CURLOPT_HAPPY_EYEBALLS_TIMEcurlMeasy_setopCURLOPTnHAPPY_EYEBALLS_TIMEOUT_MS(3)
NAME
CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS - head start for ipv6 for happy eye-
balls
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 par-
allel. The first connection to be established is the one that is used.
The range of suggested useful values for timeout is limited. Happy Eye-
balls 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 de-
fault to 300 ms.
DEFAULT
CURL_HET_DEFAULT (currently defined as 200L)
PROTOCOLS
All except FILE
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
SEE ALSO
CURLOPT_CONNECTTIMEOUT_MS(3), CURLOPT_TIMEOUT(3), CUR-
LOPT_LOW_SPEED_LIMIT(3),
libcurl 7.81.0 November 26CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS(3)
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