You have to use the public IP address in the Via header and in the contact header. Better would be to use a SIP proxy which rewrites the messages (e.g. ser and nathelper module) accordingly to the source address:port of the incoming messages and use a symmetric client (send and receive RTP on the same port). Usually iptel.org should have the nathelper module enabled and this should work. More information on this topic is also available on www.voip-info.org. ->NAT traversal Klaus -----Original Message----- From: Santosh Subramanian, Noida [mailto:Santoshsu@noida.hcltech.com] Sent: Thu 11.12.2003 09:02 To: &#39;serusers(a)lists.iptel.org&#39; Cc: Subject: [Serusers] How to Register..? Hi, I have a client program , which will send REGISTER request to the proxy server and get back the response either "200 ok" or "401 unauthorized". I'm running SER proxy server in my local network and it is giving me "401 unauthorized". no problem in that. Now I'm trying to contact iptel.org with that program. Its since I'm running my program behind the firewall, the address and port (195.37.77.101:5060) is opened for me both ways. So my request should have reached iptel.org. Problem is, no response from iptel.org. can anyone working behind firewall send me the message format for REGISTER request. I've attached mine along with this mail.. kindly let me know if anything is wrong. I'm not able to proceed from this point. Kind Regards, Santhosh.S My Register Request: ===================== REGISTER sip:san.iptel.org:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.14.56:5060;branch=z9hG4bK2952839661;rport From: san <sip:san@iptel.org>;tag=946143070 To: san <sip:san@iptel.org> Call-ID: 320799555(a)195.37.77.101 CSeq: 1 REGISTER Contact: san <sip:san@192.168.14.56:5060> max-forwards: 70 user-agent: oSIP-ua/0.8.1 expires: 3600 Content-Length: 0 where username is "san" My call flow shld. be: san SER Sip Server | | | REGISTER F1 | |------------------------------>| | 401 Unauthorized F2 | |<------------------------------| | REGISTER F3 | |------------------------------>| | 200 OK F4 | |<------------------------------| | | _______________________________________________ Serusers mailing list serusers(a)lists.iptel.org http://lists.iptel.org/mailman/listinfo/serusers