CURLOPT_SSL_ENABLE_ALPN3

Usage

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_ENABLE_ALPN, long npn);

Overview

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

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. only

All TLS backends support this option.

Examples

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

Return value

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).