CURLOPT_TCP_KEEPALIVE

CURLOPT_TCP_KEEPALIVE is one of the accepted parameters for curl_setopt parameter #2.

CURLOPT_TCP_KEEPALIVE — 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 and CURLOPT_TCP_KEEPINTVL options, provided the operating system supports them. If set to 0 (default) keepalive probes are disabled. Available as of cURL 7.25.0

CURLOPT_TCP_KEEPALIVE = 213;