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.TH CURLOPT_TCP_FASTOPEN 3 "November 04, 2020" "libcurl 7.74.0" "curl_easy_setopt options"

.SH NAME
CURLOPT_TCP_FASTOPEN \- enable TCP Fast Open
.SH SYNOPSIS
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_FASTOPEN, long enable);
.SH DESCRIPTION
Pass a long as parameter set to 1L to enable or 0 to disable.

TCP Fast Open (RFC7413) is a mechanism that allows data to be carried in the
SYN and SYN-ACK packets and consumed by the receiving end during the initial
connection handshake, saving up to one full round-trip time (RTT).
.SH DEFAULT
0
.SH PROTOCOLS
All
.SH EXAMPLE
.nf
CURL *curl = curl_easy_init();
if(curl) {
  curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
  curl_easy_setopt(curl, CURLOPT_TCP_FASTOPEN, 1L);
  curl_easy_perform(curl);
}
.fi
.SH AVAILABILITY
Added in 7.49.0. This option is currently only supported on Linux and  OS X
El Capitan.
.SH RETURN VALUE
Returns CURLE_OK if fast open is supported by the operating system, otherwise
returns CURLE_NOT_BUILT_IN.