CURLOPT_CONNECT_ONLY(3) Library Functions Manual CURLOPT_CONNECT_ONLY(3)
NAME
CURLOPT_CONNECT_ONLY - stop when connected to target server
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CONNECT_ONLY, long only);
DESCRIPTION
Pass a long. If the parameter equals 1, it tells the library to perform
all the required proxy authentication and connection setup, but no data
transfer, and then return.
The option can be used to simply test a connection to a server, but is
more useful when used with the CURLINFO_ACTIVESOCKET(3) option to
curl_easy_getinfo(3) as the library can set up the connection and then
the application can obtain the most recently used socket for special
data transfers.
Since 7.86.0, this option can be set to '2' and if HTTP or WebSocket are
used, libcurl performs the request and reads all response headers before
handing over control to the application.
Transfers marked connect only do not reuse any existing connections and
connections marked connect only are not allowed to get reused.
If the connect only transfer is done using the multi interface, the par-
ticular easy handle must remain added to the multi handle for as long as
the application wants to use it. Once it has been removed with
curl_multi_remove_handle(3), curl_easy_send(3) and curl_easy_recv(3) do
not function.
DEFAULT
0
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode ret;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
ret = curl_easy_perform(curl);
if(ret == CURLE_OK) {
/* only connected */
}
}
}
HISTORY
WS and WSS support added in 7.86.0.
AVAILABILITY
Added in curl 7.15.2
RETURN VALUE
curl_easy_setopt(3) returns a CURLcode indicating success or error.
CURLE_OK (0) means everything was OK, non-zero means an error occurred,
see libcurl-errors(3).
SEE ALSO
CURLOPT_HTTPPROXYTUNNEL(3), CURLOPT_VERBOSE(3), curl_easy_recv(3),
curl_easy_send(3)
libcurl 2026-07-12 CURLOPT_CONNECT_ONLY(3)
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