UDP Hole Punching Java Example

Question

I want to do UDP Hole Punching with two clients with the help of a server with a static IP. The server waits for the two clients on port 7070 and 7071. After that it sends t

Answer 1

You rightly use a rendezvous server to inform each node of the others IP / port based on the UDP connection. However using the public IP and port which is the combination which will is obtained by the connection as you have, means that in scenarios where both hosts exist on the same private network hairpin translation is required by the NAT which is sometimes not supported.

To remedy this you can send the IP and port your node believes itself to have in the message to the server (private ip / port) and include this in the information each node receives on the other. Then attempt a connection on both the public combination (the one you are using) and the one I just mentioned and just use the first one which is successfully established.