CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_KEEPALIVE, long probe);
Pass a long. If set to 1, TCP keepalive probes will be sent. The delay and frequency of these probes can be controlled by the CURLOPT_TCP_KEEPIDLE(3) and CURLOPT_TCP_KEEPINTVL(3) options, provided the operating system supports them. Set to 0 (default behavior) to disable keepalive probes
Added in 7.25.0
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.