/* Sets the "probe interval" for 'fsm' to 'probe_interval', in milliseconds.
* If this is zero, it disables the connection keepalive feature. If it is
* nonzero, then if the interval passes while 'fsm' is connected and without
/* Sets the "probe interval" for 'fsm' to 'probe_interval', in milliseconds.
* If this is zero, it disables the connection keepalive feature. If it is
* nonzero, then if the interval passes while 'fsm' is connected and without