I spent 2 years on a cross platform p2p protocol with features borrowed from GameCom, RakNet, Zoidcom and the Torque Network Library (TNL). I failed, largely d

I spent 2 years on a cross platform p2p protocol with features borrowed from GameCom, RakNet, Zoidcom and the Torque Network Library (TNL). I failed, largely due to the complexity of overcoming NAT. This was before ZeroMQ and other libs made it easy to emulate TCP traffic on top of UDP (which IMHO is the way it should have worked in the first place). What concerns me most is that IPv6 supports NAT and so I have a feeling that we will be living with it for decades to come (effectively making large swaths of the population second class citizens, as they will perceive the internet as download-only). Does anyone know of a library that universally overcomes NAT, using STUN/UPnP/NAT-PMP and other techniques where necessary? Ideally it would work by handling the handshake and return a standard UDP port that "just works", giving the app a globally accessible public port.