CURLMOPT_SOCKETFUNCTION(3) curl_multi_setopt optionsCURLMOPT_SOCKETFUNCTION(3)
NAME
CURLMOPT_SOCKETFUNCTION - callback informed about what to wait for
SYNOPSIS
#include <curl/curl.h>
int socket_callback(CURL *easy, /* easy handle */
curl_socket_t s, /* socket */
int what, /* describes the socket */
void *userp, /* private callback pointer */
void *socketp); /* private socket pointer */
CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_SOCKETFUNCTION, socket_callback);
DESCRIPTION
Pass a pointer to your callback function, which should match the proto-
type shown above.
When the curl_multi_socket_action(3) function is called, it informs the
application about updates in the socket (file descriptor) status by do-
ing none, one, or multiple calls to the socket_callback. The callback
function gets status updates with changes since the previous time the
callback was called. If the given callback pointer is set to NULL, no
callback will be called.
CALLBACK ARGUMENTS
easy identifies the specific transfer for which this update is related.
s is the specific socket this function invocation concerns. If the what
argument is not CURL_POLL_REMOVE then it holds information about what
activity on this socket the application is supposed to monitor. Subse-
quent calls to this callback might update the what bits for a socket
that is already monitored.
The socket callback should return 0 on success, and -1 on error. If
this callback returns error, all transfers currently in progress in
this multi handle will be aborted and fail.
userp is set with CURLMOPT_SOCKETDATA(3).
socketp is set with curl_multi_assign(3) or will be NULL.
The what parameter informs the callback on the status of the given
socket. It can hold one of these values:
CURL_POLL_IN
Wait for incoming data. For the socket to become readable.
CURL_POLL_OUT
Wait for outgoing data. For the socket to become writable.
CURL_POLL_INOUT
Wait for incoming and outgoing data. For the socket to become
readable or writable.
CURL_POLL_REMOVE
The specified socket/file descriptor is no longer used by
libcurl.
DEFAULT
NULL (no callback)
PROTOCOLS
All
EXAMPLE
static int sock_cb(CURL *e, curl_socket_t s, int what, void *cbp, void *sockp)
{
GlobalInfo *g = (GlobalInfo*) cbp;
SockInfo *fdp = (SockInfo*) sockp;
if(what == CURL_POLL_REMOVE) {
remsock(fdp);
}
else {
if(!fdp) {
addsock(s, e, what, g);
}
else {
setsock(fdp, s, e, what, g);
}
}
return 0;
}
main()
{
GlobalInfo setup;
/* ... use socket callback and custom pointer */
curl_multi_setopt(multi, CURLMOPT_SOCKETFUNCTION, sock_cb);
curl_multi_setopt(multi, CURLMOPT_SOCKETDATA, &setup);
}
AVAILABILITY
Added in 7.15.4
RETURN VALUE
Returns CURLM_OK.
SEE ALSO
CURLMOPT_SOCKETDATA(3), curl_multi_socket_action(3), CURLMOPT_TIMER-
FUNCTION(3)
libcurl 7.81.0 December 02, 2021 CURLMOPT_SOCKETFUNCTION(3)
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