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Hello all members of the forum,

I am currently trying to do p2p between a private ip form mobile phone which is behind ISP Symmetric NAT with a public ip using java.For this also tired Stun servers, but the stun server only just detects the type of the NAT and can't retrieve the port mapped information.Interestingly i also saw that google webRTC easily do it.So is it possible to communicate between my 2 ip addresses? Please give me some clear solution about what is possible in that case.Also if you have ever seen any nice running project similar to mine then please share the link. Thanks.

  • look at this perhaps? http://stackoverflow.com/questions/5077720/behind-nat-to-behind-nat-connection?rq=1 – aCuria Aug 28 '13 at 07:29

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Symmetric NATs are very special case in P2P connection. They map public port randomely for each outgoing packets. Read this article Symmetric NAT and It's problem .As you mentioned, you did used STUN. But it only maps public/external ip and port. Try using TURN servers. TURN servers are designed to handle, such cases where STUN fail. I am not an expert in webrtc, but I am using PJNATH. This library implements ICE stack, which use both STUN and TURN protocols to establish a P2P channel.