View Full Version : Multiplayer ports confusing??

03-26-2012, 03:26 PM
How is it that some multiplayer games are easy to play in multiplayer like for instance:
1. League of legends
2. Battlefield 3
3. Counter-strike
4. Team Fortress 2
5. Left 4 Dead 1-2
6. Mass Effect 3
7. Crysis 2

but games like
1. Assassins Creed brotherhood/revelations
2. Grand theft auto IV
3. Modern Warfare 2-3

Are very strict about which ports are open, and if they aren't open you cannot play multiplayer(or very difficult to join). I can't figure out to open mine even after reading thousands of guide and tips, they just doesn't open.

Why does it differ so much?

03-26-2012, 03:48 PM
Well... how to put it...

For starters, your router will by default be 100% fine sending out information on any port whatsoever. Whenever you send out a request on that port, it usually accepts that information coming back so long as the sender is identified as the same person you sent the original request out to.

The issue is when you want to host a game. Hosting a game will require people to connect to your computer through one of these ports, but here's the problem; You did not send out a request on that port, you will randomly be receiving an "I want to connect!" request on that port. You have no method of knowing if this is an innocent game client wanting to play the same game as you, or a hacker attempting to cause a buffer overflow on that port, and using a new exploit, possibly gain elevated access to your system.

Now that you understand why Ports are not opened by default: Why are some games harder to JOIN? Because you're going to be sending out requests to join a server, so the incomming traffic won't be blocked, what's the real problem?

Well there's 2 ways this can be a problem: One is if the game is coded to make use of P2P networking; which is where a client can send data directly to another client without first going through the server, the server has dished out the IP addresses to all the clients. It's a rather uncommon tactic, but I've seen it.

The other thing is if the game is designed to handle host-cancelling. Meaning, if the host leaves the game, can the game designate a new host: In that case, even someone who joined originally needs to have the ports open so that if they get chosen as the host, they can host the game. This is far more common, and is probably what you see with MW2 and 3. (Can't vouch for the other titles)