Set tcp keep-alive interval
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_KEEPINTVL, long interval);
Pass a long. Sets the interval, in seconds, that the operating system will wait between sending keepalive probes. Not all operating systems support this option. (Added in 7.25.0)
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.