NetPlay failed to connect to server

[MasterofGaming06]

I was playing Melee with my friend, and when I tried to connect to him via Dolphin, it came up with something like
Failed to Connect to Server. Could not communicate with Host.

Does anyone know why this is happening? It doesn't happen to them when they try to connect to me...

[JMC47]

It's likely an issue with trying to automatically get the ports forwarded. They could try manually port-forwarding.