  To instead make it switch imme-
              diately  regardless  if  the  display can be reopened prefix the
              username with the "+" character. E.g. "-users +bob"  or  "-users
              +nobody".

              The  latter (i.e. switching immediately to user "nobody") is the
              only obvious use of the -users option that increases security.

              Use the following notation to associate a  group  with  a  user:
              user1.group1,user2.group2,...    Note  that  initgroups(2)  will
              still be called first to try to switch to ALL of a user's groups
              (primary  and  additional  groups).  Only if that fails or it is
              not available then the single group specified as above  (or  the
              user's  primary group if not specified) is switched to with set-
              gid(2).  Use -env X11VNC_SINGLE_GROUP=1 to prevent trying  init-
              groups(2)  and  only  switch  to the single group.  This sort of
              setting is only really needed to make the ultra or  tight  file-
              transfer  permissions  work properly. This format applies to any
              comma separated list of users, even the special  "="  modes  de-
              scribed below.

              In  -unixpw  mode,  if "-users unixpw=" is supplied then after a
              user authenticates himself via  the  -unixpw  mechanism,  x11vnc
              will try to switch to that user as though "-users +username" had
              been supplied.  If you want to limit which users  this  will  be
              done for, provide them as a comma separated list after "unixpw="
              Groups can also be specified as described above.

              Similarly, in -ssl mode, if "-users sslpeer=" is  supplied  then
              after  an SSL client authenticates with his cert (the -sslverify
              option is required for this) x11vnc will extract a UNIX username
              from  the  "emailAddress"  field  (username@hostname.com) of the
              "Subject" of the x509 SSL cert and then try to  switch  to  that
              user  as  though  "-users  +username" had been supplied.  If you
              want to limit which users this will be done for, provide them as
              a  comma  separated  list  after  "sslpeer=".   Set the env. var
              X11VNC_SSLPEER_CN to use the Common Name (normally  a  hostname)
              instead of the Email field.

              NOTE:  for sslpeer= mode the x11vnc administrator must take care
              that any client certs he adds to -sslverify  have  the  intended
              UNIX  username  in the "emailAddress" field of the cert.  Other-
              wise a user may be able to log in as another.  This command  can
              be  of  use  in checking: "openssl x509 -text -in file.crt", see
              the "Subject:" line.  Also, along with  the  normal  RFB_*  env.
              vars.   (see   -accept)   passed   to  external  cmd=  commands,
              RFB_SSL_CLIENT_CERT will be set to the client's x509 certificate
              string.

              The sslpeer= mode can aid finding X sessions via the FINDDISPLAY
              and FINDCREATEDISPLAY mechanisms.

              To immediately switch to a user *before* connections  to  the  X
              display  are  made  or  any  files opened use the "=" character:
              "-users =bob".  That user needs to be able to open the X display
              and any files of course.

              The  special  user  "guess=" means to examine the utmpx database
              (see who(1) ) looking for a user attached to the display  number
              (from DISPLAY or -display option) and try him/her.  To limit the
              list of guesses, use: "-users guess=bob,betty".

              Even more sinister is the special user "lurk=" that means to try
              to  guess the DISPLAY from the utmpx login database as well.  So
              it "lurks" waiting for anyone to log into an X session and  then
              connects  to  it.   Specify a list of users after the = to limit
              which users will be tried.   To  enable  a  different  searching
              mode,  if  the  first user in the list is something like ":0" or
              ":0-2" that indicates a range of DISPLAY numbers  that  will  be
              tried (regardless of whether they are in the utmpx database) for
              all users that are logged in.  Also see the "-display  WAIT:..."
              functionality.    Examples:  "-users  lurk="  and  also  "-users
              lurk=:0-1,bob,mary"

              Be especially careful using  the  "guess="  and  "lurk="  modes.
              They  are not recommended for use on machines with untrustworthy
              local users.

       -noshm

              Do not use the MIT-SHM extension for the polling.   Remote  dis-
              plays  can  be  polled  this  way: be careful this can use large
              amounts of network bandwidth.  This is also of use if the  local
              machine has a limited number of shm segments and -onetile is not
              sufficient.

       -flipbyteorder

              Sometimes needed if remotely polled host has  different  endian-
              ness.  Ignored unless -noshm is set.

       -onetile

              Do  not use the new copy_tiles() framebuffer mechanism, just use
              1 shm tile for polling.  Limits shm segments used to 3.

              To disable  any  automatic  shm  reduction  set  the  env.  var.
              X11VNC_NO_LIMIT_SHM.

       -solid [color]

              To  improve  performance,  when VNC clients are connected try to
              change the desktop background to a solid color.  The [color]  is
              optional:  the  default  color  is "cyan4".  For a different one
              specify the X color (rgb.txt name, e.g. "darkblue" or  numerical
              "#RRGGBB").

              Currently  this  option only works on GNOME, KDE, CDE, XFCE, and
              classic X (i.e. with the background image on the  root  window).
              The  "gconftool-2",  "dcop" and "xfconf-query" external commands
              are run for GNOME, KDE, and XFCE respectively.  This also  works
              on  native  MacOSX.   (There is no color selection for MacOSX or
              XFCE.)  Other desktops won't work, (send  us  the  corresponding
              commands  if you find them).  If x11vnc is running as root ( in-
              etd(8) or gdm(1) ), the -users option may be needed  for  GNOME,
              KDE,  XFCE.  If x11vnc guesses your desktop incorrectly, you can
              force it by  prefixing  color  with  "gnome:",  "kde:",  "cde:",
              "xfce:", or "root:".

              Update: -solid no longer works on KDE4.

              This  mode  works  in a limited way on the Mac OS X Console with
              one color ('kelp') using the screensaver writing  to  the  back-
              ground.  Look in "~/Library/Screen Savers" for VncSolidColor.png
              to change the color.

       -blackout string

              Black out rectangles on the screen. string is a comma  separated
              list  of  WxH+X+Y type geometries for each rectangle.  If one of
              the items on the list is the string "noptr"  the  mouse  pointer
              will not be allowed to go into a blacked out region.

       -xinerama, -noxinerama

              If  your  screen is composed of multiple monitors glued together
              via XINERAMA, and that screen is not  a  rectangle  this  option
              will  try  to  guess  the areas to black out (if your system has
              libXinerama).  default: -xinerama

              In general, we have noticed on XINERAMA displays you may need to
              use  the  "-xwarppointer" option if the mouse pointer misbehaves
              and it is enabled by default. Use "-noxwarppointer"  if  you  do
              not want this.

       -xtrap

              Use the DEC-XTRAP extension for keystroke and mouse input inser-
              tion.  For use on legacy systems, e.g. X11R5, running an  incom-
              plete  or missing XTEST extension.  By default DEC-XTRAP will be
              used if XTEST server grab control is missing, use -xtrap  to  do
              the keystroke and mouse insertion via DEC-XTRAP as well.

       -xrandr [mode]

              If the display supports the XRANDR (X Resize, Rotate and Reflec-
              tion) extension, and you expect XRANDR events to  occur  to  the
              display  while  x11vnc is running, this options indicates x11vnc
              should try to respond to them (as opposed to simply crashing  by
              assuming  the  old  screen size).  See the xrandr(1) manpage and
              run 'xrandr -q' for more info.  [mode] is optional and described
              below.

              Since  watching  for XRANDR events and trapping errors increases
              polling overhead, only use this option if XRANDR changes are ex-
              pected.  For example on a rotatable screen PDA or laptop, or us-
              ing a XRANDR-aware Desktop where you resize often.  It  is  best
              to  be  viewing with a vncviewer that supports the NewFBSize en-
              coding, since it knows how to  react  to  screen  size  changes.
              Otherwise,  LibVNCServer tries to do so something reasonable for
              viewers that cannot do this  (portions  of  the  screen  may  be
              clipped, unused, etc).

              Note:  the default now is to check for XRANDR events, but do not
              trap every X call that may fail due  to  resize.   If  a  resize
              event is received, the full -xrandr mode is enabled.  To disable
              even checking for events supply: -noxrandr.

              "mode" defaults to "resize", which means create a new,  resized,
              framebuffer  and  hope  all  viewers  can  cope with the change.
              "newfbsize" means first disconnect all viewers that do not  sup-
              port  the  NewFBSize  VNC  encoding,  and then resize the frame-
              buffer.  "exit" means disconnect all viewer  clients,  and  then
              terminate x11vnc.

       -rotate string

              Rotate  and/or  flip the framebuffer view exported by VNC.  This
              transformation is independent of XRANDR and is done in  software
              in  main memory and so may be slower.  This mode could be useful
              on a handheld with portrait or landscape modes that do not  cor-
              respond to the scanline order of the actual framebuffer.  string
              can be:

              x     flip along x-axis y      flip  along  y-axis  xy      flip
              along  x-  and  y-axes  +90      rotate 90 degrees clockwise -90
              rotate 90 degrees counter-clockwise +90x     rotate  90  degrees
              CW,  then  flip along x +90y     rotate 90 degrees CW, then flip
              along y

              these give all possible rotations and reflections.

              Aliases: same as xy:  yx, +180, -180, 180 same as -90: +270, 270
              same as +90: 90, (ditto for 90x, 90y)

              Like  -scale,  this transformation is applied at the very end of
              any chain of framebuffer transformations and so any options with
              geometries,  e.g.  -blackout,  -clip,  etc.  are relative to the
              original X (or -rawfb) framebuffer, not the final  one  sent  to
              VNC viewers.

              If  you do not want the cursor shape to be rotated prefix string
              with "nc:", e.g. "nc:+90", "nc:xy", etc.

       -padgeom WxH

              Whenever a new vncviewer connects, the framebuffer  is  replaced
              with  a  fake,  solid black one of geometry WxH.  Shortly after-
              wards the framebuffer is replaced with the real  one.   This  is
              intended  for  use with vncviewers that do not support NewFBSize
              and one wants to make sure the initial viewer geometry  will  be
              big enough to handle all subsequent resizes (e.g. under -xrandr,
              -remote id:windowid, rescaling, etc.)

              In -unixpw mode this sets the size of  the  login  screen.   Use
              "once:WxH" it ignore padgeom after the login screen is set up.

       -o logfile

              Write  stderr  messages to file logfile instead of to the termi-
              nal.  Same as "-logfile file".  To append to the file  use  "-oa
              file"  or  "-logappend  file".   If  logfile contains the string
              "%VNCDISPLAY" it is expanded to the vnc display  (the  name  may
              need to be guessed at.)  "%HOME" works too.

       -flag file

              Write  the  "PORT=NNNN" (e.g. PORT=5900) string to file in addi-
              tion to stdout.  This option could be useful by  wrapper  script
              to detect when x11vnc is ready.

       -rmflag file

              Remove  file at exit to signal when x11vnc is done.  The file is
              created at startup if it does not already exist or  if  file  is
              prefixed with "create:".  If the file is created, the x11vnc PID
              is placed in the file.  Otherwise  the  files  contents  is  not
              changed.  Use prefix "nocreate:" to prevent creation.

       -rc filename

              Use filename instead of $HOME/.x11vncrc for rc file.

       -norc

              Do not process any .x11vncrc file for options.

       -env VAR=VALUE

              Set  the  environment  variable 'VAR' to value 'VALUE' at x11vnc
              startup.  This is a convenience utility to  avoid  shell  script
              wrappers,  etc. to set the env. var.  You may specify as many of
              these as needed on the command line.

       -prog /path/to/x11vnc

              Set the full path to the x11vnc program for cases when it cannot
              be determined from argv[0] (e.g. tcpd/inetd)

       -h, -help

              Print  this  help  text.   -?,  -opts              Only list the
              x11vnc options.

       -V, -version

              Print program version and last modification date.

       -license

              Print out license information.  Same as -copying and -warranty.

       -dbg

              Instead of exiting after cleaning up, run a simple "debug  crash
              shell" when fatal errors are trapped.

       -q, -quiet

              Be  quiet  by printing less informational output to stderr. (use
              -noquiet to undo an earlier -quiet.)

              The -quiet option does not eliminate all  informational  output,
              it  only  reduces  it.   It  is  ignored in most auxiliary usage
              modes,  e.g.  -storepasswd.   To  eliminate  all   output   use:
              2>/dev/null 1>&2, etc.

       -v, -verbose

              Print out more information to stderr.

       -bg

              Go  into  the background after screen setup.  Messages to stderr
              are lost unless -o logfile is used.  Something like  this  could
              be useful in a script:

              port=`ssh -t $host "x11vnc -display :0 -bg" | grep PORT`

              port=`echo "$port" | sed -e 's/PORT=//'`

              port=`expr $port - 5900`

              vncviewer $host:$port

       -modtweak, -nomodtweak

              Option  -modtweak  automatically  tries  to adjust the AltGr and
              Shift modifiers for differing language keyboards between  client
              and  host.  Otherwise, only a single key press/release of a Key-
              code is simulated (i.e. ignoring the  state  of  the  modifiers:
              this usually works for identical keyboards).  Also useful in re-
              solving cases where a Keysym is bound to multiple keys (e.g. "<"
              + ">" and "," + "<" keys).  Default: -modtweak

              If you are having trouble with with keys and -xkb or -noxkb, and
              similar things don't help, try -nomodtweak.

              On some HP-UX systems it is been noted that  they  have  an  odd
              keymapping  where a single keycode will have a keysym, e.g. "#",
              up to three times.  You can check via "xmodmap -pk" or  the  -dk
              option.   The failure is when you try to type "#" it yields "3".
              If you see this problem try  setting  the  environment  variable
              MODTWEAK_LOWEST=1 to see if it helps.

       -xkb, -noxkb

              When  in  modtweak  mode,  use the XKEYBOARD extension (if the X
              display supports it) to do the modifier tweaking.  This is  pow-
              erful and should be tried if there are still keymapping problems
              when using -modtweak by itself.  The default is to check whether
              some  common keysyms, e.g. !, @, [, are only accessible via -xkb
              mode and if so then automatically enable the mode.   To  disable
              this automatic detection use -noxkb.

              When  -xkb mode is active you can set these env. vars.  They ap-
              ply only when there is ambiguity as to which key to choose  (i.e
              the mapping is not one-to-one).  NOKEYHINTS=1: for up ascii key-
              strokes do not use score hints saved when the  key  was  pressed
              down.  NOANYDOWN=1: for up keystrokes do not resort to searching
              through keys that are currently pressed down.   KEYSDOWN=N:  re-
              member  the  last  N keys press down for tie-breaking when an up
              keystroke comes in.

       -capslock

              When in -modtweak (the default) or -xkb mode, if a keysym in the
              range A-Z comes in check the X server to see if the Caps_Lock is
              set.  If it is do not artificially press Shift to  generate  the
              keysym.   This  will enable the CapsLock key to behave correctly
              in some circumstances: namely *both* the VNC viewer machine  and
              the  x11vnc  X server are in the CapsLock on state.  If one side
              has CapsLock on and the other off and the keyboard is not behav-
              ing  as  you  think  it  should  you should correct the CapsLock
              states (hint: pressing CapsLock inside and outside of the viewer
              can  help  toggle them both to the correct state).  However, for
              best results do not use this option, but  rather  *only*  enable
              CapsLock  on the VNC viewer side (i.e. by pressing CapsLock out-
              side of the viewer window, also -skip_lockkeys below).  Also try
              -nomodtweak for a possible workaround.

       -skip_lockkeys, -noskip_lockkeys

              Have   x11vnc   ignore   all  Caps_Lock,  Shift_Lock,  Num_Lock,
              Scroll_Lock keysyms received from  viewers.   The  idea  is  you
              press  Caps_Lock on the VNC Viewer side but that does not change
              the lock state in the x11vnc-side X server.   Nevertheless  your
              capitalized  letters  come in over the wire and are applied cor-
              rectly to the x11vnc-side X server.   Note  this  mode  probably
              won't  do what you want in -nomodtweak mode.  Also, a kludge for
              KP_n digits is always done in this mode: they are mapped to reg-
              ular  digit  keysyms.  See also -capslock above.  The default is
              -noskip_lockkeys.

       -skip_keycodes string

              Ignore the comma separated list of  decimal  keycodes.   Perhaps
              these are keycodes not on your keyboard but your X server thinks
              exist.  Currently only applies to -xkb mode.  Use this option to
              help  x11vnc in the reverse problem it tries to solve: Keysym ->
              Keycode(s) when ambiguities exist (more  than  one  Keycode  per
              Keysym).   Run  'xmodmap  -pk' to see your keymapping.  Example:
              "-skip_keycodes 94,114"

       -sloppy_keys

              Experimental option that tries to correct some "sloppy" key  be-
              havior.   E.g. if at the viewer you press Shift+Key but then re-
              lease the Shift before Key that could give  rise  to  extra  un-
              wanted  characters  (usually only between keyboards of different
              languages).  Only use this option if you observe  problems  with
              some keystrokes.

       -skip_dups, -noskip_dups

              Some  VNC viewers send impossible repeated key events, e.g. key-
              down, key-down, key-up, key-up all for the same key, or 20 downs
              in a row for the same modifier key!  Setting -skip_dups means to
              skip these duplicates and just process the  first  event.  Note:
              some  VNC viewers assume they can send down's without the corre-
              sponding up's and so you should not set this  option  for  these
              viewers   (symptom:   some  keys  do  not  autorepeat)  Default:
              -noskip_dups

       -add_keysyms, -noadd_keysyms

              If a Keysym is received from a VNC viewer and that  Keysym  does
              not exist in the X server, then add the Keysym to the X server's
              keyboard mapping on an unused key.  Added Keysyms  will  be  re-
              moved   periodically  and  also  when  x11vnc  exits.   Default:
              -add_keysyms

       -clear_mods

              At startup and exit clear the modifier keys  by  sending  KeyRe-
              lease  for  each  one.  The Lock modifiers are skipped.  Used to
              clear the state if the display was accidentally  left  with  any
              pressed down.

       -clear_keys

              As  -clear_mods,  except  try  to release ANY pressed key.  Note
              that this option and -clear_mods can  interfere  with  a  person
              typing at the physical keyboard.

       -clear_all

              As  -clear_keys,  except  try  to release any CapsLock, NumLock,
              etc. locks as well.

       -remap string

              Read Keysym remappings from file named string.   Format  is  one
              pair of Keysyms per line (can be name or hex value) separated by
              a space.  If no file named string exists, it is  instead  inter-
              preted    as    this    form:    key1-key2,key3-key4,...     See
              <X11/keysymdef.h> header file for a list of Keysym names, or use
              xev(1).

              To  map a key to a button click, use the fake Keysyms "Button1",
              ..., etc. E.g: "-remap Super_R-Button2" (useful for pasting on a
              laptop)

              I  use  these  if  the machine I am viewing from does not have a
              scrollwheel or I don't like using the one it has:

              -remap Super_R-Button4,Menu-Button5 -remap KP_Add-Button4,KP_En-
              ter-Button5

              the former would be used on a PC, the latter on a MacBook.  This
              way those little used keys can be used to generate  bigger  hops
              than  the  Up  and  Down arrows provide.  One can scroll through
              text or web pages more quickly this way  (especially  if  x11vnc
              scroll detection is active.)

              Use Button44, Button12, etc. for multiple clicks.

              To  disable  a keysym (i.e. make it so it will not be injected),
              remap it to "NoSymbol" or "None".

              Dead keys: "dead" (or silent, mute) keys are keys  that  do  not
              produce  a  character  but  must be followed by a 2nd keystroke.
              This is often used for accenting characters, e.g. to put "`"  on
              top  of  "a"  by  pressing the dead key and then "a".  Note that
              this interpretation is not part of core X11, it  is  up  to  the
              toolkit  or  application to decide how to react to the sequence.
              The X11 names for these keysyms are "dead_grave",  "dead_acute",
              etc.  However some VNC viewers send the keysyms "grave", "acute"
              instead thereby disabling the accenting.  To  work  around  this
              -remap can be used.  For example "-remap grave-dead_grave,acute-
              dead_acute"

              As a convenience, "-remap DEAD" applies these remaps:

                    g     grave-dead_grave
                    a     acute-dead_acute
                    c     asciicircum-dead_circumflex
                    t     asciitilde-dead_tilde
                    m     macron-dead_macron
                    b     breve-dead_breve
                    D     abovedot-dead_abovedot
                    d     diaeresis-dead_diaeresis
                    o     degree-dead_abovering
                    A     doubleacute-dead_doubleacute
                    r     caron-dead_caron
                    e     cedilla-dead_cedilla

              If you just want a subset  use  the  first  letter  label,  e.g.
              "-remap  DEAD=ga"  to  get the first two.  Additional remaps may
              also be supplied via commas, e.g.  "-remap  DEAD=ga,Super_R-But-
              ton2".   Finally, "DEAD=missing" means to apply all of the above
              as long as the left hand  member  is  not  already  in  the  X11
              keymap.

       -norepeat, -repeat

              Option  -norepeat  disables  X  server  key auto repeat when VNC
              clients are connected and VNC keyboard input  is  not  idle  for
              more  than  5 minutes.  This works around a repeating keystrokes
              bug (triggered by long processing delays between  key  down  and
              key  up  client events: either from large screen changes or high
              latency).  Default: -norepeat

              You can set the env. var. X11VNC_IDLE_TIMEOUT to the  number  of
              idle seconds you want (5min = 300secs).

              Note: your VNC viewer side will likely do autorepeating, so this
              is no loss unless someone is simultaneously at the real  X  dis-
              play.

              Use  "-norepeat  N" to set how many times norepeat will be reset
              if something else (e.g. X session manager) undoes it.   The  de-
              fault is 2.  Use a negative value for unlimited resets.

       -nofb

              Ignore  video  framebuffer:  only  process keyboard and pointer.
              Intended for use with Win2VNC and x2vnc dual-monitor setups.

       -nobell

              Do not watch for XBell events. (no beeps will  be  heard)  Note:
              XBell monitoring requires the XKEYBOARD extension.

       -nosel

              Do  not  manage  exchange  of  X selection/cutbuffer between VNC
              viewers and the X server at all.

       -noprimary

              Do not poll the PRIMARY selection for changes to  send  back  to
              clients.  (PRIMARY is still set on received changes, however).

       -nosetprimary

              Do  not  set the PRIMARY selection for changes received from VNC
              clients.

       -noclipboard

              Do not poll the CLIPBOARD selection for changes to send back  to
              clients.  (CLIPBOARD is still set on received changes, however).

       -nosetclipboard

              Do not set the CLIPBOARD selection for changes received from VNC
              clients.

       -seldir string

              If direction string is "send", only send the selection to  view-
              ers,  and if it is "recv" only receive it from viewers.  To work
              around apps setting the selection too frequently and messing  up
              the  other  end.  You can actually supply a comma separated list
              of directions, including "debug" to turn on debugging output.

       -cursor [mode], -nocursor

              Sets how the pointer cursor shape  (little  icon  at  the  mouse
              pointer)  should  be handled.  The "mode" string is optional and
              is described below.  The default is to show some sort of  cursor
              shape(s).   How this is done depends on the VNC viewer and the X
              server.  Use -nocursor to disable cursor shapes completely.

              Some VNC viewers support the TightVNC CursorPosUpdates and  Cur-
              sorShapeUpdates  extensions (cuts down on network traffic by not
              having to send the  cursor  image  every  time  the  pointer  is
              moved),  in which case these extensions are used (see -nocursor-
              shape and -nocursorpos below to disable).  For other viewers the
              cursor  shape  is written directly to the framebuffer every time
              the pointer is moved or changed and gets  sent  along  with  the
              other framebuffer updates.  In this case, there will be some lag
              between the vnc viewer pointer and the remote cursor position.

              If the X display supports retrieving the cursor  shape  informa-
              tion  from  the  X server, then the default is to use that mode.
              On Solaris this can be done with  the  SUN_OVL  extension  using
              -overlay  (see  also  the  -overlay_nocursor option).  A similar
              overlay scheme is used on IRIX.  Xorg (e.g.  Linux)  and  recent
              Solaris  Xsun  servers  support the XFIXES extension to retrieve
              the exact cursor shape from the X server.  If XFIXES is  present
              it  is  preferred over Overlay and is used by default (see -nox-
              fixes below).  This can be disabled  with  -nocursor,  and  also
              some values of the "mode" option below.

              Note that under XFIXES cursors with transparency (alpha channel)
              will usually not be exactly represented and one may find Overlay
              preferable.  See also the -alphacut and -alphafrac options below
              as fudge factors to try to improve  the  situation  for  cursors
              with transparency for a given theme.

              The  "mode"  string  can  be used to fine-tune the displaying of
              cursor shapes.  It can be used the following ways:

              "-cursor arrow" - just show the standard arrow nothing  more  or
              nothing less.

              "-cursor none" - same as "-nocursor"

              "-cursor  X" - when the cursor appears to be on the root window,
              draw the familiar X shape.  Some desktops such as GNOME cover up
              the root window completely, and so this will not work, try "X1",
              etc, to try to shift the tree depth.  On high latency  links  or
              slow  machines there will be a time lag between expected and the
              actual cursor shape.

              "-cursor some" - like "X" but use additional heuristics  to  try
              to  guess if the window should have a windowmanager-like resizer
              cursor or a text input I-beam cursor.  This is a complete  hack,
              but  may be useful in some situations because it provides a lit-
              tle more feedback about the cursor shape.

              "-cursor most" - try to show as many cursors as possible.  Often
              this  will  only  be  the  same as "some" unless the display has
              overlay visuals or XFIXES extensions available.  On Solaris  and
              IRIX  if  XFIXES  is  not  available,  -overlay mode will be at-
              tempted.

       -cursor_drag

              Show cursor shape changes even when the mouse is  being  dragged
              with a mouse button down.  This is useful if you want to be able
              to see Drag-and-Drop cursor icons, etc.

       -arrow n

              Choose an alternate "arrow" cursor from a  set  of  some  common
              ones.   n  can  be 1 to 6.  Default is: 1 Ignored when in XFIXES
              cursor-grabbing mode.

       -noxfixes

              Do not use the XFIXES extension to draw the exact  cursor  shape
              even if it is available.

              Note:  To  work around a crash in Xorg 1.5 and later some people
              needed to use -noxfixes.  The Xorg crash occurred right after  a
              Display Manager (e.g. GDM) login.  Starting with x11vnc 0.9.9 it
              tries to automatically avoid using XFIXES until  it  is  sure  a
              window manager is running.  See the -reopen option for more info
              and how to use X11VNC_AVOID_WINDOWS=never to disable it.

       -alphacut n

              When using the XFIXES extension for the  cursor  shape,  cursors
              with  transparency  will  not  usually be displayed exactly (but
              opaque ones will).  This option sets n as a cutoff  for  cursors
              that have transparency ("alpha channel" with values ranging from
              0 to 255) Any cursor pixel with alpha value less than n  becomes
              completely  transparent.   Otherwise  the  pixel  is  completely
              opaque.  Default 240

       -alphafrac fraction

              With the threshold in -alphacut some cursors will become  almost
              completely  transparent  because their alpha values are not high
              enough.  For those cursors  adjust  the  alpha  threshold  until
              fraction  of  the  non-zero  alpha channel pixels become opaque.
              Default 0.33

       -alpharemove

              By default, XFIXES cursors pixels with transparency have the al-
              pha  factor multiplied into the RGB color values (i.e. that cor-
              responding to blending the  cursor  with  a  black  background).
              Specify  this  option  to  remove  the alpha factor. (useful for
              light colored semi-transparent cursors).

       -noalphablend

              In XFIXES mode do not send cursor alpha channel data to  LibVNC-
              Server.   The default is to send it.  The alphablend effect will
              only be visible in -nocursorshape mode or for clients with  cur-
              sorshapeupdates  turned  off. (However there is a hack for 32bpp
              with depth 24, it uses the extra 8 bits to store  cursor  trans-
              parency  for use with a hacked vncviewer that applies the trans-
              parency locally.  See the FAQ for more info).

       -nocursorshape

              Do not use the TightVNC  CursorShapeUpdates  extension  even  if
              clients support it.  See -cursor above.

       -cursorpos, -nocursorpos

              Option  -cursorpos enables sending the X cursor position back to
              all vnc clients that support the TightVNC  CursorPosUpdates  ex-
              tension.  Other clients will be able to see the pointer motions.
              Default: -cursorpos

       -xwarppointer, -noxwarppointer

              Move the pointer with XWarpPointer(3X) instead of the XTEST  ex-
              tension.  Use this as a workaround if the pointer motion behaves
              incorrectly, e.g.  on touchscreens or other non-standard setups.

              It is also sometimes needed on XINERAMA displays and is  enabled
              by  default if XINERAMA is found to be active.  To prevent this,
              use -noxwarppointer.

       -always_inject

              Even if there is no displacement (dx = dy = 0) for a  VNC  mouse
              event  force  the  pointer to the indicated x,y position anyway.
              Recent (2009) gui toolkits (gnome) have problems  with  x11vnc's
              original  mouse input injection method.  So x11vnc's mouse input
              injection method has been modified.  To regain the OLD  behavior
              use  this option: -always_inject.  Then x11vnc will always force
              positioning the mouse to the x,y position even if that  position
              has not changed since the previous VNC input event.

              The  first place this problem was noticed was in gnome terminal:
              if you pressed and released mouse button 3, a  menu  was  posted
              and  then its first element 'New Terminal Window' was activated.
              This was because x11vnc injected the mouse position twice:  once
              on  ButtonPress  and again on ButtonRelease.  The toolkit inter-
              preted the 2nd one as mouse motion even though the mouse  hadn't
              moved.   So  now  by default x11vnc tries to avoid injecting the
              2nd one.

              Note that with the new default x11vnc will be oblivious  to  ap-
              plications moving the pointer (warping) or the user at the phys-
              ical display moving it.  So it might, e.g., inject ButtonRelease
              at  the  wrong  position.  If this (or similar scenarios) causes
              problems in your environment, specify -always_inject for the old
              method.

       -buttonmap string

              String  to remap mouse buttons.  Format: IJK-LMN, this maps but-
              tons I -> L, etc., e.g.  -buttonmap 13-31

              Button presses can also be mapped to keystrokes: replace a  but-
              ton   digit   on   the   right  of  the  dash  with  :<sym>:  or
              :<sym1>+<sym2>: etc. for multiple  keys.  For  example,  if  the
              viewing  machine  has a mouse-wheel (buttons 4 5) but the x11vnc
              side does not, these will do scrolls:

              -buttonmap 12345-123:Prior::Next:

              -buttonmap 12345-123:Up+Up+Up::Down+Down+Down:

              See <X11/keysymdef.h> header file for a list of Keysyms, or  use
              the  xev(1)  program.  Note: mapping of button clicks to Keysyms
              may not work if -modtweak or -xkb is needed for the Keysym.

              If you include a modifier like "Shift_L" the modifier's  up/down
              state is toggled, e.g. to send "The" use :Shift_L+t+Shift_L+h+e:
              (the 1st one is shift down and the 2nd one is shift up).  (note:
              the  initial  state of the modifier is ignored and not reset) To
              include button events use "Button1", ... etc.

              -buttonmap currently does not  work  on  MacOSX  console  or  in
              -rawfb mode.

              Workaround:  use -buttonmap IJ...-LM...=n to limit the number of
              mouse buttons to n, e.g. 123-123=3.  This  will  prevent  x11vnc
              from  crashing  if the X server reports there are 5 buttons (4/5
              scroll wheel), but there are only really 3.

       -nodragging

              Do not update the display during mouse  dragging  events  (mouse
              button  held  down).   Greatly improves response on slow setups,
              but you lose all visual feedback for drags, text selection,  and
              some menu traversals.  It overrides any -pointer_mode setting.

       -ncache n

              Client-side  caching  scheme.  Framebuffer memory n (an integer)
              times that of the full display is  allocated  below  the  actual
              framebuffer  to cache screen contents for rapid retrieval.  So a
              W x H frambuffer is expanded to a W x (n+1)*H  one.   Use  0  to
              disable.

              The n is actually optional, the default is 10.

              For this and the other -ncache* options below you can abbreviate
              "-ncache" with "-nc".  Also, "-nonc" is the same as "-ncache 0"

              This is an experimental option, currently implemented in an awk-
              ward  way  in that in the VNC Viewer you can see the pixel cache
              contents if you scroll down, etc.   So  you  will  have  to  set
              things  up so you can't see that region.  If this method is suc-
              cessful, the changes required for clients to do this  less  awk-
              wardly will be investigated.

              The  SSVNC  viewer  does  a good job at automatically hiding the
              pixel cache region.  Or use SSVNC's -ycrop option to  explicitly
              hide the region.

              Note  that  this  mode consumes a huge amount of memory, both on
              the x11vnc server side and on the VNC Viewer side.  If n=2  then
              the  amount  of  RAM used is roughly tripled for both x11vnc and
              the VNC Viewer.  As a rule of  thumb,  note  that  1280x1024  at
              depth 24 is about 5MB of pixel data.

              For  reasonable response when cycling through 4 to 6 large (e.g.
              web browser) windows a value  n  of  6  to  12  is  recommended.
              (that's right: ~10X more memory...)

              Because of the way window backingstore and saveunders are imple-
              mented, n must be even.  It will be incremented by 1  if  it  is
              not.

              This  mode  also works for native MacOS X, but may not be as ef-
              fective as the X version.  This is due to a  number  of  things,
              one  is the drop-shadow compositing that leaves extra areas that
              need to be repaired (see -ncache_pad).  Another  is  the  window
              iconification  animations need to be avoided (see -macicontime).
              It appears the that the 'Scale' animation mode gives better  re-
              sults than the 'Genie' one.  Also, window event detection not as
              accurate as the X version.

       -ncache_cr

              In -ncache mode, try to do copyrect  opaque  window  moves/drags
              instead  of  wireframes  (this can induce painting errors).  The
              wireframe will still be used when moving a window whose save-un-
              ders has not yet been set or has been invalidated.

              Some  VNC  Viewers provide better response than others with this
              option.  On Unix,  realvnc  viewer  gives  smoother  drags  than
              tightvnc viewer.  Response may also be choppy if the server side
              machine is too slow.

              Sometimes on very slow modem connections, this actually gives an
              improvement  because no pixel data at all (not even the box ani-
              mation) is sent during the drag.

       -ncache_no_moveraise

              In -ncache mode, do not assume that moving a window  will  cause
              the window manager to raise it to the top of the stack.  The de-
              fault is to assume it does, and so at the beginning of any wire-
              frame, etc, window moves the window will be pushed to top in the
              VNC viewer.

       -ncache_no_dtchange

              In -ncache mode, do not try to guess when the desktop (viewport)
              changes  to another one (i.e. another workarea).  The default is
              to try to guess and when detected try  to  make  the  transition
              more smoothly.

       -ncache_no_rootpixmap

              In  -ncache  mode, do not try to snapshot the desktop background
              to use in guessing or reconstructing window save-unders.

       -ncache_keep_anims

              In -ncache mode, do not try to disable window manager animations
              and  other  effects  (that usually degrade ncache performance or
              cause painting errors).  The default is to try to  disable  them
              on KDE (but not GNOME) when VNC clients are connected.

              For  other  window managers or desktops that provide animations,
              effects, compositing, translucency, etc. that interfere with the
              -ncache method you will have to disable them manually.

       -ncache_old_wm

              In  -ncache  mode,  enable  some heuristics for old style window
              managers such as fvwm and twm.

       -ncache_pad n

              In -ncache mode, pad each window with n pixels for  the  caching
              rectangles.   This  can  be used to try to improve the situation
              with dropshadows or other compositing (e.g. MacOS X window  man-
              ager), although it could make things worse.  The default is 0 on
              Unix and 24 on MacOS X.

       -debug_ncache

              Turn on debugging and profiling output under -ncache.

       -wireframe [str], -nowireframe

              Try to detect window moves or resizes when  a  mouse  button  is
              held  down  and show a wireframe instead of the full opaque win-
              dow.  This is based completely on heuristics and may not  always
              work:  it  depends  on your window manager and even how you move
              things around.  See -pointer_mode below for  discussion  of  the
              "bogging down" problem this tries to avoid.  Default: -wireframe

              Shorter aliases:  -wf [str]  and -nowf

              The  value "str" is optional and, of course, is packed with many
              tunable parameters for this scheme:

              Format: shade,linewidth,percent,T+B+L+R,mod,t1+t2+t3+t4 Default:
              0xff,2,0,32+8+8+8,all,0.15+0.30+5.0+0.125

              If  you  leave nothing between commas: ",," the default value is
              used.  If you don't specify enough commas, the trailing  parame-
              ters are set to their defaults.

              "shade"  indicate  the  "color"  for  the  wireframe,  usually a
              greyscale: 0-255, however for 16 and 32bpp you  can  specify  an
              rgb.txt  X color (e.g. "dodgerblue") or a value > 255 is treated
              as RGB (e.g. red is 0xff0000).  "linewidth" sets  the  width  of
              the  wireframe  in pixels.  "percent" indicates to not apply the
              wireframe scheme to windows with area less than this percent  of
              the full screen.

              "T+B+L+R"  indicates  four  integers for how close in pixels the
              pointer has to be from the Top, Bottom, Left, or Right edges  of
              the  window  to  consider  wireframing.   This  is  a speedup to
              quickly exclude a window from being wireframed: set them all  to
              zero  to  not try the speedup (scrolling and selecting text will
              likely be slower).

              "mod" specifies if a button down event in the  interior  of  the
              window  with a modifier key (Alt, Shift, etc.) down should indi-
              cate a wireframe opportunity.  It can be "0" or "none"  to  skip
              it, "1" or "all" to apply it to any modifier, or "Shift", "Alt",
              "Control", "Meta", "Super", or "Hyper" to only  apply  for  that
              type of modifier key.

              "t1+t2+t3+t4"  specify  four floating point times in seconds: t1
              is how long to wait for the pointer to move, t2 is how  long  to
              wait  for  the window to start moving or being resized (for some
              window managers this can be rather long), t3 is how long to keep
              a wireframe moving before repainting the window. t4 is the mini-
              mum time between sending wireframe "animations".  If a slow link
              is  detected, these values may be automatically changed to some-
              thing better for a slow link.

       -nowireframelocal

              By default, mouse motion and button presses of a user sitting at
              the  LOCAL  display  are monitored for wireframing opportunities
              (so that the  changes  will  be  sent  efficiently  to  the  VNC
              clients).  Use this option to disable this behavior.

       -wirecopyrect mode, -nowirecopyrect

              Since  the  -wireframe mechanism evidently tracks moving windows
              accurately, a speedup can be obtained by telling the VNC viewers
              to  locally  copy the translated window region.  This is the VNC
              CopyRect encoding: the framebuffer update doesn't need  to  send
              the actual new image data.

              Shorter aliases:  -wcr [mode]  and -nowcr

              "mode" can be "never" (same as -nowirecopyrect) to never try the
              copyrect, "top" means only do it if the window was  not  covered
              by any other windows, and "always" means to translate the origi-
              nally unobscured region (this may  look  odd  as  the  remaining
              pieces come in, but helps on a slow link).  Default: "always"

              Note:  there  can be painting errors or slow response when using
              -scale so you may want to disable CopyRect in this case  "-wire-
              copyrect  never"  on  the command line or by remote-control.  Or
              you can also use the "-scale xxx:nocr" scale option.

       -debug_wireframe

              Turn on debugging info printout for  the  wireframe  heuristics.
              "-dwf" is an alias.  Specify multiple times for more output.

       -scrollcopyrect mode, -noscrollcopyrect

              Like -wirecopyrect, but use heuristics to try to guess if a win-
              dow has scrolled its contents  (either  vertically  or  horizon-
              tally).   This  requires  the RECORD X extension to "snoop" on X
              applications (currently for certain XCopyArea and XConfigureWin-
              dow  X protocol requests).  Examples: Hitting <Return> in a ter-
              minal window when the cursor was at the bottom, the text scrolls
              up  one line.  Hitting <Down> arrow in a web browser window, the
              web page scrolls up a small amount.  Or scrolling with a scroll-
              bar or mouse wheel.

              Shorter aliases:  -scr [mode]  and -noscr

              This  scheme  will  not  always detect scrolls, but when it does
              there is a nice speedup from using  the  VNC  CopyRect  encoding
              (see  -wirecopyrect).   The  speedup  is both in reduced network
              traffic and reduced X framebuffer polling/copying.  On the other
              hand, it may induce undesired transients (e.g. a terminal cursor
              being scrolled up when it should not be) or other  painting  er-
              rors  (window  tearing,  bunching-up, etc).  These are automati-
              cally repaired in a short period of time.  If this is  unaccept-
              able disable the feature with -noscrollcopyrect.

              Screen  clearing  kludges:  for testing at least, there are some
              "magic key sequences" (must be done in less than  1  second)  to
              aid  repairing  painting errors that may be seen when using this
              mode:

              3 Alt_L's   in a row: resend whole screen, 4 Alt_L's   in a row:
              reread and resend whole screen, 3 Super_L's in a row: mark whole
              screen for polling, 4 Super_L's in a row: reset RECORD  context,
              5 Super_L's in a row: try to push a black screen

              note:  Alt_L is the Left "Alt" key (a single key) Super_L is the
              Left "Super" key (Windows flag).  Both  of  these  are  modifier
              keys,  and  so  should  not  generate characters when pressed by
              themselves.  Also, your VNC viewer may have its own refresh hot-
              key or button.

              "mode"  can  be "never" (same as -noscrollcopyrect) to never try
              the copyrect, "keys" means to try it in response  to  keystrokes
              only,  "mouse" means to try it in response to mouse events only,
              "always" means to do both. Default: "always"

              Note: there can be painting errors or slow response  when  using
              -scale  so  you  may  want  to  disable  CopyRect  in  this case
              "-scrollcopyrect never" on the command line  or  by  remote-con-
              trol.  Or you can also use the "-scale xxx:nocr" scale option.

       -scr_area n

              Set  the minimum area in pixels for a rectangle to be considered
              for the -scrollcopyrect detection  scheme.   This  is  to  avoid
              wasting the effort on small rectangles that would be quickly up-
              dated the normal way.  E.g. suppose an app updated the  position
              of  its  skinny scrollbar first and then shifted the large panel
              it controlled.  We want to be sure to skip the  small  scrollbar
              and get the large panel. Default: 60000

       -scr_skip list

              Skip  scroll detection for applications matching the comma sepa-
              rated list of strings  in  list.   Some  applications  implement
              their  scrolling  in strange ways where the XCopyArea, etc, also
              applies to invisible portions of  the  window:  if  we  CopyRect
              those  areas  it  looks awful during the scroll and there may be
              painting errors left after the scroll.  Soffice.bin is the worst
              known offender.

              Use  "##"  to  denote  the  start of the application class (e.g.
              "##XTerm") and "++" to denote the start of the  application  in-
              stance  name  (e.g. "++xterm").  The string your list is matched
              against is of the form "^^WM_NAME##Class++Instance<same-for-any-
              subwindows>"  The  "xlsclients  -la"  command  will provide this
              info.

              If a pattern is prefixed with "KEY:" it  only  applies  to  Key-
              stroke  generated  scrolls  (e.g.  Up arrow).  If it is prefixed
              with "MOUSE:" it only applies to  Mouse  induced  scrolls  (e.g.
              dragging  on  a  scrollbar).   Default:  ##Soffice.bin,##StarOf-
              fice,##OpenOffice

       -scr_inc list

              Opposite of -scr_skip: this list is consulted first and if there
              is  a  match the window will be monitored via RECORD for scrolls
              irrespective of -scr_skip.  Use -scr_skip '*' to  skip  anything
              that  does not match your -scr_inc.  Use -scr_inc '*' to include
              everything.

       -scr_keys list

              For keystroke scroll detection, only apply the RECORD heuristics
              to  the  comma  separated list of keysyms in list.  You may find
              the RECORD overhead for every one of  your  keystrokes  disrupts
              typing  too  much,  but you don't want to turn it off completely
              with "-scr mouse" and -scr_parms does not work or is too confus-
              ing.

              The  listed  keysyms  can  be numeric or the keysym names in the
              <X11/keysymdef.h> header file or from the xev(1) program.  Exam-
              ple: "-scr_keys Up,Down,Return".  One probably wants to have ap-
              plication specific lists (e.g. for terminals, etc) but  that  is
              too icky to think about for now...

              If  list  begins  with the "-" character the list is taken as an
              exclude list: all keysyms except those list will be  considered.
              The  special  string  "builtin"  expands  to an internal list of
              keysyms that are likely to cause scrolls.  BTW, by default modi-
              fier  keys,  Shift_L, Control_R, etc, are skipped since they al-
              most never induce scrolling by themselves.

       -scr_term list

              Yet another cosmetic kludge.  Apply shell/terminal heuristics to
              applications   matching   comma  separated  list  (same  as  for
              -scr_skip/-scr_inc).  For example an  annoying  transient  under
              scroll  detection  is  if you hit Enter in a terminal shell with
              full text window, the solid text cursor block will  be  scrolled
              up.   So  for a short time there are two (or more) block cursors
              on the screen.  There are similar  scenarios,  (e.g.  an  output
              line is duplicated).

              These  transients are induced by the approximation of scroll de-
              tection (e.g. it detects the scroll, but not the fact  that  the
              block cursor was cleared just before the scroll).  In nearly all
              cases these transient errors are repaired when the true X frame-
              buffer  is  consulted  by the normal polling.  But they are dis-
              tracting, so what this option provides is extra  "padding"  near
              the  bottom  of  the terminal window: a few extra lines near the
              bottom will not be scrolled, but rather updated from the  actual
              X  framebuffer.   This  usually  reduces the annoying artifacts.
              Use "none" to disable.  Default: "term"

       -scr_keyrepeat lo-hi

              If a key is held down (or otherwise repeats  rapidly)  and  this
              induces  a rapid sequence of scrolls (e.g. holding down an Arrow
              key) the "scrollcopyrect" detection and overhead may not be able
              to  keep up.  A time per single scroll estimate is performed and
              if that estimate predicts a sustainable scrollrate of  keys  per
              second  between  "lo"  and  "hi" then repeated keys will be DIS-
              CARDED to maintain the scrollrate. For example your key  autore-
              peat  may  be  25  keys/sec, but for a large window or slow link
              only 8 scrolls per second can be sustained, then roughly  2  out
              of  every  3 repeated keys will be discarded during this period.
              Default: "4-20"

       -scr_parms string

              Set various parameters for the scrollcopyrect mode.  The  format
              is similar to that for -wireframe and packed with lots of param-
              eters:

              Format:         T+B+L+R,t1+t2+t3,s1+s2+s3+s4+s5         Default:
              0+64+32+32,0.02+0.10+0.9,0.03+0.06+0.5+0.1+5.0

              If  you  leave nothing between commas: ",," the default value is
              used.  If you don't specify enough commas, the trailing  parame-
              ters are set to their defaults.

              "T+B+L+R"  indicates  four  integers for how close in pixels the
              pointer has to be from the Top, Bottom, Left, or Right edges  of
              the  window  to consider scrollcopyrect.  If -wireframe overlaps
              it takes precedence.  This is a speedup  to  quickly  exclude  a
              window  from  being  watched for scrollcopyrect: set them all to
              zero to not try the speedup (things  like  selecting  text  will
              likely be slower).

              "t1+t2+t3"  specify  three  floating point times in seconds that
              apply to scrollcopyrect detection with *Keystroke* input: t1  is
              how long to wait after a key is pressed for the first scroll, t2
              is how long to keep looking after a Keystroke  scroll  for  more
              scrolls.   t3  is  how  frequently  to try to update surrounding
              scrollbars outside of the scrolling area (0.0 to disable)

              "s1+s2+s3+s4+s5" specify five floating point  times  in  seconds
              that apply to scrollcopyrect detection with *Mouse* input: s1 is
              how long to wait after a mouse button is pressed for  the  first
              scroll,  s2  is  how long to keep waiting for additional scrolls
              after the first Mouse scroll was detected.  s3 is how frequently
              to try to update surrounding scrollbars outside of the scrolling
              area (0.0 to disable).  s4 is how long to buffer pointer  motion
              (to  try  to get fewer, bigger mouse scrolls). s5 is the maximum
              time to spend just updating the scroll window  without  updating
              the rest of the screen.

       -fixscreen string

              Periodically  "repair"  the  screen based on settings in string.
              Hopefully you won't need this option, it is intended  for  cases
              when  the  -scrollcopyrect  or  -wirecopyrect features leave too
              many painting errors, but it can be used for any scenario.  This
              option  periodically  performs costly operations and so interac-
              tive response may be reduced when it  is  on.   You  can  use  3
              Alt_L's  (the  Left "Alt" key) taps in a row (as described under
              -scrollcopyrect) instead to manually request  a  screen  repaint
              when it is needed.

              string  is  a comma separated list of one or more of the follow-
              ing: "V=t", "C=t", "X=t", and "8=t".  In these "t" stands for  a
              time  in  seconds (it is a floating point even though one should
              usually use values > 2 to avoid wasting resources).  V sets  how
              frequently  the  entire  screen should be sent to viewers (it is
              like the 3 Alt_L's).  C sets how long to wait after  a  CopyRect
              to repaint the full screen.  X sets how frequently to reread the
              full X11 framebuffer from the X server and push it out  to  con-
              nected viewers.  Use of X should be rare, please report a bug if
              you find you need it. 8= applies only for -8to24 mode:  it  sets
              how  often  the  non-default  visual regions of the screen (e.g.
              8bpp  windows)  are  refreshed.    Examples:   -fixscreen   V=10
              -fixscreen C=10

       -debug_scroll

              Turn  on  debugging  info  printout  for  the scroll heuristics.
              "-ds" is an alias.  Specify it multiple times for more output.

       -noxrecord

              Disable any use of the RECORD extension.  This is currently used
              by the -scrollcopyrect scheme and to monitor X server grabs.

       -grab_buster, -nograb_buster

              Some  of the use of the RECORD extension can leave a tiny window
              for XGrabServer deadlock.  This  is  only  if  the  whole-server
              grabbing  application expects mouse or keyboard input before re-
              leasing the grab.  It is usually  a  window  manager  that  does
              this.   x11vnc  takes  care  to avoid the problem, but if caught
              x11vnc will freeze.  Without -grab_buster, the only solution  is
              to go the physical display and give it some input to satisfy the
              grabbing app.  Or manually kill and restart the  window  manager
              if  that  is  feasible.   With  -grab_buster, x11vnc will fork a
              helper thread and if x11vnc appears to be stuck in a grab  after
              a  period  of time (20-30 sec) then it will inject some user in-
              put: button clicks, Escape, mouse motion, etc to  try  to  break
              the  grab.  If you experience a lot of grab deadlock, please re-
              port a bug.

       -debug_grabs

              Turn on debugging info printout with  respect  to  XGrabServer()
              deadlock for -scrollcopyrect__mode_.

       -debug_sel

              Turn  on  debugging info printout with respect to PRIMARY, CLIP-
              BOARD, and CUTBUFFER0 selections.

       -pointer_mode n

              Various pointer motion update schemes. "-pm" is an  alias.   The
              problem is pointer motion can cause rapid changes on the screen:
              consider the rapid changes when you drag a large  window  around
              opaquely.   Neither  x11vnc's screen polling and vnc compression
              routines nor the bandwidth to the vncviewers can keep  up  these
              rapid  screen changes: everything will bog down when dragging or
              scrolling.  So a scheme has to be used to  "eat"  much  of  that
              pointer  input  before  re-polling  the  screen  and sending out
              framebuffer updates. The mode number n can be 0 to 4 and selects
              one of the schemes described below.

              Note  that the -wireframe and -scrollcopyrect__mode_s complement
              -pointer_mode by detecting (and improving)  certain  periods  of
              "rapid screen change".

              n=0:  does  the same as -nodragging. (all screen polling is sus-
              pended if a mouse button is pressed.)

              n=1: was the original scheme used to about Jan  2004:  it  basi-
              cally  just  skips -input_skip keyboard or pointer events before
              repolling the screen.

              n=2 is an improved scheme: by watching the current rate of input
              events  it  tries to detect if it should try to "eat" additional
              pointer events before continuing.

              n=3 is basically a dynamic -nodragging mode: it detects when the
              mouse motion has paused and then refreshes the display.

              n=4  attempts  to  measures network rates and latency, the video
              card read rate, and how many tiles  have  been  changed  on  the
              screen.   From  this,  it  aggressively  tries  to  push  screen
              "frames" when it decides it has enough resources to do so.   NOT
              FINISHED.

              The  default  n  is  2.  Note  that modes 2, 3, 4 will skip -in-
              put_skip keyboard events (but it will not count pointer events).
              Also  note  that  these modes are not available in -threads mode
              which has its own pointer event handling mechanism.

              To try out the different pointer modes to see  which  one  gives
              the  best  response  for your usage, it is convenient to use the
              remote control function, for example "x11vnc  -R  pm:4"  or  the
              tcl/tk gui (Tuning -> pointer_mode -> n).

       -input_skip n

              For  the  pointer handling when non-threaded: try to read n user
              input events before scanning display. n <  0  means  to  act  as
              though there is always user input.  Default: 10

       -allinput

              Have  x11vnc  read and process all available client input before
              proceeding.

       -input_eagerly

              Similar to -allinput but use the  handleEventsEagerly  mechanism
              built into LibVNCServer.

       -multiptr

              Enable  support  for  per-client input devices. Each client will
              get its own cursor and keyboard focus.

       -speeds rd,bw,lat

              x11vnc tries to estimate some speed parameters that are used  to
              optimize  scheduling (e.g. -pointer_mode 4, -wireframe, -scroll-
              copyrect) and other things.  Use the -speeds option to set these
              manually.   The  triple  rd,bw,lat corresponds to video h/w read
              rate in MB/sec, network bandwidth to clients in KB/sec, and net-
              work  latency  to  clients  in milliseconds, respectively.  If a
              value is left blank, e.g. "-speeds ,100,15", then  the  internal
              scheme is used to estimate the empty value(s).

              Typical  PC  video cards have read rates of 5-10 MB/sec.  If the
              framebuffer is in main memory instead of video h/w (e.g. SunRay,
              shadowfb, dummy driver, Xvfb), the read rate may be much faster.
              "x11perf -getimage500" can be used to get a lower bound  (remem-
              ber to factor in the bytes per pixel).  It is up to you to esti-
              mate the network bandwidth and latency to clients.  For the  la-
              tency the ping(1) command can be used.

              For  convenience  there are some aliases provided, e.g. "-speeds
              modem".   The  aliases  are:  "modem"  for  6,4,200;  "dsl"  for
              6,100,50; and "lan" for 6,5000,1

       -wmdt string

              For  some  features, e.g. -wireframe and -scrollcopyrect, x11vnc
              has to work around issues for certain window managers  or  desk-
              tops  (currently  kde  and  xfce).  By default it tries to guess
              which one, but it can guess incorrectly.  Use this option to in-
              dicate  which  wm/dt.   string  can  be  "gnome",  "kde", "cde",
              "xfce", or "root" (classic X wm).  Anything else is  interpreted
              as "root".

       -debug_pointer

              Print debugging output for every pointer event.

       -debug_keyboard

              Print debugging output for every keyboard event.

       Same as -dp and -dk, respectively.  Use multiple times for more output.

       -defer time

              Time in ms to delay sending updates to connected clients (defer-
              UpdateTime)  Default: 20

       -wait time

              Time in ms to pause between screen polls.  Used to cut  down  on
              load.  Default: 20

       -extra_fbur n

              Perform  extra  FrameBufferUpdateRequests checks to try to be in
              better sync with the client's requests.  What this does is  per-
              form  extra polls of the client socket at critical times (before
              '-defer' and '-wait' calls.)  The default  is  n=1.   Set  to  a
              larger number to insert more checks or set to n=0 to disable.  A
              downside of these extra calls is that more mouse  input  may  be
              processed than desired.

       -wait_ui factor

              Factor  by  which to cut the -wait time if there has been recent
              user input (pointer or keyboard).  Improves  response,  but  in-
              creases  the  load  whenever you are moving the mouse or typing.
              Default: 2.00

       -setdefer n

              When the -wait_ui mechanism cuts down the wait time ms, set  the
              defer  time  to  the same ms value. n=1 to enable, 0 to disable,
              and -1 to set defer to 0 (no delay).  Similarly, 2 and -2  indi-
              cate  'urgent_update'  mode  should  be used to push the updates
              even sooner.  Default: 1

       -nowait_bog

              Do not detect if the screen polling is "bogging down" and  sleep
              more.  Some activities with no user input can slow things down a
              lot: consider a large terminal window with a long build  running
              in  it  continuously  streaming  text output.  By default x11vnc
              will try to detect this (3 screen polls in  a  row  each  longer
              than  0.25  sec with no user input), and sleep up to 1.5 secs to
              let things "catch up".  Use this option to disable  that  detec-
              tion.

       -slow_fb time

              Floating point time in seconds to delay all screen polling.  For
              special purpose usage where a low frame rate is  acceptable  and
              desirable,  but  you want the user input processed at the normal
              rate so you cannot use -wait.

       -xrefresh time

              Floating point time in seconds to indicate how often to  do  the
              equivalent  of xrefresh(1) to force all windows (in the viewable
              area if -id, -sid, or -clip is used) to repaint themselves.  Use
              this only if applications misbehave by not repainting themselves
              properly.  See also -noxdamage.

       -nap, -nonap

              Monitor activity and if it  is  low  take  longer  naps  between
              screen  polls  to really cut down load when idle.  Default: take
              naps

       -sb time

              Time in seconds after NO activity (e.g. screen blank) to  really
              throttle  down the screen polls (i.e. sleep for about 1.5 secs).
              Use 0 to disable.  Default: 60 Set the env. var.  X11VNC_SB_FAC-
              TOR to scale it.

       -readtimeout n

              Set  LibVNCServer  rfbMaxClientWait  to n seconds. On slow links
              that take a long time to paint the first screen LibVNCServer may
              hit the timeout and drop the connection.  Default: 20 seconds.

       -ping n

              Send  a  1x1  framebuffer  update to all clients every n seconds
              (e.g. to try to keep a network connection alive)

       -nofbpm, -fbpm

              If the system supports the FBPM (Frame Buffer Power  Management)
              extension  (i.e.  some  Sun systems), then prevent the video h/w
              from going into a reduced power state when VNC clients are  con-
              nected.

              FBPM  capable video h/w save energy when the workstation is idle
              by going into low power states (similar to DPMS  for  monitors).
              This interferes with x11vnc's polling of the framebuffer data.

              "-nofbpm"  means  prevent  FBPM  low  power  states whenever VNC
              clients are connected, while "-fbpm" means to  not  monitor  the
              FBPM  state at all.  See the xset(1) manpage for details.  -nof-
              bpm is basically the same as running "xset fbpm force on"  peri-
              odically.  Default: -fbpm

       -nodpms, -dpms

              If  the  system supports the DPMS (Display Power Management Sig-
              naling) extension, then prevent the monitor from  going  into  a
              reduced power state when VNC clients are connected.

              DPMS  reduced power monitor states are a good thing and you nor-
              mally want the power down to take place (usually x11vnc  has  no
              problem exporting the display in this state).  You probably only
              want to use "-nodpms" to work around problems with Screen Savers
              kicking  on  in  DPMS  low power states.  There is known problem
              with kdesktop_lock on KDE where the screen saver  keeps  kicking
              in  every time user input stops for a second or two.  Specifying
              "-nodpms" works around it.

              "-nodpms" means prevent  DPMS  low  power  states  whenever  VNC
              clients  are  connected,  while "-dpms" means to not monitor the
              DPMS state  at  all.   See  the  xset(1)  manpage  for  details.
              -nodpms  is  basically  the same as running "xset dpms force on"
              periodically.  Default: -dpms

       -forcedpms

              If the system supports the DPMS (Display Power  Management  Sig-
              naling) extension, then try to keep the monitor in a powered off
              state.  This is to prevent nosey people at the physical  display
              from  viewing what is on the screen.  Be sure to lock the screen
              before disconnecting.

              This method is far from bullet proof, e.g. suppose  someone  at-
              taches a non-DPMS monitor, or loads the machine so that there is
              a gap of time before x11vnc restores the powered off state?   On
              many  machines  if he floods it with keyboard and mouse input he
              can see flashes of what is on the screen  before  the  DPMS  off
              state  is  reestablished.  For this to work securely there would
              need to be support in the X server to  do  this  exactly  rather
              than approximately with DPMS.

       -clientdpms

              As -forcedpms but only when VNC clients are connected.

       -noserverdpms

              The  UltraVNC  ServerInput  extension is supported.  This allows
              the VNC viewer to click a button  that  will  cause  the  server
              (x11vnc) to try to disable keyboard and mouse input at the phys-
              ical display and put the monitor in dpms powered off state.  Use
              this option to skip powering off the monitor.

       -noultraext

              Disable  the  following  UltraVNC  extensions:  SingleWindow and
              ServerInput.  The others managed by LibVNCServer (textchat,  1/n
              scaling, rfbEncodingUltra) are not.

       -chatwindow

              Place  a  local  UltraVNC  chat  window  on the X11 display that
              x11vnc is polling.  That way the person on the  VNC  viewer-side
              can  chat  with  the  person  at the physical X11 console. (e.g.
              helpdesk w/o telephone)

              For this to work the SSVNC package  (version  1.0.21  or  later)
              MUST  BE  installed  on  the  system  where  x11vnc runs and the
              'ssvnc' command must be available in $PATH.  The ssvncviewer  is
              used   as   a   chat   window   helper.    See  http://www.karl-
              runge.com/x11vnc/ssvnc.html

              This option implies '-rfbversion 3.6' so as  to  trick  UltraVNC
              viewers,  otherwise they assume chat is not available.  To spec-
              ify a different rfbversion, place it after the  -chatwindow  op-
              tion on the cmdline.

              See  also  the  remote  control  'chaton' and 'chatoff' actions.
              These can also be set from the tkx11vnc GUI.

       -noxdamage

              Do not use the X DAMAGE extension to detect framebuffer  changes
              even  if  it  is  available.  Use -xdamage if your default is to
              have it off.

              x11vnc's use of the DAMAGE extension: 1)  significantly  reduces
              the  load  when  the screen is not changing much, and 2) detects
              changed areas (small ones by default) more quickly.

              Currently the DAMAGE extension is overly conservative and  often
              reports large areas (e.g. a whole terminal or browser window) as
              damaged even though the actual changed region  is  much  smaller
              (sometimes just a few pixels).  So heuristics were introduced to
              skip large areas and use the damage rectangles only  as  "hints"
              for  the traditional scanline polling.  The following tuning pa-
              rameters are introduced to adjust this behavior:

       -xd_area A

              Set the largest DAMAGE rectangle area  A  (in  pixels:  width  *
              height)  to trust as truly damaged: the rectangle will be copied
              from the framebuffer (slow) no matter  what.   Set  to  zero  to
              trust *all* rectangles. Default: 20000

       -xd_mem f

              Set  how  long  DAMAGE rectangles should be "remembered", f is a
              floating point number and is in units of the scanline repeat cy-
              cle  time  (32  iterations).   The  default (1.0) should give no
              painting problems. Increase it if there are problems or decrease
              it to live on the edge (perhaps useful on a slow machine).

       -sigpipe string

              Broken  pipe  (SIGPIPE)  handling.   string  can  be "ignore" or
              "exit".  For "ignore" LibVNCServer will handle the  abrupt  loss
              of  a  client  and  continue, for "exit" x11vnc will cleanup and
              exit at the 1st broken connection.

              This option is not really needed since LibVNCServer is doing the
              correct thing now for quite some time.  However, for convenience
              you can use it to  ignore  other  signals,  e.g.  "-sigpipe  ig-
              nore:HUP,INT,TERM" in case that would be useful for some sort of
              application.  You can also put "exit:.." in  the  list  to  have
              x11vnc  cleanup  on  the  listed signals. "-sig" is an alias for
              this option if you don't like  the  'pipe'.  Example:  -sig  ig-
              nore:INT,TERM,exit:USR1

       -threads, -nothreads

              Whether  or  not to use the threaded LibVNCServer algorithm [rf-
              bRunEventLoop] if libpthread is available.   In  this  mode  new
              threads (one for input and one for output) are created to handle
              each new client.  Default: -nothreads.

              Thread stability is much improved in version 0.9.8.

              Multiple clients in threaded mode should be stable for the  ZRLE
              encoding  on  all  platforms.   The Tight and Zlib encodings are
              currently only stable on Linux for  multiple  clients.   Compile
              with  -DTLS=__thread  if your OS and compiler and linker support
              it.

              For resizes (randr, etc.) set this env. var. to  the  number  of
              milliseconds  to  sleep:  X11VNC_THREADS_NEW_FB_SLEEP at various
              places in the do_new_fb() action.  This is to let various activ-
              ities settle.  Default is about 500ms.

              Multiple clients in threaded mode could yield better performance
              for 'class-room' broadcasting usage; also in -appshare broadcast
              mode.  See also the -reflect option.

       -fs f

              If  the  fraction  of changed tiles in a poll is greater than f,
              the whole screen is updated.  Default: 0.75

       -gaps n

              Heuristic to fill in gaps in rows or cols of n  or  less  tiles.
              Used to improve text paging.  Default: 4

       -grow n

              Heuristic  to grow islands of changed tiles n or wider by check-
              ing the tile near the boundary.  Default: 3

       -fuzz n

              Tolerance in pixels to mark a tiles edges as changed.   Default:
              2

       -debug_tiles

              Print debugging output for tiles, fb updates, etc.

       -snapfb

              Instead  of  polling the X display framebuffer (fb) for changes,
              periodically copy all of X display fb into main memory and exam-
              ine that copy for changes.  (This setting also applies for non-X
              -rawfb modes).  Under some circumstances this will  improve  in-
              teractive  response,  or at least make things look smoother, but
              in others (most!) it will make the response worse.  If the video
              h/w  fb  is such that reading small tiles is very slow this mode
              could help.  To keep the "framerate" up the screen  size  x  bpp
              cannot  be  too  large.  Note that this mode is very wasteful of
              memory I/O resources (it makes full screen copies even if  noth-
              ing  changes).   It may be of use in video capture-like applica-
              tions, webcams, or where window tearing is a problem.

       -rawfb string

              Instead of polling  X,  poll  the  memory  object  specified  in
              string.

              For   file   polling,   to   memory  map  mmap(2)  a  file  use:
              "map:/path/to/a/file@WxHxB", with framebuffer Width, Height, and
              Bits per pixel.  "mmap:..." is the same.

              If  there  is  trouble  with  mmap,  use "file:/..."  for slower
              lseek(2) based reading.

              Use "snap:..." to imply -snapfb  mode  and  the  "file:"  access
              (this  is for unseekable devices that only provide the fb all at
              once, e.g. a video camera provides the whole frame).

              For shared memory segments string is of the form:  "shm:N@WxHxB"
              which specifies a shmid N and with WxHxB as above.  See shmat(1)
              and ipcs(1)

              If you do not supply a type "map" is assumed if the file  exists
              (see the next paragraphs for some exceptions to this.)

              If  string is "setup:cmd", then the command "cmd" is run and the
              first line from it is read and used as string.  This allows ini-
              tializing  the  device,  determining WxHxB, etc. These are often
              done as root so take care.

              If the string begins with "video", see the  VIDEO4LINUX  discus-
              sion  below  where  the  device may be queried for (and possibly
              set) the framebuffer parameters.

              If the string begins with "console", "/dev/fb", "fb",  or  "vt",
              see the LINUX CONSOLE discussion below where the framebuffer de-
              vice is opened and keystrokes (and possibly  mouse  events)  are
              inserted into the console.

              If the string begins with "vnc", see the VNC HOST discussion be-
              low where the framebuffer is taken as that of another remote VNC
              server.

              Optional  suffixes  are ":R/G/B" and "+O" to specify red, green,
              and blue masks (in hex) and an offset into  the  memory  object.
              If  the  masks are not provided x11vnc guesses them based on the
              bpp (if the colors look wrong, you need to provide the masks.)

              Another optional suffix is the Bytes  Per  Line  which  in  some
              cases   is   not   WxB/8.    Specify   it   as   WxHxB-BPL  e.g.
              800x600x16-2048.  This could be a normal width 1024 at 16bpp fb,
              but only width 800 shows up.

              So the full format is: mode:file@WxHxB:R/G/B+O-BPL

              Examples:

              -rawfb shm:210337933@800x600x32:ff/ff00/ff0000

              -rawfb map:/dev/fb0@1024x768x32

              -rawfb map:/tmp/Xvfb_screen0@640x480x8+3232

              -rawfb file:/tmp/my.pnm@250x200x24+37

              -rawfb             file:/dev/urandom@128x128x8            -rawfb
              snap:/dev/video0@320x240x24 -24to32 -rawfb video0  -rawfb  video
              -pipeinput VID -rawfb console -rawfb vt2 -rawfb vnc:somehost:0

              (see ipcs(1) and fbset(1) for the first two examples)

              In  general  all  user  input  is  discarded by default (see the
              -pipeinput option for how to use a helper  program  to  insert).
              Most  of  the  X11 (screen, keyboard, mouse) options do not make
              sense and many will cause this mode to crash,  so  please  think
              twice before setting or changing them in a running x11vnc.

              If  you DO NOT want x11vnc to close the X DISPLAY in rawfb mode,
              prepend a "+" e.g. +file:/dev/fb0...  Keeping the  display  open
              enables  the default remote-control channel, which could be use-
              ful.  Alternatively, if you specify -noviewonly, then the  mouse
              and  keyboard  input are STILL sent to the X display, this usage
              should be very rare, i.e. doing something strange with /dev/fb0.

              If the device is not "seekable" (e.g. webcam) try reading it all
              at  once in full snaps via the "snap:" mode (note: this is a re-
              source hog).  If you are using file:  or  map:  AND  the  device
              needs  to be reopened for *every* snapfb snapshot, set the envi-
              ronment variable: SNAPFB_RAWFB_RESET=1 as well.

              If you want x11vnc to dynamically transform  a  24bpp  rawfb  to
              32bpp  (note  that  this will be slower) also supply the -24to32
              option.  This would be useful for, say, a video camera that  de-
              livers  the pixel data as 24bpp packed RGB.  This is the default
              under "video" mode if the bpp is 24.

              Normally the bits per pixel, B, is 8, 16, or 32 (or rarely  24),
              however  there is also some support for B < 8 (e.g. old graphics
              displays 4 bpp or 1 bpp).  In this case you certainly must  sup-
              ply  the  masks as well: WxHxB:R/G/B.  The pixels will be padded
              out to 8 bpp using depth 8 truecolor.  The scheme currently does
              not  work with snap fb (ask if interested.) B=1 monochrome exam-
              ple: file:/dev/urandom@128x128x1:1/1/1 Some other like this  are
              128x128x2:3/3/3 128x128x4:7/7/7

              For B < 8 framebuffers you can also set the env. var RAWFB_CGA=1
              to try a CGA mapping for B=4 (e.g. linux vga16fb driver.)   Note
              with  low bpp and/or resolution VGA and VGA16 modes on the Linux
              console one's attempt to export them via  x11vnc  can  often  be
              thwarted due to special color palettes, pixel packings, and even
              video painting buffering.  OTOH, often  experimenting  with  the
              RGB masks can yield something recognizable.

              VIDEO4LINUX:  on  Linux some attempt is made to handle video de-
              vices (webcams or TV tuners) automatically.  The idea is the Wx-
              HxB  will be extracted from the device itself.  So if you do not
              supply "@WxHxB...  parameters x11vnc will try to determine them.
              It first tries the v4l API if that support has been compiled in.
              Otherwise it will run the v4l- info(1) external program if it is
              available.

              The  simplest  examples  are  "-rawfb video" and "-rawfb video1"
              which imply the device file /dev/video and /dev/video1,  respec-
              tively.   You can also supply the /dev if you like, e.g. "-rawfb
              /dev/video0"

              Since the video capture device framebuffer usually changes  con-
              tinuously  (e.g.  brightness  fluctuations), you may want to use
              the -wait, -slow_fb, or -defer options to lower the  "framerate"
              to cut down on network VNC traffic.

              A more sophisticated video device scheme allows initializing the
              device's settings using:

              -rawfb video:<settings>

              The prefix could also be, as above, e.g.  "video1:"  to  specify
              the  device  file.   The  v4l  API must be available for this to
              work.  Otherwise, you will need to try to initialize the  device
              with  an  external  program, e.g. xawtv, spcaview, and hope they
              persist when x11vnc re-opens the device.

              <settings> is a comma separated list of  key=value  pairs.   The
              device's brightness, color, contrast, and hue can be set to per-
              centages, e.g. br=80,co=50,cn=44,hu=60.

              The device filename can be set too if needed  (if  it  does  not
              start with "video"), e.g. fn=/dev/qcam.

              The  width,  height  and  bpp of the framebuffer can be set via,
              e.g., w=160,h=120,bpp=16.

              Related to the bpp above, the pixel format can be  set  via  the
              fmt=XXX,  where  XXX can be one of: GREY, HI240, RGB555, RGB565,
              RGB24, and RGB32 (with bpp 8, 8, 16,  16,  24,  and  32  respec-
              tively).  See http://www.linuxtv.org for more info (V4L api).

              For  TV/rf  tuner  cards one can set the tuning mode via tun=XXX
              where XXX can be one of PAL, NTSC, SECAM, or AUTO.

              One can switch the input channel by the inp=XXX  setting,  where
              XXX is the name of the input channel (Television, Composite1, S-
              Video, etc).  Use the name that is in the information about  the
              device that is printed at startup.

              For  input channels with tuners (e.g. Television) one can change
              which station is selected by the sta=XXX setting.   XXX  is  the
              station  number.   Currently  only  the ntsc-cable-us (US cable)
              channels are built into x11vnc.  See the -freqtab  option  below
              to supply one from xawtv. If XXX is greater than 500, then it is
              interpreted as a raw frequency in KHz.

              Example:

              -rawfb video:br=80,w=320,h=240,fmt=RGB32,tun=NTSC,sta=47

              one might need to add inp=Television too for the  input  channel
              to be TV if the card doesn't come up by default in that one.

              Note  that not all video capture devices will support all of the
              above settings.

              See the -pipeinput VID option below for a  way  to  control  the
              settings  through the VNC Viewer via keystrokes.  As a shortcut,
              if  the  string  begins  "Video.."  instead  of  "video.."  then
              -pipeinput VID is implied.

              As  above,  if  you  specify  a "@WxHxB..." after the <settings>
              string they are used verbatim: the device is not queried for the
              current values.  Otherwise the device will be queried.

              LINUX  CONSOLE:   The  following describes some ways to view and
              possibly interact with the Linux text/graphics console (i.e. not
              X11 XFree86/Xorg)

              Note: If the LibVNCServer LinuxVNC program is on your system you
              may want to use that instead of the following method because  it
              will  be faster and more accurate for the Linux text console and
              includes mouse support.  There is, however, the  basic  LinuxVNC
              functionality  in  x11vnc  if you replace "console" with "vt" in
              the examples below.

              If the rawfb string begins with "console" the framebuffer device
              /dev/fb0  is  opened and /dev/tty0 is opened too.  The latter is
              used to inject keystrokes (not all are supported, but the  basic
              ones  are).   You will need to be root to inject keystrokes, but
              not necessarily to open /dev/fb0.  /dev/tty0 refers to  the  ac-
              tive  VT,  to indicate one explicitly, use, e.g., "console2" for
              /dev/tty2, etc. by indicating the specific VT number.

              For the Linux framebuffer device, /dev/fb0, (fb1, etc) to be en-
              abled  the  appropriate  kernel  drivers  must  be loaded.  E.g.
              vesafb or  vga16fb  and  also  by  setting  the  boot  parameter
              vga=0x301  (or  0x314,  0x317, etc.)  (The vga=... method is the
              preferred way; set your machines up that way.)  Otherwise  there
              will  be  a  'No  such device' error.  You can also load a Linux
              framebuffer driver specific to your make of video card for  more
              functionality.   Once  the machine is booted one can often 'mod-
              probe' the fb driver as root to obtain a framebuffer device.

              If you cannot get /dev/fb0 working on Linux, try using the  Lin-
              uxVNC  emulation  mode by "-rawfb vtN" where N = 1, ... 6 is the
              Linux Virtual Terminal (aka virtual console) you wish  to  view,
              e.g.  "-rawfb vt2".  Unlike /dev/fb mode, it need not be the ac-
              tive Virtual Terminal.  Note that this mode can only  show  text
              and not graphics.  x11vnc polls the text in /dev/vcsaN

              Set the env. var. RAWFB_VCSA_BW=1 to disable colors in the "vtN"
              mode (i.e. black and white only.)  If you do not prefer the  de-
              fault 16bpp set RAWFB_VCSA_BPP to 8 or 32.  If you need to tweak
              the rawfb parameters by using the 'console_guess' string printed
              at startup, be sure to indicate the snap: method.

              uinput:  If the Linux version appears to be 2.6 or later and the
              "uinput" module appears to be present  (modprobe  uinput),  then
              the uinput method will be used instead of /dev/ttyN.  uinput al-
              lows insertion of BOTH keystrokes and mouse input and so it pre-
              ferred when accessing graphical (e.g. QT-embedded) linux console
              apps.  It also provides more accurate keystroke insertion.   See
              -pipeinput  UINPUT  below for more information on this mode; you
              will have to use -pipeinput if you want to tweak any UINPUT  pa-
              rameters.   You  may  also  want to also use the -nodragging and
              -cursor none options.  Use "console0", etc  or  -pipeinput  CON-
              SOLE to force the /dev/ttyN method.

              Note you can change the Linux VT remotely using the chvt(1) com-
              mand to make the one you want be the active one (e.g. 'chvt 3').
              Sometimes  switching  out  and  back  corrects the framebuffer's
              graphics state.  For the "-rawfb vtN" mode there is no  need  to
              switch the VT's.

              To skip input injecting entirely use "consolex" or "vtx".

              The  string  "/dev/fb0"  (1,  etc.) can be used instead of "con-
              sole".  This can be used to specify a different framebuffer  de-
              vice,  e.g. /dev/fb1.  As a shortcut the "/dev/" can be dropped.
              If the name is something nonstandard, use "console:/dev/foofb"

              If you do not want x11vnc to guess the framebuffer's  WxHxB  and
              masks automatically (sometimes the kernel gives incorrect infor-
              mation), specify them with a @WxHxB (and optional :R/G/B  masks)
              at the end of the string.

              Examples: -rawfb console -rawfb /dev/fb0           (same) -rawfb
              console3              (force    /dev/tty3)    -rawfb    consolex
              (no  keystrokes or mouse) -rawfb console:/dev/nonstd -rawfb con-
              sole      -pipeinput      UINPUT:accel=4.0      -rawfb       vt3
              (/dev/tty3 w/o /dev/fb0)

              VNC  HOST: if the -rawfb string is of the form "vnc:host:N" then
              the VNC display "N" on the remote VNC server "host" is connected
              to  (i.e.  x11vnc  acts  as a VNC client itself) and that frame-
              buffer is exported.

              This mode is really only of use if you  are  trying  to  improve
              performance  in  the  case  of many (e.g. > 10) simultaneous VNC
              viewers, and you try a divide and conquer scheme to reduce band-
              width  and improve responsiveness.  (However, another user found
              this mode useful to export a demo display through a  slow  link:
              then multiple demo viewers connected to the reflecting x11vnc on
              the fast side of the link, and so avoided all of the demo  view-
              ers going through the slow link.)

              For  example,  if there will be 64 simultaneous VNC viewers this
              can lead to a lot of redundant  VNC  traffic  to  and  from  the
              server  host:N, extra CPU usage, and all viewers response can be
              reduced by having to wait for writes to the  slowest  client  to
              finish.   However,  if you set up 8 reflectors/repeaters started
              with option -rawfb vnc:host:N, then there are only 8 connections
              to  host:N.  Each repeater then handles 8 vnc viewer connections
              thereby spreading the load around.  In classroom  broadcast  us-
              age,  try to put the repeaters on different switches.  This mode
              is the same as -reflect host:N.  Replace "host:N" by "listen" or
              "listen:port" for a reverse connection.

              Overall  performance will not be as good as a single direct con-
              nection because, among other  things,  there  is  an  additional
              level of framebuffer polling and pointer motion can still induce
              many changes per second that must be propagated.   Tip:  if  the
              remote  VNC  is  x11vnc  doing wireframing, or an X display that
              does wireframing that gives much  better  response  than  opaque
              window dragging.  Consider the -nodragging option if the problem
              is severe.

              The env. var. X11VNC_REFLECT_PASSWORD can be set to the password
              needed    to   log   into   the   vnc   host   server,   or   to
              "file:path_to_file" to indicate a file containing  the  password
              as its first line.

              To set the pixel format that x11vnc requests as a VNC CLIENT set
              the env. vars: X11VNC_REFLECT_bitsPerSample  X11VNC_REFLECT_sam-
              plesPerPixel, and X11VNC_REFLECT_bytesPerPixel; the defaults are
              8, 3, 4.  2, 3, 1 would give a low color mode.  See the function
              rfbGetClient() in libvncclient for more info.

              The  VNC  HOST  mode implies -shared.  Use -noshared as a subse-
              quent cmdline option to disable sharing.

       -freqtab file

              For use with "-rawfb video" for TV tuner devices to specify sta-
              tion  frequencies.   Instead of using the built in ntsc-cable-us
              mapping of station number to frequency, use the  data  in  file.
              For  stations  that  are not numeric, e.g. SE20, they are placed
              above the highest numbered station in the order they are  found.
              Example:  "-freqtab /usr/X11R6/share/xawtv/europe-west.list" You
              can make your own freqtab by copying the xawtv format.

       -pipeinput cmd

              This option lets you supply an  external  command  in  cmd  that
              x11vnc  will  pipe  all  of the user input events to in a simple
              format.  In -pipeinput mode by default x11vnc will  not  process
              any  of the user input events.  If you prefix cmd with "tee:" it
              will both send them to the pipe command and process them.  For a
              description  of  the  format run "-pipeinput tee:/bin/cat".  An-
              other prefix is "reopen" which means to reopen pipe if it exits.
              Separate multiple prefixes with commas.

              In  combination  with  -rawfb  one  might  be able to do amusing
              things (e.g. control non-X devices).   To  facilitate  this,  if
              -rawfb is in effect then the value is stored in X11VNC_RAWFB_STR
              for the pipe command to use if it wants. Do 'env | grep  X11VNC'
              for more.

              Built-in pipeinput modes (no external program required):

              If cmd is "VID" and you are using the -rawfb for a video capture
              device, then an internal list of keyboard mappings  is  used  to
              set parameters of the video.  The mappings are:

              "B"  and "b" adjust the brightness up and down.  "H" and "h" ad-
              just the hue.  "C" and "c" adjust the colour.  "N" and  "n"  ad-
              just  the  contrast.  "S" and "s" adjust the size of the capture
              screen.  "I" and "i" cycle through input channels.  Up and  Down
              arrows  adjust  the  station  (if  a tuner) F1, F2, ..., F6 will
              switch the video capture pixel format to HI240,  RGB565,  RGB24,
              RGB32,  RGB555, and GREY respectively.  See -rawfb video for de-
              tails.

              If cmd is "CONSOLE" or "CONSOLEn" where n  is  a  Linux  console
              number,  then the linux console keystroke insertion to /dev/ttyN
              (see -rawfb console) is performed.

              If cmd begins with "UINPUT" then the Linux uinput module is used
              to  insert  both keystroke and mouse events to the Linux console
              (see -rawfb above).  This usually is the  /dev/input/uinput  de-
              vice file (you may need to create it with "mknod /dev/input/uin-
              put c 10 223" and insert the module with "modprobe uinput".

              The UINPUT mode currently only does US keyboards  (a  scan  code
              option may be added), and not all keysyms are supported.  But it
              is probably more accurate than the "CONSOLE" method.

              You may want to use the options -cursor none and -nodragging  in
              this mode.

              Additional   tuning   options   may   be   supplied   via:  UIN-
              PUT:opt1,opt2,... (a comma separated list). If an option  begins
              with "/" it is taken as the uinput device file.

              Which  uinput  is injected can be controlled by an option string
              made of the characters "K", "M", and "B"  (see  the  -input  op-
              tion),  e.g.  "KM"  allows  keystroke  and motion but not button
              clicks.

              A UINPUT option of the form: accel=f, or  accel=fx+fy  sets  the
              mouse  motion "acceleration".  This is used to correct raw mouse
              relative motion into  how  much  the  application  cursor  moves
              (x11vnc  has  no control over, or knowledge of how the windowing
              application interprets the raw mouse  motions).   Typically  the
              acceleration  for  an X display is 2 (see xset "m" option).  "f"
              is a floating point number, e.g. 3.0.  Use "fx+fy" if  you  need
              to supply different corrections for x and y.

              Note:  the default acceleration is 2.0 since it seems both X and
              qt-embedded often (but not always) use this value.

              Even with a correct accel setting the mouse  position  will  get
              out  of  sync (probably due to a mouse "threshold" setting where
              the acceleration doe not apply, set xset(1) ).  The  option  re-
              set=N sets the number of ms (default 150) after which the cursor
              is attempted to be reset (by forcing the mouse  to  (0,  0)  via
              small  increments  and  then back out to (x, y) in 1 jump), This
              correction seems to be needed but can cause jerkiness  or  unex-
              pected behavior with menus, etc.  Use reset=0 to disable.

              If  you  set  the  env.  var  X11VNC_UINPUT_THRESHOLDS  then the
              thresh=n mode will be enabled.   It  is  currently  not  working
              well.   If  |dx|  <= thresh and |dy| < thresh no acceleration is
              applied.  Use "thresh=+n" |dx| + |dy| < thresh to  be  used  in-
              stead (X11?)

              Example: -pipeinput UINPUT:accel=4.0 -cursor none

              If  the  uinput  device has an absolute pointer (as opposed to a
              normal mouse that is a relative pointer) you can specify the op-
              tion "abs".  Note that a touchpad on a laptop is an absolute de-
              vice to some degree.  This (usually)  avoids  all  the  problems
              with  mouse  acceleration.   If  x11vnc has trouble deducing the
              size of the device, use "abs=WxH".  Furthermore, if  the  device
              is  a  touchscreen  (assumed  to  have  an absolute pointer) use
              "touch" or "touch=WxH".  For touchscreens, when a  mouse  button
              is pressed, a pressure increase is injected, and when the button
              is released a pressure of zero is injected.

              If touch has been set, use "touch_always=1" to indicate whenever
              the  mouse  moves  with no button pressed, a touch event of zero
              pressure should be sent anyway.  Also use "btn_touch=1" to indi-
              cate  a  BTN_TOUCH keystroke press or release should be sent in-
              stead of a pressure change.  Set "dragskip=n" to skip n  dragged
              mouse  touches (with pressure applied) before injecting one.  To
              indicate the pressure that should be sent when there is a button
              click  for  a  touchscreen device, specify pressure=n, e.g. n=5.
              The default is n=1.

              If a touch screen is being used ("touch" above) and it is having
              its input processed by tslib, you can specify the tslib calibra-
              tion    file     via     tslib_cal=<file>.      For     example,
              tslib_cal=/etc/pointercal.  To get accurate or even usable posi-
              tioning this is required when tslib is in use.

              The Linux uinput mechanism can be bypassed and one can write in-
              put events DIRECTLY to the devices instead.  To do this, specify
              one or  more  of  the  following  for  the  input  classes:  di-
              rect_rel=<device> direct_abs=<device> direct_btn=<device> or di-
              rect_key=<device>.  The <device> file is usually something  like
              /dev/input/event1  but  you can specify any device file or pipe.
              You must specify each one of the above classes even if they cor-
              respond  to  the same device file (rel/abs and btn are often the
              same.)  Look at the file /proc/bus/input/devices to get an  idea
              what  is available and the device filenames.  Note: The /dev/in-
              put/mouse* devices do not seem to work,  use  the  corresponding
              /dev/input/event*  file  instead.   Any input class not directly
              specified as above will be handled via the uinput mechanism.  To
              disable  creating a uinput device (and thereby discarding unhan-
              dled input), specify "nouinput".

              Examples:

              -pipeinput UINPUT:direct_abs=/dev/input/event1

              this was used on a qtmoko Neo freerunner (armel):

              -pipeinput      UINPUT:touch,tslib_cal=/etc/pointercal,      di-
              rect_abs=/dev/input/event1,nouinput,dragskip=4

              (where the long line has been split into two.)

              You  can set the env. var X11VNC_UINPUT_DEBUG=1 or higher to get
              debugging output for UINPUT mode.

       -macnodim

              For the native MacOSX server, disable dimming.

       -macnosleep

              For the native MacOSX server, disable display sleep.

       -macnosaver

              For the native MacOSX server, disable screensaver.

       -macnowait

              For the native MacOSX server, do not wait for the user to switch
              back to his display.

       -macwheel n

              For  the  native  MacOSX  server, set the mouse wheel speed to n
              (default 5).

       -macnoswap

              For the native MacOSX server, do not swap mouse buttons 2 and 3.

       -macnoresize

              For the native MacOSX server, do not resize or reset the  frame-
              buffer  even  if  it  is  detected that the screen resolution or
              depth has changed.

       -maciconanim n

              For the native MacOSX server, set n to the number  of  millisec-
              onds  that  the  window  iconify/deiconify  animation takes.  In
              -ncache mode this value will be used to skip  the  animation  if
              possible. (default 400)

       -macmenu

              For  the  native  MacOSX  server, in -ncache client-side caching
              mode, try to cache pull down menus  (not  perfect  because  they
              have animated fades, etc.)

       -macuskbd

              For  the native MacOSX server, use the original keystroke inser-
              tion code based on a US keyboard.

       -macnoopengl

              For the native MacOSX server, do not use OpenGL for screen  cap-
              ture,  but rather use the original, deprecated raw memory access
              method: addr = CGDisplayBaseAddress().

       -macnorawfb

              For the native MacOSX server, disable  the  raw  memory  address
              screen capture method.

              MACOSX  NOTE: There are some deprecated MacOSX interfaces to in-
              ject keyboard and mouse events and the raw memory access  method
              is  deprecated  as  well  (however,  OpenGL will be preferred if
              available because it is faster.)  One can force  not  using  any
              deprecated  interfaces  at  compile time by setting -DX11VNC_MA-
              COSX_NO_DEPRECATED=1 in CPPFLAGS.  Or to turn them  off  one  by
              one:  -DX11VNC_MACOSX_NO_DEPRECATED_LOCALEVENTS=1,  -DX11VNC_MA-
              COSX_NO_DEPRECATED_POSTEVENTS=1   or   -DX11VNC_MACOSX_NO_DEPRE-
              CATED_FRAMEBUFFER=1  At  run  time, for testing and workarounds,
              one can disable  them  by  using:  -env  X11VNC_MACOSX_NO_DEPRE-
              CATED=1   -env   X11VNC_MACOSX_NO_DEPRECATED_LOCALEVENTS=1  -env
              X11VNC_MACOSX_NO_DEPRECATED_POSTEVENTS=1  or   -env   X11VNC_MA-
              COSX_NO_DEPRECATED_FRAMEBUFFER=1  Note:  When  doing  either  of
              these for the mouse input not everything works  currently,  e.g.
              double  clicks  and  wireframing.   Also,  screen resolution and
              pixel depth changes will not be  automatically  detected  unless
              the deprecated framebuffer interfaces are allowed.

              Conversely,  if  you are compiling on an older machine that does
              not have some of the newer interfaces, you may need  to  specify
              -DX11VNC_MACOSX_NO_CGEVENTCREATESCROLLWHEELEVENT    -DX11VNC_MA-
              COSX_NO_CGEVENTCREATEMOUSEEVENT         or          -DX11VNC_MA-
              COSX_NO_CGEVENTCREATEKEYBOARDEVENT.        Use      -DX11VNC_MA-
              COSX_USE_GETMAINDEVICE to regain the very old QuickDraw GetMain-
              Device() interface (rare...)

       -gui [gui-opts]

              Start up a simple tcl/tk gui based on the remote control options
              -remote/-query described below.  Requires the "wish" program  to
              be  installed  on  the machine.  "gui-opts" is not required: the
              default is to start up both the full gui and x11vnc with the gui
              showing up on the X display in the environment variable DISPLAY.

              "gui-opts"  can  be  a comma separated list of items.  Currently
              there are these types of items: 1) a gui mode, a  2)  gui  "sim-
              plicity",  3)  the  X  display  the  gui should display on, 4) a
              "tray" or "icon" mode, and 5) a gui geometry.

              1) The gui mode can be "start", "conn", or "wait" "start" is the
              default mode above and is not required.  "conn" means do not au-
              tomatically start up x11vnc, but instead just try to connect  to
              an existing x11vnc process.  "wait" means just start the gui and
              nothing else (you will later instruct the gui to start x11vnc or
              connect to an existing one.)

              2)  The  gui simplicity is off by default (a power-user gui with
              all options is presented) To start with something less  daunting
              supply  the  string  "simple" ("ez" is an alias for this).  Once
              the gui is started you can toggle between the two with "Misc  ->
              simple_gui".

              3)  Note  the  possible  confusion regarding the potentially two
              different X displays: x11vnc polls one, but you may want the gui
              to  appear on another.  For example, if you ssh in and x11vnc is
              not running yet you may want the gui to come  back  to  you  via
              your ssh redirected X display (e.g. localhost:10).

              If  you  do  not  specify a gui X display in "gui-opts" then the
              DISPLAY environment variable and -display option are  tried  (in
              that order).  Regarding the x11vnc X display the gui will try to
              communication with, it first tries -display  and  then  DISPLAY.
              For  example, "x11vnc -display :0 -gui otherhost:0", will remote
              control an x11vnc polling :0 and display the gui on  otherhost:0
              The  "tray/icon" mode below reverses this preference, preferring
              to display on the x11vnc display.

              4) When "tray" or "icon" is specified, the gui  presents  itself
              as  a  small  icon  with  behavior typical of a "system tray" or
              "dock applet".  The color of the  icon  indicates  status  (con-
              nected clients) and there is also a balloon status.  Clicking on
              the icon gives a menu from which properties, etc, can be set and
              the  full  gui is available under "Advanced".  To be fully func-
              tional, the gui mode should be "start" (the default).

              Note that tray or icon mode will imply the -forever  x11vnc  op-
              tion (if the x11vnc server is started along with the gui) unless
              -connect or -connect_or_exit has been specified.  So x11vnc (and
              the  tray/icon  gui)  will  wait  for more connections after the
              first client disconnects.  If you want only one  viewer  connec-
              tion include the -once option.

              For  "icon"  the gui just a small standalone window.  For "tray"
              it will attempt to embed itself in the "system tray"  if  possi-
              ble. If "=setpass" is appended then at startup the X11 user will
              be prompted to set the VNC session password.  If =<hexnumber> is
              appended  that  icon  will attempt to embed itself in the window
              given by hexnumber.  Use =noadvanced to disable  the  full  gui.
              (To supply more than one, use "+" sign).  E.g. -gui tray=setpass
              and -gui icon=0x3600028

              Other modes: "full", the default  and  need  not  be  specified.
              "-gui none", do not show a gui, useful to override a ~/.x11vncrc
              setting, etc.

              5) When "geom=+X+Y" is specified, that geometry is passed to the
              gui  toplevel.   This is the icon in icon/tray mode, or the full
              gui otherwise.  You can also  specify  width  and  height,  i.e.
              WxH+X+Y, but it is not recommended.  In "tray" mode the geometry
              is ignored unless the system tray manager does not  seem  to  be
              running.    One   could   imagine  using  something  like  "-gui
              tray,geom=+4000+4000" with a display manager to keep the gui in-
              visible until someone logs in...

              More icon tricks, "icon=minimal" gives an icon just with the VNC
              display number.  You can also set the font with  "iconfont=...".
              The   following   could   be  useful:  "-gui  icon=minimal,icon-
              font=5x8,geom=24x10+0-0"

              General examples of the -gui option: "x11vnc -gui", "x11vnc -gui
              ez"  "x11vnc  -gui  localhost:10",  "x11vnc  -gui  conn,host:0",
              "x11vnc -gui tray,ez" "x11vnc -gui tray=setpass"

              If you do not intend to start x11vnc from the gui (i.e. just re-
              mote control an existing one), then the gui process can run on a
              different machine from the x11vnc server as long  as  X  permis-
              sions, etc. permit communication between the two.

              FONTS: On some systems the tk fonts can be too small, jagged, or
              otherwise unreadable.  There are 4 env vars you can  set  to  be
              the tk font you prefer:

              X11VNC_FONT_BOLD      main   font   for   menus   and   buttons.
              X11VNC_FONT_FIXED  font for fixed width text.

              X11VNC_FONT_BOLD_SMALL  tray icon  font.   X11VNC_FONT_REG_SMALL
              tray icon menu font.

              The last two only apply for the tray icon mode.

              Here are some examples:

              -env      X11VNC_FONT_BOLD='Helvetica     -16     bold'     -env
              X11VNC_FONT_FIXED='Courier -14' -env X11VNC_FONT_REG_SMALL='Hel-
              vetica -12'

              You  can  put  the  lines like the above (without the quotes) in
              your ~/.x11vncrc file to avoid having to  specify  them  on  the
              x11vnc command line.

       -remote command

              Remotely  control  some  aspects  of  an  already running x11vnc
              server.  "-R" and "-r" are aliases for "-remote".  After the re-
              mote  control  command is sent to the running server the 'x11vnc
              -remote ...'  x11vnc command  exits.   You  can  often  use  the
              -query command (see below) to see if the x11vnc server processed
              your -remote command.

              The default  communication  channel  is  that  of  X  properties
              (specifically  X11VNC_REMOTE),  and  so this command must be run
              with correct settings for DISPLAY  and  possibly  XAUTHORITY  to
              connect  to  the  X server and set the property.  Alternatively,
              use the -display and -auth options to set them  to  the  correct
              values.   The running server cannot use the -novncconnect option
              because that disables the communication channel.  See below  for
              alternate channels.

              For example: 'x11vnc -remote stop' (which is the same as 'x11vnc
              -R stop') will close down the x11vnc server.  'x11vnc -R shared'
              will  enable  shared connections, and 'x11vnc -R scale:3/4' will
              rescale the desktop.

              To use a different name for the X11 property (e.g. to have sepa-
              rate  communication  channels  for multiple x11vnc's on the same
              display) set  the  X11VNC_REMOTE  environment  variable  to  the
              string  you  want,  for  example:  -env X11VNC_REMOTE=X11VNC_RE-
              MOTE_12345 Both sides of the channel must use  the  same  unique
              name.

              To  run  a  bunch  of commands in a sequence use something like:
              x11vnc -R 'script:firstcmd;secondcmd;...'

              Use x11vnc -R script:file=/path/to/file to read commands from  a
              file (can be multi-line and use the comment '#' character in the
              normal way.  The ';' separator must still be  used  to  separate
              each command.)

              To  not  try  to contact another x11vnc process and instead just
              run the command (or query) directly, prefix the command with the
              string "DIRECT:"

              The following -remote/-R commands are supported:

              stop             terminate  the server, same as "quit" "exit" or
              "shutdown".

              ping            see if the x11vnc server responds.   return  is:
              ans=ping:<display>

              ping:mystring    as  above, but use your own unique string.  re-
              turn is: ans=ping:mystring:<xdisplay>

              blacken         try to push a black fb  update  to  all  clients
              (due  to  timings  a client could miss it). Same as "zero", also
              "zero:x1,y1,x2,y2" for a rectangle.

              refresh         send the entire fb to all clients.

              reset           recreate the fb, polling memory, etc.

              id:windowid     set -id window to "windowid". empty or "root" to
              go back to root window

              sid:windowid    set -sid window to "windowid"

              id_cmd:cmd        cmds:   raise,  lower,  map,  unmap,  iconify,
              move:dXdY, resize:dWdH, geom:WxH+X+Y. dX dY,  dW,  and  dH  must
              have  a leading "+" or "-" e.g.: move:-30+10 resize:+20+35 also:
              wm_delete,    wm_name:string    and    icon_name:string.    Also
              id_cmd:win=N:cmd

              waitmapped      wait until subwin is mapped.

              nowaitmapped    do not wait until subwin is mapped.

              clip:WxH+X+Y    set -clip mode to "WxH+X+Y"

              flashcmap       enable  -flashcmap mode.

              noflashcmap     disable -flashcmap mode.

              shiftcmap:n     set -shiftcmap to n.

              notruecolor     enable  -notruecolor mode.

              truecolor       disable -notruecolor mode.

              overlay         enable  -overlay mode (if applicable).

              nooverlay       disable -overlay mode.

              overlay_cursor  in -overlay mode, enable cursor drawing.

              overlay_nocursor  disable cursor drawing. same as nooverlay_cur-
              sor.

              8to24           enable  -8to24 mode (if applicable).

              no8to24         disable -8to24 mode.

              8to24_opts:str  set the -8to24 opts to "str".

              24to32          enable  -24to32 mode (if applicable).

              no24to32        disable -24to32 mode.

              visual:vis      set -visual to "vis"

              scale:frac      set -scale to "frac"

              scale_cursor:f  set -scale_cursor to "f"

              viewonly        enable  -viewonly mode.

              noviewonly      disable -viewonly mode.

              shared          enable  -shared mode.

              noshared        disable -shared mode.

              forever         enable  -forever mode.

              noforever       disable -forever mode.

              timeout:n       reset -timeout to n, if there are  currently  no
              clients, exit unless one connects in the next n secs.

              tightfilexfer   enable  filetransfer for NEW clients.

              notightfilexfer disable filetransfer for NEW clients.

              ultrafilexfer   enable  filetransfer for clients.

              noultrafilexfer disable filetransfer for clients.

              rfbversion:n.m  set -rfbversion for new clients.

              http            enable  http client connections.

              nohttp          disable http client connections.

              deny            deny any new connections, same as "lock"

              nodeny          allow new connections, same as "unlock"

              avahi           enable  avahi service advertising.

              noavahi         disable avahi service advertising.

              mdns            enable  avahi service advertising.

              nomdns          disable avahi service advertising.

              zeroconf        enable  avahi service advertising.

              nozeroconf      disable avahi service advertising.

              connect:host     do  reverse connection to host, "host" may be a
              comma separated list of  hosts  or  host:ports.   See  -connect.
              Passwords  required  as  with  fwd  connections.  See X11VNC_RE-
              VERSE_CONNECTION_NO_AUTH=1

              disconnect:host disconnect  any  clients  from  "host"  same  as
              "close:host".   Use host "all" to close all current clients.  If
              you know the client internal  hex  ID,  e.g.  0x3  (returned  by
              "-query clients" and RFB_CLIENT_ID) you can use that too.

              proxy:host:port set reverse connection proxy (empty to disable).

              allowonce:host   For  the next connection only, allow connection
              from "host". In -ssl mode  two  connections  are  allowed  (i.e.
              Fetch Cert) unless X11VNC_NO_SSL_ALLOW_TWICE=1

              allow:hostlist  set -allow list to (comma separated) "hostlist".
              See -allow and -localhost.  Do not use with -allow /path/to/file
              Use  "+host"  to  add a single host, and use "-host" to delete a
              single host

              localhost       enable  -localhost mode

              nolocalhost     disable -localhost mode

              listen:str      set -listen to str, empty to disable.

              noipv6          enable  -noipv6 mode.

              ipv6            disable -noipv6 mode.

              noipv4          enable  -noipv4 mode.

              ipv4            disable -noipv4 mode.

              6               enable  -6 IPv6 listening mode.

              no6             disable -6 IPv6 listening mode.

              lookup          disable -nolookup mode.

              nolookup        enable  -nolookup mode.

              lookup          disable -nolookup mode.

              input:str       set -input to "str", empty to disable.

              grabkbd         enable  -grabkbd mode.

              nograbkbd       disable -grabkbd mode.

              grabptr         enable  -grabptr mode.

              nograbptr       disable -grabptr mode.

              grabalways      enable  -grabalways mode.

              nograbalways    disable -grabalways mode.

              grablocal:n     set -grablocal to n.

              client_input:str set the K, M, B -input on a  per-client  basis.
              select which client as for disconnect, e.g. client_input:host:MB
              or client_input:0x2:K

              accept:cmd      set -accept "cmd" (empty to disable).

              afteraccept:cmd set -afteraccept (empty to disable).

              gone:cmd        set -gone "cmd" (empty to disable).

              noshm           enable  -noshm mode.

              shm             disable -noshm mode (i.e. use shm).

              flipbyteorder   enable -flipbyteorder mode, you may need to  set
              noshm for this to do something.

              noflipbyteorder disable -flipbyteorder mode.

              onetile          enable  -onetile mode. (you may need to set shm
              for this to do something)

              noonetile       disable -onetile mode.

              solid           enable  -solid mode

              nosolid         disable -solid mode.

              solid_color:color set -solid color (and apply it).

              blackout:str    set -blackout "str"  (empty  to  disable).   See
              -blackout  for  the  form of "str" (basically: WxH+X+Y,...)  Use
              "+WxH+X+Y" to append a single rectangle use "-WxH+X+Y" to delete
              one

              xinerama        enable  -xinerama mode. (if applicable)

              noxinerama      disable -xinerama mode.

              xtrap           enable  -xtrap input mode(if applicable)

              noxtrap         disable -xtrap input mode.

              xrandr          enable  -xrandr mode. (if applicable)

              noxrandr        disable -xrandr mode.

              xrandr_mode:mode set the -xrandr mode to "mode".

              rotate:mode     set the -rotate mode to "mode".

              padgeom:WxH     set -padgeom to WxH (empty to disable) If WxH is
              "force" or "do" the padded geometry fb is immediately applied.

              quiet           enable  -quiet mode.

              noquiet         disable -quiet mode.

              modtweak        enable  -modtweak mode.

              nomodtweak      enable  -nomodtweak mode.

              xkb             enable  -xkb modtweak mode.

              noxkb           disable -xkb modtweak mode.

              capslock        enable  -capslock mode.

              nocapslock      disable -capslock mode.

              skip_lockkeys   enable  -skip_lockkeys mode.

              noskip_lockkeys disable -skip_lockkeys mode.

              skip_keycodes:str enable -xkb -skip_keycodes "str".

              sloppy_keys     enable  -sloppy_keys mode.

              nosloppy_keys   disable -sloppy_keys mode.

              skip_dups       enable  -skip_dups mode.

              noskip_dups     disable -skip_dups mode.

              add_keysyms     enable -add_keysyms mode.

              noadd_keysyms   stop adding keysyms. those added will  still  be
              removed at exit.

              clear_mods      enable  -clear_mods mode and clear them.

              noclear_mods    disable -clear_mods mode.

              clear_keys      enable  -clear_keys mode and clear them.

              noclear_keys    disable -clear_keys mode.

              clear_locks     do the clear_locks action.

              clear_all       do the clear_all action.

              keystate        have x11vnc print current keystate.

              remap:str       set -remap "str" (empty to disable).  See -remap
              for the form of "str" (basically: key1-key2,key3-key4,...)   Use
              "+key1-key2"  to append a single keymapping, use "-key1-key2" to
              delete.

              norepeat        enable  -norepeat mode.

              repeat          disable -norepeat mode.

              nofb            enable  -nofb mode.

              fb              disable -nofb mode.

              bell            enable  bell (if supported).

              nobell          disable bell.

              sendbell        ring the bell now.

              nosel           enable  -nosel mode.

              sel             disable -nosel mode.

              noprimary       enable  -noprimary mode.

              primary         disable -noprimary mode.

              nosetprimary    enable  -nosetprimary mode.

              setprimary      disable -nosetprimary mode.

              noclipboard     enable  -noclipboard mode.

              clipboard       disable -noclipboard mode.

              nosetclipboard  enable  -nosetclipboard mode.

              setclipboard    disable -nosetclipboard mode.

              seldir:str      set -seldir to "str"

              resend_cutbuffer resend the most recent CUTBUFFER0 copy

              resend_clipboard resend the most recent CLIPBOARD copy

              resend_primary   resend the most recent PRIMARY copy

              cursor:mode     enable  -cursor "mode".

              show_cursor     enable  showing a cursor.

              noshow_cursor   disable showing a cursor. (same as "nocursor")

              cursor_drag     enable  cursor changes during drag.

              nocursor_drag   disable cursor changes during drag.

              arrow:n         set -arrow to alternate n.

              xfixes          enable  xfixes cursor shape mode.

              noxfixes        disable xfixes cursor shape mode.

              alphacut:n      set -alphacut to n.

              alphafrac:f     set -alphafrac to f.

              alpharemove     enable  -alpharemove mode.

              noalpharemove   disable -alpharemove mode.

              alphablend      disable -noalphablend mode.

              noalphablend    enable  -noalphablend mode.

              cursorshape     disable -nocursorshape mode.

              nocursorshape   enable  -nocursorshape mode.

              cursorpos       disable -nocursorpos mode.

              nocursorpos     enable  -nocursorpos mode.

              xwarp           enable  -xwarppointer mode.

              noxwarp         disable -xwarppointer mode.

              always_inject   enable  -always_inject mode.

              noalways_inject disable -always_inject mode.

              buttonmap:str   set -buttonmap "str", empty to disable

              dragging        disable -nodragging mode.

              nodragging      enable  -nodragging mode.

              ncache          reenable -ncache mode.

              noncache        disable  -ncache mode.

              ncache_size:n   set -ncache size to n.

              ncache_cr       enable  -ncache_cr mode.

              noncache_cr     disable -ncache_cr mode.

              ncache_no_moveraise     enable  no_moveraise mode.

              noncache_no_moveraise   disable no_moveraise mode.

              ncache_no_dtchange      enable  ncache_no_dtchange mode.

              noncache_no_dtchange    disable ncache_no_dtchange mode.

              ncache_old_wm           enable  ncache_old_wm mode.

              noncache_old_wm         disable ncache_old_wm mode.

              ncache_no_rootpixmap    enable  ncache_no_rootpixmap.

              noncache_no_rootpixmap  disable ncache_no_rootpixmap.

              ncache_reset_rootpixmap recheck the root pixmap, ncrp

              ncache_keep_anims       enable  ncache_keep_anims.

              noncache_keep_anims     disable ncache_keep_anims.

              ncache_pad:n    set -ncache_pad to n.

              wireframe       enable  -wireframe mode. same as "wf"

              nowireframe     disable -wireframe mode. same as "nowf"

              wireframe:str   enable  -wireframe mode string.

              wireframe_mode:str enable  -wireframe mode string.

              wireframelocal  enable  wireframelocal. same as "wfl"

              nowireframe     disable wireframelocal. same as "nowfl"

              wirecopyrect:str set -wirecopyrect string. same as "wcr:"

              scrollcopyrect:str set -scrollcopyrect string. same "scr"

              noscrollcopyrect disable -scrollcopyrect__mode_. "noscr"

              scr_area:n      set -scr_area to n

              scr_skip:list   set -scr_skip to "list"

              scr_inc:list    set -scr_inc to "list"

              scr_keys:list   set -scr_keys to "list"

              scr_term:list   set -scr_term to "list"

              scr_keyrepeat:str set -scr_keyrepeat to "str"

              scr_parms:str   set -scr_parms parameters.

              fixscreen:str   set -fixscreen to "str".

              noxrecord       disable all use of RECORD extension.

              xrecord         enable  use of RECORD extension.

              reset_record    reset RECORD extension (if avail.)

              pointer_mode:n  set -pointer_mode to n. same as "pm"

              input_skip:n    set -input_skip to n.

              allinput        enable  use of -allinput mode.

              noallinput      disable use of -allinput mode.

              input_eagerly   enable  use of -input_eagerly mode.

              noinput_eagerly disable use of -input_eagerly mode.

              ssltimeout:n    set -ssltimeout to n.

              speeds:str      set -speeds to str.

              wmdt:str        set -wmdt to str.

              debug_pointer   enable  -debug_pointer, same as "dp"

              nodebug_pointer disable -debug_pointer, same as "nodp"

              debug_keyboard   enable  -debug_keyboard, same as "dk"

              nodebug_keyboard disable -debug_keyboard, same as "nodk"

              keycode:n       inject keystroke 'keycode' (xmodmap -pk)

              keycode:n,down  inject 'keycode' (down=0,1)

              keysym:str      inject keystroke 'keysym' (number/name)

              keysym:str,down inject 'keysym' (down=0,1)

              ptr:x,y,mask    inject pointer event x, y, button-mask

              fakebuttonevent:button,down direct XTestFakeButtonEvent.

              sleep:t         sleep floating point time t.

              get_xprop:p     get X property named 'p'.

              set_xprop:p:val set  X  property  named  'p'  to  'val'.   p  ->
              id=NNN:p for hex/dec window id.

              wininfo:id      get info about X window id.  use 'root' for root
              window, use +id for children.

              grab_state      get state of pointer and keyboard grab.

              pointer_pos     print XQueryPointer x,y cursor position.

              pointer_x       print XQueryPointer x cursor position.

              pointer_y       print XQueryPointer y cursor position.

              pointer_same    print XQueryPointer ptr on same screen.

              pointer_root    print XQueryPointer curr ptr rootwin.

              pointer_mask    print XQueryPointer button and mods mask

              mouse_x         print x11vnc's idea of cursor position.

              mouse_y         print x11vnc's idea of cursor position.

              noop            do nothing.

              defer:n         set -defer to n ms,same as deferupdate:n

              wait:n          set -wait to n ms.

              extra_fbur:n    set -extra_fbur to n.

              wait_ui:f       set -wait_ui factor to f.

              setdefer:n      set -setdefer to -2,-1,0,1, or 2.

              wait_bog        disable -nowait_bog mode.

              nowait_bog      enable  -nowait_bog mode.

              slow_fb:f       set -slow_fb to f seconds.

              xrefresh:f      set -xrefresh to f seconds.

              readtimeout:n   set read timeout to n seconds.

              nap             enable  -nap mode.

              nonap           disable -nap mode.

              sb:n            set -sb to n s, same as screen_blank:n

              fbpm            disable -nofbpm mode.

              nofbpm          enable  -nofbpm mode.

              dpms            disable -nodpms mode.

              nodpms          enable  -nodpms mode.

              forcedpms       enable  -forcedpms mode.

              noforcedpms     disable -forcedpms mode.

              clientdpms      enable  -clientdpms mode.

              noclientdpms    disable -clientdpms mode.

              noserverdpms    enable  -noserverdpms mode.

              serverdpms      disable -noserverdpms mode.

              noultraext      enable  -noultraext mode.

              ultraext        disable -noultraext mode.

              chatwindow      enable  local chatwindow mode.

              nochatwindow    disable local chatwindow mode.

              chaton          begin chat using local window.

              chatoff         end   chat using local window.

              xdamage         enable  xdamage polling hints.

              noxdamage       disable xdamage polling hints.

              xd_area:A       set -xd_area max pixel area to "A"

              xd_mem:f        set -xd_mem remembrance to "f"

              fs:frac         set -fs fraction to "frac", e.g. 0.5

              gaps:n          set -gaps to n.

              grow:n          set -grow to n.

              fuzz:n          set -fuzz to n.

              snapfb          enable  -snapfb mode.

              nosnapfb        disable -snapfb mode.

              rawfb:str       set -rawfb mode to "str".

              uinput_accel:f  set uinput_accel to f.

              uinput_thresh:n set uinput_thresh to n.

              uinput_reset:n  set uinput_reset to n ms.

              uinput_always:n set uinput_always to 1/0.

              progressive:n   set LibVNCServer -progressive slice  height  pa-
              rameter to n.

              desktop:str     set -desktop name to str for new clients.

              rfbport:n       set -rfbport to n.

              macnosaver      enable  -macnosaver mode.

              macsaver        disable -macnosaver mode.

              macnowait       enable  -macnowait  mode.

              macwait         disable -macnowait  mode.

              macwheel:n      set -macwheel to n.

              macnoswap       enable  -macnoswap mouse button mode.

              macswap         disable -macnoswap mouse button mode.

              macnoresize     enable  -macnoresize mode.

              macresize       disable -macnoresize mode.

              maciconanim:n   set -maciconanim to n.

              macmenu         enable  -macmenu  mode.

              macnomenu       disable -macmenu  mode.

              macuskbd        enable  -macuskbd mode.

              macnouskbd      disable -macuskbd mode.

              httpport:n      set -httpport to n.

              httpdir:dir     set -httpdir to dir (and enable http).

              enablehttpproxy   enable  -enablehttpproxy mode.

              noenablehttpproxy disable -enablehttpproxy mode.

              alwaysshared     enable  -alwaysshared mode.

              noalwaysshared    disable  -alwaysshared  mode.   (may interfere
              with other options)

              nevershared      enable  -nevershared mode.

              nonevershared    disable -nevershared mode.  (may interfere with
              other options)

              dontdisconnect   enable  -dontdisconnect mode.

              nodontdisconnect  disable  -dontdisconnect mode.  (may interfere
              with other options)

              debug_xevents   enable  debugging X events.

              nodebug_xevents disable debugging X events.

              debug_xdamage   enable  debugging X DAMAGE mechanism.

              nodebug_xdamage disable debugging X DAMAGE mechanism.

              debug_wireframe enable   debugging wireframe mechanism.

              nodebug_wireframe disable debugging wireframe mechanism.

              debug_scroll    enable  debugging scrollcopy mechanism.

              nodebug_scroll  disable debugging scrollcopy mechanism.

              debug_tiles     enable  -debug_tiles

              nodebug_tiles   disable -debug_tiles

              debug_grabs     enable  -debug_grabs

              nodebug_grabs   disable -debug_grabs

              debug_sel       enable  -debug_sel

              nodebug_sel     disable -debug_sel

              debug_ncache    enable  -debug_ncache

              nodebug_ncache  disable -debug_ncache

              dbg             enable  -dbg crash shell

              nodbg           disable -dbg crash shell

              noremote        disable the -remote command processing, it  can-
              not be turned back on.

              bcx_xattach:str  This remote control command is for use with the
              BARCO xattach program or the x2x program.  Both  of  these  pro-
              grams  are for 'pointer and keyboard' sharing between separate X
              displays.  In general the two displays are usually nearby,  e.g.
              on  the  same  desk,  and this allows the user to share a single
              pointer and keyboard between them.  The user moves the mouse  to
              an  edge  and  then  the  mouse pointer appears to 'jump' to the
              other display screen.  Thus it emulates what a single  X  server
              would  do for two screens (e.g. :0.0 and :0.1) The illusion of a
              single Xserver with multiple screens is achieved  by  forwarding
              events to the 2nd one via the XTEST extension.

              What  the  x11vnc  bcx_xattach  command  does is to perform some
              pointer movements to try to INDUCE xattach/x2x to 'jump' to  the
              other  display.   In what follows the 'master' display refers to
              the one that when it has 'focus' it is basically  doing  nothing
              besides  watching for the mouse to go over an edge.  The 'slave'
              display refers to the one to which the  mouse  and  keyboard  is
              redirected to once an edge in the master has been crossed.  Note
              that the x11vnc executing the bcx_xattach command  MUST  be  the
              one connected to the *master* display.

              Also  note  that when input is being redirected (via XTEST) from
              the master display to the slave display,  the  master  display's
              pointer  and  keyboard are *grabbed* by xattach/x2x.  x11vnc can
              use this info to verify that the master/slave  mode  change  has
              taken  place  correctly.   If  you specify the "ifneeded" option
              (see below) and the initial grab state is that  of  the  desired
              final   state,  then  no  pointer  movements  are  injected  and
              "DONE,GRAB_OK" is returned.

              "str" must contain one of "up", "down", "left",  or  "right"  to
              indicate  the  direction of the 'jump'.  "str" must also contain
              one of "master_to_slave" or "slave_to_master"  to  indicate  the
              type of mode change induced by the jump.  Use "M2S" and "S2M" as
              shorter aliases.

              "str" may be a "+" separated list of additional tuning  options.
              The  "shift=n"  option  indicates  an offset shift position away
              from (0,0) (default 20).  "final=x+y" specifies the final  posi-
              tion  of  the cursor at the end of the normal move sequence; de-
              fault 30+30.  "extra_move=x+y" means to do one more pointer move
              after  "final"  to x+y.  "dt=n" sets the sleep time in millisec-
              onds between pointer moves (default: 40ms)  "retry=n"  specifies
              the  maximum  number  of retries if the grab state change fails.
              "ifneeded" means to not apply the pointer movements if the  ini-
              tial  grab  state  is  that  of  the  desired  final state. "no-
              grabcheck" means to not check if the grab state changed  as  ex-
              pected and only apply the pointer movements (default is to check
              the grab states.)

              If you do not specify "up", etc., to bcx_xattach nothing will be
              attempted  and  the  command  returns  the string FAIL,NO_DIREC-
              TION_SPECIFIED.  If you  do  not  specify  "master_to_slave"  or
              "M2S",  etc.,  to  bcx_xattach nothing will be attempted and the
              command returns the string FAIL,NO_MODE_CHANGE_SPECIFIED.

              Otherwise, the returned string will contain "DONE".  It will  be
              "DONE,GRAB_OK"  if  the  grab  state  changed as expected (or if
              "ifneeded" was supplied and the initial grab state  was  already
              the  desired one.)  If the initial grab state was incorrect, but
              the   final   grab   state    was    correct    then    it    is
              "DONE,GRAB_FAIL_INIT".   If  the initial grab state was correct,
              but  the  final  grab   state   was   incorrect   then   it   is
              "DONE,GRAB_FAIL_FINAL".   If  both  are  incorrect  it  will  be
              "DONE,GRAB_FAIL".  Under grab failure the string  will  be  fol-
              lowed  by  ":p1,k1-p2,k2"  where   p1,k1  indicates  the initial
              pointer and keyboard grab states and p2,k2 the  final  ones.  If
              GRAB_FAIL  or GRAB_FAIL_FINAL occurs, the action will be retried
              up to 3 times; trying to reset the state and sleeping a bit  be-
              tween  each  try.   Set retry=n to adjust the number of retries,
              zero to disable retries.

              Examples:  -R  bcx_xattach:down+M2S  -R  bcx_xattach:up+S2M   -R
              bcx_xattach:up+S2M+nograbcheck+dt=30 -R bcx_xattach:down+M2S+ex-
              tra_move=100+100

              or use -Q instead of -R to retrieve the result text.

              End of the bcx_xattach:str description.

              The vncconnect(1) command from standard  VNC  distributions  may
              also  be used if string is prefixed with "cmd=" E.g. 'vncconnect
              cmd=stop'.  Under some circumstances xprop(1)  can  used  if  it
              supports -set (see the FAQ).

              If  "-connect  /path/to/file"  has  been supplied to the running
              x11vnc server then that file can  be  used  as  a  communication
              channel  (this  is  the  only  way to remote control one of many
              x11vnc's polling the same X display) Simply run:  'x11vnc  -con-
              nect  /path/to/file  -remote  ...'  or you can directly write to
              the file via something like: "echo  cmd=stop  >  /path/to/file",
              etc.

       -query variable

              Like  -remote, except just query the value of variable.  "-Q" is
              an alias for "-query".  Multiple queries can be done by separat-
              ing variables by commas, e.g. -query var1,var2. The results come
              back in the  form  ans=var1:value1,ans=var2:value2,...   to  the
              standard output.  If a variable is read-only, it comes back with
              prefix "aro=" instead of "ans=".

              Some -remote commands are pure actions that do not make sense as
              variables, e.g. "stop" or "disconnect", in these cases the value
              returned is "N/A".  To direct a query straight to the X11VNC_RE-
              MOTE property or connect file use "qry=..." instead of "cmd=..."

              ans=  stop quit exit shutdown ping resend_cutbuffer resend_clip-
              board resend_primary blacken zero refresh reset close disconnect
              id_cmd id sid waitmapped nowaitmapped clip flashcmap noflashcmap
              shiftcmap truecolor notruecolor overlay nooverlay overlay_cursor
              overlay_yescursor  nooverlay_nocursor  nooverlay_cursor  noover-
              lay_yescursor overlay_nocursor 8to24 no8to24  8to24_opts  24to32
              no24to32  visual  scale  scale_cursor viewonly noviewonly shared
              noshared forever noforever once timeout  tightfilexfer  notight-
              filexfer  ultrafilexfer  noultrafilexfer  rfbversion  deny  lock
              nodeny unlock avahi mdns zeroconf noavahi nomdns nozeroconf con-
              nect  proxy allowonce allow noipv6 ipv6 noipv4 ipv4 no6 6 local-
              host nolocalhost listen lookup nolookup accept afteraccept  gone
              shm   noshm   flipbyteorder  noflipbyteorder  onetile  noonetile
              solid_color solid nosolid  blackout  xinerama  noxinerama  xtrap
              noxtrap  xrandr  noxrandr xrandr_mode rotate padgeom quiet q no-
              quiet  modtweak  nomodtweak  xkb   noxkb   capslock   nocapslock
              skip_lockkeys    noskip_lockkeys    skip_keycodes    sloppy_keys
              nosloppy_keys skip_dups  noskip_dups  add_keysyms  noadd_keysyms
              clear_mods   noclear_mods   clear_keys   noclear_keys  clear_all
              clear_locks keystate remap repeat norepeat fb nofb  bell  nobell
              sendbell  sel  nosel  primary  noprimary setprimary nosetprimary
              clipboard noclipboard setclipboard nosetclipboard seldir cursor-
              shape  nocursorshape  cursorpos  nocursorpos  cursor_drag nocur-
              sor_drag cursor show_cursor noshow_cursor nocursor arrow  xfixes
              noxfixes xdamage noxdamage xd_area xd_mem alphacut alphafrac al-
              pharemove  noalpharemove  alphablend  noalphablend  xwarppointer
              xwarp  noxwarppointer noxwarp always_inject noalways_inject but-
              tonmap     dragging     nodragging     ncache_cr     noncache_cr
              ncache_no_moveraise   noncache_no_moveraise   ncache_no_dtchange
              noncache_no_dtchange ncache_no_rootpixmap noncache_no_rootpixmap
              ncache_reset_rootpixmap ncrp ncache_keep_anims noncache_keep_an-
              ims ncache_old_wm  noncache_old_wm  ncache_pad  ncache  noncache
              ncache_size debug_ncache nodebug_ncache wireframe_mode wireframe
              wf nowireframe nowf wireframelocal  wfl  nowireframelocal  nowfl
              wirecopyrect  wcr nowirecopyrect nowcr scr_area scr_skip scr_inc
              scr_keys scr_term scr_keyrepeat scr_parms scrollcopyrect scr no-
              scrollcopyrect  noscr  fixscreen  noxrecord xrecord reset_record
              pointer_mode pm  input_skip  allinput  noallinput  input_eagerly
              noinput_eagerly  input  grabkbd nograbkbd grabptr nograbptr gra-
              balways nograbalways grablocal  client_input  ssltimeout  speeds
              wmdt  debug_pointer  dp  nodebug_pointer  nodp debug_keyboard dk
              nodebug_keyboard nodk keycode keysym ptr  fakebuttonevent  sleep
              get_xprop set_xprop wininfo bcx_xattach deferupdate defer setde-
              fer extra_fbur wait_ui wait_bog nowait_bog slow_fb xrefresh wait
              readtimeout  nap  nonap  sb screen_blank fbpm nofbpm dpms nodpms
              clientdpms  noclientdpms  forcedpms   noforcedpms   noserverdpms
              serverdpms  noultraext  ultraext  chatwindow nochatwindow chaton
              chatoff fs gaps grow fuzz  snapfb  nosnapfb  rawfb  uinput_accel
              uinput_thresh  uinput_reset  uinput_always  progressive  rfbport
              http nohttp httpport httpdir  enablehttpproxy  noenablehttpproxy
              alwaysshared  noalwaysshared nevershared noalwaysshared dontdis-
              connect nodontdisconnect desktop  debug_xevents  nodebug_xevents
              debug_xevents  debug_xdamage  nodebug_xdamage  debug_xdamage de-
              bug_wireframe  nodebug_wireframe  debug_wireframe   debug_scroll
              nodebug_scroll  debug_scroll debug_tiles dbt nodebug_tiles nodbt
              debug_tiles debug_grabs nodebug_grabs debug_sel nodebug_sel  dbg
              nodbg  macnosaver macsaver nomacnosaver macnowait macwait nomac-
              nowait macwheel macnoswap macswap nomacnoswap macnoresize macre-
              size  nomacnoresize  maciconanim macmenu macnomenu nomacmenu ma-
              cuskbd nomacuskbd noremote

              aro=  noop display vncdisplay  icon_mode  autoport  loop  loopbg
              desktopname  guess_desktop  guess_dbus http_url auth xauth users
              rootshift  clipshift  scale_str  scaled_x  scaled_y  scale_numer
              scale_denom  scale_fac_x  scale_fac_y  scaling_blend scaling_no-
              mult4 scaling_pad scaling_interpolate  inetd  privremote  unsafe
              safer   nocmds  passwdfile  unixpw  unixpw_nis  unixpw_list  ssl
              ssl_pem sslverify stunnel stunnel_pem https httpsredir usepw us-
              ing_shm  logfile  o flag rmflag rc norc h help V version lastmod
              bg sigpipe threads readrate netrate netlatency pipeinput clients
              client_count   pid   ext_xtest   ext_xtrap  ext_xrecord  ext_xkb
              ext_xshm   ext_xinerama   ext_overlay   ext_xfixes   ext_xdamage
              ext_xrandr   rootwin  num_buttons  button_mask  mouse_x  mouse_y
              grab_state   pointer_pos   pointer_x   pointer_y    pointer_same
              pointer_root  pointer_mask  bpp  depth indexed_color dpy_x dpy_y
              wdpy_x wdpy_y off_x off_y cdpy_x cdpy_y  coff_x  coff_y  rfbauth
              passwd viewpasswd

       -QD variable

              Just  like  -query  variable,  but returns the default value for
              that parameter (no running x11vnc server is consulted)

       -sync

              By default -remote commands are run asynchronously, that is, the
              request  is posted and the program immediately exits.  Use -sync
              to have the program wait for an acknowledgement from the  x11vnc
              server  that command was processed (somehow).  On the other hand
              -query requests are always processed synchronously because  they
              have to wait for the answer.

              Also  note that if both -remote and -query requests are supplied
              on the command  line,  the  -remote  is  processed  first  (syn-
              chronously:  no  need for -sync), and then the -query request is
              processed in the normal way.  This allows for a reliable way  to
              see if the -remote command was processed by querying for any new
              settings.  Note however that there is timeout of a  few  seconds
              (see the next paragraph) so if the x11vnc takes longer than that
              to process the requests the requester will think that a  failure
              has taken place.

              The  default  is  to  wait 3.5 seconds.  Or if cmd=stop only 1.0
              seconds.  If cmd matches 'script:' then it will wait up to  10.0
              seconds.   Set  X11VNC_SYNC_TIMEOUT to the number of seconds you
              want it to wait.

       -query_retries str

              If a query fails to get a response from an x11vnc server,  retry
              up  to  n  times.  str is specified as n[:t][/match]  Optionally
              the delay between tries may be specified by "t" a floating point
              time  (default  0.5 seconds.)  Note: the response is not checked
              for validity or whether it corresponds to the query  sent.   The
              query  "ping:mystring" may be used to help uniquely identify the
              query.  Optionally, a matching string after a "/" will  be  used
              to check the result text.  Up to n retries will take place until
              the matching string is found in the output text.  If  the  match
              string is never found the program's exit code is 1; if the match
              is found it exits with 0.  Note that there may be stdout printed
              for each retry (i.e. multiple lines printed out to stdout.)  Ex-
              ample: -query_retries 4:1.5/grab_state

       -remote_prefix str

              Enable a remote-control communication channel for connected  VNC
              clients.   str is a non-empty string. If a VNC client sends rfb-
              CutText having the prefix str then the part  after  it  is  pro-
              cessed  as  though it were sent via 'x11vnc -remote ...'.  If it
              begins with neither 'cmd=' nor 'qry=' then  'qry='  is  assumed.
              Any corresponding output text for that remote control command is
              sent back to all client as rfbCutText.  The returned  output  is
              also prefixed with str.  Example: -remote_prefix DO_THIS:

              Note  that enabling -remote_prefix allows the remote VNC viewers
              to run x11vnc -remote commands.  Do not use this option if  they
              are not to be trusted.

       -noremote, -yesremote

              Do  not  process  any  remote  control  commands or queries.  Do
              process remote control commands or queries.  Default: -yesremote

              A note about security wrt remote control commands.   If  someone
              can  connect to the X display and change the property X11VNC_RE-
              MOTE, then they can remotely control x11vnc.  Normally access to
              the  X  display  is  protected.   Note  that  if they can modify
              X11VNC_REMOTE on the X server, they have enough  permissions  to
              also  run their own x11vnc and thus have complete control of the
              desktop.  If the   "-connect  /path/to/file"  channel  is  being
              used,  obviously  anyone  who can write to /path/to/file can re-
              motely control x11vnc.  So be sure to protect the X display  and
              that file's write permissions.  See -privremote below.

              If  you  are  paranoid  and do not think -noremote is enough, to
              disable  the  X11VNC_REMOTE  property  channel  completely   use
              -novncconnect,  or  use the -safer option that shuts many things
              off.

       -unsafe

              A few  remote  commands  are  disabled  by  default  (currently:
              id:pick,  accept:<cmd>,  gone:<cmd>,  and rawfb:setup:<cmd>) be-
              cause they are associated with running  external  programs.   If
              you  specify -unsafe, then these remote-control commands are al-
              lowed.  Note that you can still specify these parameters on  the
              command line, they just cannot be invoked via remote-control.

       -safer

              Equivalent  to: -novncconnect -noremote and prohibiting -gui and
              the -connect file. Shuts off communication channels.

       -privremote

              Perform some sanity checks and disable  remote-control  commands
              if  it  appears that the X DISPLAY and/or connectfile can be ac-
              cessed by other users.  Once remote-control is disabled it  can-
              not be turned back on.

       -nocmds

              No  external  commands  (e.g.   system(3) , popen(3) , exec(3) )
              will be run at all.

       -allowedcmds list

              list contains a comma separated list of the only  external  com-
              mands that can be run.  The full list of associated options is:

              stunnel,  ssl,  unixpw, WAIT, zeroconf, id, accept, afteraccept,
              gone,  pipeinput,   v4l-info,   rawfb-setup,   dt,   gui,   ssh,
              storepasswd, passwdfile, custom_passwd, findauth, crash.

              See each option's help to learn the associated external command.
              Note that the -nocmds option takes precedence and  disables  all
              external commands.

       -deny_all

              For  use  with  -remote  nodeny:  start out denying all incoming
              clients until "-remote nodeny" is used to let them in.

       These options are passed to LibVNCServer:

       -rfbport port

              TCP port for RFB protocol

       -rfbwait time

              max time in ms to wait for RFB client

       -rfbauth passwd-file

              use authentication on RFB  protocol  (use  'x11vnc  -storepasswd
              pass file' to create a password file)

       -rfbversion 3.x

              Set the version of the RFB we choose to advertise

       -permitfiletransfer

              permit file transfer support

       -passwd plain-password

              use  authentication (use plain-password as password, USE AT YOUR
              RISK)

       -deferupdate time

              time in ms to defer updates (default 40)

       -deferptrupdate time

              time in ms to defer pointer updates (default none)

       -desktop name

              VNC desktop name (default "LibVNCServer")

       -alwaysshared

              always treat new clients as shared

       -nevershared

              never treat new clients as shared

       -dontdisconnect

              don't disconnect existing clients when a new non-shared  connec-
              tion comes in (refuse new connection instead)

       -httpdir dir-path

              enable http server using dir-path home

       -httpport portnum

              use portnum for http connection

       -enablehttpproxy

              enable http proxy support

       -progressive height

              enable progressive updating for slow links

       -listen ipaddr

              listen  for  connections  only  on  network  interface with addr
              ipaddr. '-listen localhost' and hostname work too.

       libvncserver-tight-extension options:

       -disablefiletransfer

              disable file transfer

       -ftproot string

              set ftp root

FILES
       $HOME/.x11vncrc, $HOME/.Xauthority

ENVIRONMENT
       DISPLAY, XAUTHORITY, HOME

       The following are set for the auxiliary commands run by -accept,  -gone
       and other cases:

       RFB_CLIENT_IP,    RFB_CLIENT_PORT,    RFB_SERVER_IP,   RFB_SERVER_PORT,
       RFB_X11VNC_PID,  RFB_CLIENT_ID,  RFB_CLIENT_COUNT,  RFB_MODE  RFB_STATE
       RFB_LOGIN_VIEWONLY    RFB_LOGIN_TIME    RFB_CURRENT_TIME   RFB_USERNAME
       RFB_SSL_CLIENT_CERT

SEE ALSO
       vncviewer(1),  vncpasswd(1),  vncconnect(1),   vncserver(1),   Xvnc(1),
       xev(1),  xdpyinfo(1),  xwininfo(1),  xprop(1),  xmodmap(1),  xrandr(1),
       Xserver(1),  xauth(1),  xhost(1),  Xsecurity(7),  xmessage(1),  XGetIm-
       age(3X11),  ipcrm(1),  inetd(1),  xdm(1), gdm(1), kdm(1), ssh(1), stun-
       nel(8),   su(1),    http://www.tightvnc.com,    http://www.realvnc.com,
       http://www.karlrunge.com/x11vnc/, http://www.karlrunge.com/x11vnc/#faq,
       https://github.com/LibVNC/x11vnc

AUTHORS
       x11vnc was written by Karl J. Runge <runge@karlrunge.com>, it  is  part
       of  the  LibVNCServer project <https://github.com/LibVNC/libvncserver>.
       This manual page is  based  one  the  one  written  by  Ludovic  Drolez
       <ldrolez@debian.org>,  for the Debian project (both may be used by oth-
       ers).

x11vnc                           February 2018                       X11VNC(1)

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