## NAME

CURLOPT_TCP_FASTOPEN - enable TCP Fast Open

## SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_FASTOPEN, long enable);

## DESCRIPTION

Pass a long as parameter set to 1 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).

## DEFAULT

0

## PROTOCOLS

All

## EXAMPLE

TODO

## AVAILABILITY

Added in 7.49.0. This option is currently only supported on Linux and OS X El Capitan.

## RETURN VALUE

Returns CURLE_OK if fast open is supported by the operating system, otherwise returns CURLE_NOT_BUILT_IN.

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