[1.1.30] (solved) Not seeing NAT punches

[Hornwitser]

I tried hosting a public game from inside the client on my desktop, which is behind NAT. And then I had some friends try connect to it via the public server list. While doing this I was performing a packet capture to see the NatPunchRequest messages sent to my computer. But I didn't see any when they tried to connect and their connection attempts failed.

So I tried the reverse. They hosted a server a server behind NAT on their end and I tried to connect to it. In this case I could see NatPunchRequest packets being sent to ping pong servers with their IP and port, along with a ConnectionRequest to that IP and port, but ICMP answered with Destination unreachable on their end indicating no NAT punching had taken place.

Why doesn't the NAT punching work in this setup?

Edit: I figured out that the client is bugged and the server is also bugged.