1CURLOPT_HAPPY_EYEBALLS_TIMEOcUuTr_lM_Se(a3s)y_setoptCUoRpLtOiPoTn_sHAPPY_EYEBALLS_TIMEOUT_MS(3)
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NAME

6       CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS  - head start for ipv6 for happy eye‐
7       balls
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SYNOPSIS

10       #include <curl/curl.h>
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12       CURLcode  curl_easy_setopt(CURL  *handle,  CURLOPT_HAPPY_EYEBALLS_TIME‐
13       OUT_MS, long timeout);
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DESCRIPTION

16       Happy  eyeballs  is  an algorithm that attempts to connect to both IPv4
17       and IPv6 addresses for dual-stack  hosts,  preferring  IPv6  first  for
18       timeout milliseconds. If the IPv6 address cannot be connected to within
19       that time then a connection attempt is made to the IPv4 address in par‐
20       allel. The first connection to be established is the one that is used.
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22       The range of suggested useful values for timeout is limited. Happy Eye‐
23       balls RFC 6555 says "It is  RECOMMENDED  that  connection  attempts  be
24       paced  150-250 ms apart to balance human factors against network load."
25       libcurl currently defaults to 200 ms. Firefox and Chrome currently  de‐
26       fault to 300 ms.
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DEFAULT

29       CURL_HET_DEFAULT (currently defined as 200L)
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EXAMPLE

32       CURL *curl = curl_easy_init();
33       if(curl) {
34         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
35         curl_easy_setopt(curl, CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS, 300L);
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37         curl_easy_perform(curl);
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39         /* always cleanup */
40         curl_easy_cleanup(curl);
41       }
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AVAILABILITY

44       Added in 7.59.0
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RETURN VALUE

47       Returns CURLE_OK
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51libcurl 7.76.1                 November 04,CU2R0L2O0PT_HAPPY_EYEBALLS_TIMEOUT_MS(3)
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