Hi, I have “30 second-then-hangup” problem. I have traced the problem, and turn out that the server keeps sending ACK to SIP Client local IP Address (it is behind the NAT). Is it a misconfigure in FS? I notice that in SDP received from SIP Client the rtcp port is followed by SIP Client local IP address. Is it right or not? Here is the SIP trace result: recv 738 bytes from udp/[118.xxx.xxx.xxx]:6900 at 10:21:33.992037: ------------------------------------------------------------------------ SIP/2.0 200 OK Via: SIP/2.0/UDP 192.168.1.150:57699 ;rport=57699;branch=z9hG4bK4Q9KyFrDr24gc From: "400001" <sip:400001@180.xxx.xxx.xxx>;tag=59etrFg3F0pvg To: <sip:400002@118.xxx.xxx.xxx:6900;line=b1bb925d6ab814e>;tag=189404928 Call-ID: ea145392-ddb9-1231-9c95-94de80208578 CSeq: 53085761 INVITE Contact: <sip:linphone.android@192.168.8.47:6900> Content-Type: application/sdp User-Agent: LinphoneAndroid/0.3.7 (eXosip2/3.6.0) Content-Length: 260 v=0 o=400002 1335 3400 IN IP4 118.xxx.xxx.xxx s=Talk c=IN IP4 118.xxx.xxx.xxx b=AS:380 t=0 0 m=audio 7078 RTP/AVP 98 101 a=rtpmap:98 speex/8000 a=fmtp:98 vbr=on a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-11 a=rtcp:7079 IN IP4 192.168.8.47 ------------------------------------------------------------------------ nta.c:3201 agent_recv_response() nta: received 200 OK for INVITE (53085761) nta.c:3264 agent_recv_response() nta: 200 OK is going to a transaction send 434 bytes to udp/[192.168.8.47]:6900 at 10:21:33.992228: ------------------------------------------------------------------------ ACK sip:linphone.android@192.168.8.47:6900 SIP/2.0 Via: SIP/2.0/UDP 180.xxx.xxx.xxx:57699;rport;branch=z9hG4bK502c0a9gNBU3Q Max-Forwards: 70 From: "400001" <sip:400001@180.xxx.xxx.xxx>;tag=59etrFg3F0pvg To: <sip:400002@118.xxx.xxx.xxx:6900;line=b1bb925d6ab814e>;tag=189404928 Call-ID: ea145392-ddb9-1231-9c95-94de80208578 CSeq: 53085761 ACK Contact: <sip:mod_sofia@180.xxx.xxx.xxx:57699> Content-Length: 0 ------------------------------------------------------------------------ nta.c:8169 outgoing_send() nta: resent ACK (53085761) to UDP/ 192.168.8.47:6900 Thanks, Regards Donny