Manpages - CURLOPT_SSL_ENABLE_ALPN.3

CURLOPT_SSL_ENABLE_ALPN - Application Layer Protocol Negotiation

#include <curl/curl.h>

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

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.

1, enabled

HTTP

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

Added in 7.36.0

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

*CURLOPT_SSL_ENABLE_NPN*(3), *CURLOPT_SSL_OPTIONS*(3),