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| .TH CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS 3 "1 Feb 2018" "libcurl 7.59.0" "curl_easy_setopt options" |
| .SH NAME |
| CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS \- head start for ipv6 for happy eyeballs |
| .SH SYNOPSIS |
| #include <curl/curl.h> |
| |
| CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS, long timeout); |
| .SH DESCRIPTION |
| Happy eyeballs is an algorithm that attempts to connect to both IPv4 and IPv6 |
| addresses for dual-stack hosts, preferring IPv6 first for \fItimeout\fP |
| 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 \fItimeout\fP 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. |
| .SH DEFAULT |
| CURL_HET_DEFAULT (currently defined as 200L) |
| .SH EXAMPLE |
| .nf |
| 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); |
| } |
| .fi |
| .SH AVAILABILITY |
| Added in 7.59.0 |
| .SH RETURN VALUE |
| Returns CURLE_OK |
