CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS(3)                  curl_easy_setopt options

NAME
       CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS - head start for ipv6 for happy
       eyeballs

SYNOPSIS
       #include <curl/curl.h>

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

DESCRIPTION
       Happy eyeballs is an algorithm that attempts to connect to both IPv4
       and IPv6 addresses for dual-stack hosts, preferring IPv6 first for
       timeout milliseconds. If the IPv6 address cannot be connected to within
       that time then a connection attempt is made to the IPv4 address in
       parallel. The first connection to be established is the one that is
       used.

       The range of suggested useful values for timeout is limited. Happy
       Eyeballs RFC 6555 says "It is RECOMMENDED that connection attempts be
       paced 150-250 ms apart to balance human factors against network load."
       libcurl currently defaults to 200 ms. Firefox and Chrome currently
       default to 300 ms.

DEFAULT
       CURL_HET_DEFAULT (currently defined as 200L)

EXAMPLE
       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
         curl_easy_setopt(curl, CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS, 300L);

         curl_easy_perform(curl);

         /* always cleanup */
         curl_easy_cleanup(curl);
       }

AVAILABILITY
       Added in 7.59.0

RETURN VALUE
       Returns CURLE_OK

libcurl 7.77.0                 November 4, 2020
                                          CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS(3)