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natupnphole-punchingstun

UDP/TCP hole punching vs UPnP vs STUN vs?

I'm trying to make a P2P Program and need help with getting through the NAT of the clients. I'm curious about:

  1. The drawbacks/benefits of the three methods i listed and which else exists?
  2. How many routers support which methods?
  3. Which methods are commonly used by the big companies? (BitTorrent, TeamViewer,...)
Solution

  • UPnP requires software support in your router. Even when routers have it, it's sometimes turned off due to security concerns.

    STUN uses a simple public server to detect the presence of NAT and the real IP addresses. This is useful for other, higher-level protocols that do the useful work.

    Hole punching is a simple technique to connect two computers. It requires a 3rd public computer to communicate between the 2 computers behind NAT. You could run your own server with a custom protocol, our you could use STUN and existing STUN servers. (Only a few packets are needed for setup, the rest are peer-to-peer).

    Of course, some NAT firewalls are incompatible with the above, so you may need a custom protocol. Bittorrent does this: they use different techniques depending on which clients are behind firewalls and whatnot.