[Freeswitch-users] ESL asynchronous use

I'm trying to figure out asynchronous use of the ESL (from C). If I call esl_connect_timeout with a timeout of 0, what happens if the connection is not made immediately? Is there some callback function indicating success/failure? If the esl connection is lost (FreeSwitch crashes), is there a callback function indicating the lost connection? Or do I need to issue a status/keepalive to ensure function succeeds? Looking a bit at the esl.c code I'm wondering if the above are synchronous only.(polling for status)