CURLOPT_SSL_ENABLE_ALPN(3)                            Library Functions Manual

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
       All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

       All TLS backends support this option.

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.

SEE ALSO
       CURLOPT_SSL_ENABLE_NPN(3), CURLOPT_SSL_OPTIONS(3)

libcurl                          April 26 2024      CURLOPT_SSL_ENABLE_ALPN(3)