4 ms·

Firewall traversal for mediated PtP through basic stateful firewalls is simple - both sides start sending UDP packets to each other and outgoing packets open ho

Firewall traversal for mediated PtP through basic stateful firewalls is simple - both sides start sending UDP packets to each other and outgoing packets open hole in firewall for incoming packets. The same approach does not work reliably with NAT, mainly because you do not know translated port numbers. It also may fail if both sides are behind the same NAT, as NAT pinning is sometimes not implemented.

fomine3 5y ago
So is UDP hole punching the only modern way to traverse firewall?
- can16358p 5y ago
  Which is a very hacky way. I wouldn't rely on it for anything serious as it might break at any time.
  - zajio1am 5y ago
    Why? It seems like simple, reliable and trivial. It is not hacky, it is essentially how stateful outgoing-only firewall is supposed to work for UDP.