The call is not connected when callee answers the call. The caller hears ring back tone
On a machine which Brekeke SIP Server is running, capture the UDP packet using a network analyzer, such as Ethereal, and check if SIP sequences are correct.
When NAT traversal is in use (when you have communication over mutual networks), please refer to ”Brekeke SIP Server Administrator’s guide – NAT traversal” for more details.