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- .\" generated by cd2nroff 0.1 from CURLOPT_SSL_ENABLE_ALPN.md
- .TH CURLOPT_SSL_ENABLE_ALPN 3 "2025-01-17" libcurl
- .SH NAME
- CURLOPT_SSL_ENABLE_ALPN \- Application Layer Protocol Negotiation
- .SH SYNOPSIS
- .nf
- #include <curl/curl.h>
- CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_ENABLE_ALPN, long npn);
- .fi
- .SH 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.
- .SH DEFAULT
- 1, enabled
- .SH PROTOCOLS
- This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.
- All TLS backends support this option.
- .SH EXAMPLE
- .nf
- 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);
- }
- }
- .fi
- .SH AVAILABILITY
- Added in curl 7.36.0
- .SH RETURN VALUE
- Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
- .SH SEE ALSO
- .BR CURLOPT_SSL_ENABLE_NPN (3),
- .BR CURLOPT_SSL_OPTIONS (3)
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