> There does exist at least one NAT hole-punching technique that can traverse two NATs with no central server using ICMP-based holepunching and UDP. Obviously,

> There does exist at least one NAT hole-punching technique that can traverse two NATs with no central server using ICMP-based holepunching and UDP. Obviously, like all hole punching techniques, it only works on certain kinds of NATs, and firewalls can kill it. I think you're referring to this? Clever hack indeed. https://github.com/samyk/pwnat https://github.com/samyk/pwnat