CURLOPT_CONNECT_TO(3) curl_easy_setopt options CURLOPT_CONNECT_TO(3)
NAME
CURLOPT_CONNECT_TO - connect to a specific host and port instead of the
URL's host and port
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CONNECT_TO,
struct curl_slist *connect_to);
DESCRIPTION
Pass a pointer to a linked list of strings with "connect to" informa-
tion to use for establishing network connections with this handle. The
linked list should be a fully valid list of struct curl_slist structs
properly filled in. Use curl_slist_append(3) to create the list and
curl_slist_free_all(3) to clean up an entire list.
Each single string should be written using the format HOST:PORT:CON-
NECT-TO-HOST:CONNECT-TO-PORT where HOST is the host of the request,
PORT is the port of the request, CONNECT-TO-HOST is the host name to
connect to, and CONNECT-TO-PORT is the port to connect to.
The first string that matches the request's host and port is used.
Dotted numerical IP addresses are supported for HOST and CONNECT-TO-
HOST. A numerical IPv6 address must be written within [brackets].
Any of the four values may be empty. When the HOST or PORT is empty,
the host or port will always match (the request's host or port is ig-
nored). When CONNECT-TO-HOST or CONNECT-TO-PORT is empty, the "connect
to" feature will be disabled for the host or port, and the request's
host or port will be used to establish the network connection.
This option is suitable to direct the request at a specific server,
e.g. at a specific cluster node in a cluster of servers.
The "connect to" host and port are only used to establish the network
connection. They do NOT affect the host and port that are used for
TLS/SSL (e.g. SNI, certificate verification) or for the application
protocols.
In contrast to CURLOPT_RESOLVE(3), the option CURLOPT_CONNECT_TO(3)
does not pre-populate the DNS cache and therefore it does not affect
future transfers of other easy handles that have been added to the same
multi handle.
The "connect to" host and port are ignored if they are equal to the
host and the port in the request URL, because connecting to the host
and the port in the request URL is the default behavior.
If an HTTP proxy is used for a request having a special "connect to"
host or port, and the "connect to" host or port differs from the re-
quest's host and port, the HTTP proxy is automatically switched to tun-
nel mode for this specific request. This is necessary because it is not
possible to connect to a specific host or port in normal (non-tunnel)
mode.
When this option is passed to curl_easy_setopt(3), libcurl will not
copy the entire list so you must keep it around until you no longer use
this handle for a transfer before you call curl_slist_free_all(3) on
the list.
DEFAULT
NULL
PROTOCOLS
All
EXAMPLE
CURL *curl;
struct curl_slist *connect_to = NULL;
connect_to = curl_slist_append(NULL, "example.com::server1.example.com:");
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_CONNECT_TO, connect_to);
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
curl_easy_perform(curl);
/* always cleanup */
curl_easy_cleanup(curl);
}
curl_slist_free_all(connect_to);
AVAILABILITY
Added in 7.49.0
RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
if not.
SEE ALSO
CURLOPT_URL(3), CURLOPT_RESOLVE(3), CURLOPT_FOLLOWLOCATION(3), CUR-
LOPT_HTTPPROXYTUNNEL(3),
libcurl 7.81.0 September 08, 2021 CURLOPT_CONNECT_TO(3)
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