libssh2_keepalive_config man page
libssh2_keepalive_config — short function description
void libssh2_keepalive_config(LIBSSH2_SESSION *session, int want_reply, unsigned interval);
Set how often keepalive messages should be sent. want_reply indicates whether the keepalive messages should request a response from the server. interval is number of seconds that can pass without any I/O, use 0 (the default) to disable keepalives. To avoid some busy-loop corner-cases, if you specify an interval of 1 it will be treated as 2.
Note that non-blocking applications are responsible for sending the keepalive messages using libssh2_keepalive_send(3).
Added in libssh2 1.2.5