Sun Aug 18 23:42:45 EDT 2013


I finally get it.

You probably need a STUN server when placing a sip call if *you* are
behind a masquerading firewall.  The reason is that the SIP headers
contain *your* IP, not the IP of the masquerading server.

A SIP client uses a STUN server to obtain its masquerading / outgoing
IP, so it can pass the address in SIP headers to other parties.

CSipSimple uses stun.counterpath.com