Re: Cannot play with roommate on same wifi

If you have to forward ports to a local ip then there's definitely something wrong with either your network or the games servers. 

Opening ports for outgoing connections is fair enough, but that's rarely needed. 

Network Address Translation (NAT) should find a free port on your router and translate your local source address to that NAT address.

By forwarding incoming ports to a local ip you limit communication on that port to that local device. 

Multiple people would theoretically still be able to play from the same network as forwarding shouldn't be needed and NAT should translate outgoing request to the game server with a random source port mapped to the local device.

The only reason why forwarding would work is because either the server or the local request uses the destination (remote) port as the source (local) port.

If NAT has failed and two local devices expect game data on the same port, then that would explain why you get kicked when playing together.