Set preferred tls/ssl version
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLVERSION, long version);
Pass a long as parameter to control which version of SSL/TLS to attempt to use.
Use one of the available defines for this purpose. The available options are:
The default action. This will attempt to figure out the remote SSL protocol version, i.e. either SSLv3 or TLSv1
TLSv1.0 (Added in 7.34.0)
TLSv1.1 (Added in 7.34.0)
TLSv1.2 (Added in 7.34.0)
All TLS based protocols: HTTPS, FTPS, IMAPS, POP3, SMTPS etc.
SSLv2 is disabled by default since 7.18.1
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.