curl-w32/docs/libcurl/opts/CURLOPT_SSL_ENABLE_ALPN.md

c	SPDX-License-Identifier	Title	Section	Source	See-also
Copyright (C) Daniel Stenberg, <daniel.se>, et al.	curl	CURLOPT_SSL_ENABLE_ALPN	3	libcurl	CURLOPT_SSL_ENABLE_NPN (3) CURLOPT_SSL_OPTIONS (3)

NAME

CURLOPT_SSL_ENABLE_ALPN - Application Layer Protocol Negotiation

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_ENABLE_ALPN, long npn);

DESCRIPTION

Pass a long as parameter, 0 or 1 where 1 is for enable and 0 for disable. This option enables/disables ALPN in the SSL handshake (if the SSL backend libcurl is built to use supports it), which can be used to negotiate http2.

DEFAULT

1, enabled

PROTOCOLS

HTTP

EXAMPLE

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_SSL_ENABLE_ALPN, 0L);
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

AVAILABILITY

Added in 7.36.0

RETURN VALUE

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.