Hi Benny, I have running pjstun_client to get the NAT type. The result was "NAT successfully detected as Blocked", but UDP isn't completely blocked (only STUN Port 3479) and one STUN response have reached pjsip (Stun Test I). Doing the same test with WinStun the result was "NAT with Independend Mapping and Port Dependent Filter...". In attachment you can find the Wireshark Trace of the STUN packets (pjsip and winstun), the pjsip logging and the result of WinStun. One difference I have found is that pjsip sends a STUN request to an alternate STUN Server to port 3479 (given in STUN response: CHANGED_ADDRESS) but WinStun always uses 3478. What's wrong? Best regards, Helmut Wolf -------------- next part -------------- A non-text attachment was scrubbed... Name: stun test.zip Type: application/x-zip-compressed Size: 8341 bytes Desc: not available Url : http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/attachments/20080421/6e945dab/attachment.bin