CURLOPT_CONNECTTIMEOUT_MS - Man Page

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CONNECTTIMEOUT_MS,
                          long timeout);

Pass a long. It sets the maximum time in milliseconds that you allow the connection phase to take. This timeout only limits the connection phase, it has no impact once libcurl has connected. The connection phase includes the name resolve (DNS) and all protocol handshakes and negotiations until there is an established connection with the remote side.

Set this option to zero to switch to the default built-in connection timeout - 300 seconds. See also the CURLOPT_TIMEOUT_MS(3) option.

CURLOPT_CONNECTTIMEOUT(3) is the same function but set in seconds.

If both CURLOPT_CONNECTTIMEOUT(3) and CURLOPT_CONNECTTIMEOUT_MS(3) are set, the value set last is used.

The connection timeout is included in the general all-covering CURLOPT_TIMEOUT_MS(3):

With CURLOPT_CONNECTTIMEOUT_MS(3) set to 3000 and CURLOPT_TIMEOUT_MS(3) set to 5000, the operation can never last longer than 5000 milliseconds, and the connection phase cannot last longer than 3000 milliseconds.

With CURLOPT_CONNECTTIMEOUT_MS(3) set to 4000 and CURLOPT_TIMEOUT_MS(3) set to 2000, the operation can never last longer than 2000 milliseconds. Including the connection phase.

This option may cause libcurl to use the SIGALRM signal to timeout system calls on builds not using asynch DNS. In Unix-like systems, this might cause signals to be used unless CURLOPT_NOSIGNAL(3) is set.

300000

This functionality affects all supported protocols

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

    /* complete connection within 10000 milliseconds */
    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT_MS, 10000L);

    curl_easy_perform(curl);
  }
}

Added in curl 7.16.2

Returns CURLE_OK

CURLOPT_LOW_SPEED_LIMIT(3), CURLOPT_MAX_RECV_SPEED_LARGE(3), CURLOPT_TIMEOUT_MS(3)

curl_easy_setopt(3), CURLMOPT_MAX_HOST_CONNECTIONS(3), CURLMOPT_MAX_TOTAL_CONNECTIONS(3), CURLOPT_ACCEPTTIMEOUT_MS(3), CURLOPT_CONNECTTIMEOUT(3), CURLOPT_DNS_CACHE_TIMEOUT(3), CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS(3), libcurl-symbols(3).