I'm trying to add networking functionality to my game. I want any user to be able to host the game, and anyone to be able to connect as a client. The client sends info to the host about their player's position, etc. When the host receives a message, it validates it and then broadcasts it to its other clients. I will primarily be dealing with UDP, but will also need TCP for chat & lobby stuff.

The problem is that I can't seem to get a packet sent from the client to the host or the other way around without enabling port forwarding on my router. But I don't think this is necessary. I believe the reason I need port forwarding is because I want to send a packet from 1 computer on a LAN to another computer on a different LAN, but neither of them have a global ip address since they're in a LAN. So really, I can only send packets targeting the other network's router, which must forward it on to the machine I want to reach. So how can I do this without port forwarding? Somehow a web server can communicate with my computer, which doesn't have a global ip, without port forwarding. And I've played plenty of multi-player games that don't require me to enable port forwarding. So it must be possible.

Btw, I'm using SDL_Net. I don't think this will change anything though.