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.\" **************************************************************************
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.\" * _ _ ____ _
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.\" * Project ___| | | | _ \| |
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.\" * / __| | | | |_) | |
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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2021-09-01 16:26:36 +08:00
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.\" * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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2020-11-04 21:02:01 +08:00
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.\" * are also available at https://curl.se/docs/copyright.html.
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.\" *
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.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" * furnished to do so, under the terms of the COPYING file.
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.\" *
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.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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.\" * KIND, either express or implied.
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.\" *
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.\" * SPDX-License-Identifier: curl
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2022-05-17 17:16:50 +08:00
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.\" *
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.\" **************************************************************************
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.\"
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2018-02-22 04:16:50 +08:00
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.TH CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS 3 "1 Feb 2018" "libcurl 7.59.0" "curl_easy_setopt options"
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2018-01-31 08:33:51 +08:00
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.SH NAME
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2022-09-21 05:30:19 +08:00
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CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS \- head start for IPv6 for happy eyeballs
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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2021-11-26 21:20:18 +08:00
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS,
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long timeout);
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.fi
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2018-01-31 08:33:51 +08:00
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.SH DESCRIPTION
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Happy eyeballs is an algorithm that attempts to connect to both IPv4 and IPv6
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addresses for dual-stack hosts, preferring IPv6 first for \fItimeout\fP
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milliseconds. If the IPv6 address cannot be connected to within that time then
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a connection attempt is made to the IPv4 address in parallel. The first
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connection to be established is the one that is used.
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The range of suggested useful values for \fItimeout\fP is limited. Happy
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Eyeballs RFC 6555 says "It is RECOMMENDED that connection attempts be paced
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150-250 ms apart to balance human factors against network load." libcurl
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currently defaults to 200 ms. Firefox and Chrome currently default to 300 ms.
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.SH DEFAULT
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CURL_HET_DEFAULT (currently defined as 200L)
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.SH PROTOCOLS
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All except FILE
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.SH EXAMPLE
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.nf
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CURL *curl = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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curl_easy_setopt(curl, CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS, 300L);
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curl_easy_perform(curl);
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/* always cleanup */
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curl_easy_cleanup(curl);
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}
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.fi
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.SH AVAILABILITY
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Added in 7.59.0
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.SH RETURN VALUE
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Returns CURLE_OK
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.SH SEE ALSO
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.BR CURLOPT_CONNECTTIMEOUT_MS "(3), "
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.BR CURLOPT_TIMEOUT "(3), " CURLOPT_LOW_SPEED_LIMIT "(3), "
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