4 ms·

https://en.wikipedia.org/wiki/Hole_punching https://en.wikipedia.org/wiki/Hole_punching tada.

• MichaelGG 13y ago
  Yeah that's not a general solution, that's just exploiting problems in particular NAT implementations.
  • mparlane 13y ago
    Skype did just fine with it.
    • MichaelGG 13y ago
      Incorrect. Skype relays media via other users when two users cannot directly connect. So if you and I are behind proper NATs, and no negotiation works, then we agree on a nearby (super?)node that is accessible, and relay media through there. Hole punching _can_ work, but again, it's exploiting implementation quirks in NAT devices and isn't a general solution (though it might do pretty well). The only standard way (AFAIK) to open up NAT is via UPNP, which the client software (and NAT device) needs to support. The client then talks to the NAT device and tells it to port forward. It seems pretty common nowaday, and is more elegant and secure than the hacky "poke around and see what works" implementations.
      • mparlane 13y ago
        http://www.h-online.com/security/features/How-Skype-Co-get-round-firewalls-747197.html http://www.h-online.com/security/features/How-Skype-Co-get-r... Note the date, things are very different now.