wcf p2p file transfering over internet

[C# Programming]

i m developing the desktop application in c# dotnet for p2p file transffering..I am using wcf for this ..I have seen many articles over this ,they run smoothly on local computer as usually,but my application is p2p over internet and should not limited to LAN.I have found a article "http://www.codeproject.com/Articles/37057/File-Transfer-using-WCF-and-Socket" .Its run smoothly sometime but not always..can anybody help me regarding this.I Have done this with webservies hosted on server where my data reaches first on server and then transfer to destination but this is not wat i need.I want to transfer p2p directly where data should not reaches on intermediate server..please help me regarding this..Thanks in advance