[Serusers] Is STUN protocol usable behind firewall?

[wangji]

Hi all,
    In my test environment there are a firewall between SER server and SIP terminal(But I am not sure). I think so because in this envirmonent SJPhone can not register to SER server (I use ethereal on SER server and can't find register packets from SJPHONE). I had tested SJPHONE behind a NAT created by cisco router and success. So I think that thing is a firewall. 
   Today I test X-Lite in the same environment with same setting but it works. I get the UDP packet by ethereal. I find it send packet to xtunnel.xten.net port 3478/3479. These ports are used by STUN protocol. I would why it works.
  Attached file can be open by ethereal.  In the file no reponse register is sent by SJPhone and those success is sent by X-Lite



Br,
Wangji
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