=Events=
* [http://wiki.freeswitch.org/wiki/Mod_event_socket mod event socket]
* [http://wiki.freeswitch.org/wiki/Event_List event list]
* [http://wiki.freeswitch.org/wiki/Hangup_Causes hangup causes]: may be used to control 呼叫转移
=RTP=
* [http://www.siptutorial.net/RTP/index.html RTP]: a good short tutorial