[zhrance]

Hey, how come I can connect to some games, but not others?
How come I can connect to ranked games, but not custom games (or vice versa)?
I have all of my ports open. I don't have antivirus/firewall problems. What's wrong?

It's all about peer-to-peer connections.

Supreme Commander uses a peer-to-peer networking scheme in order to play games via GPGnet. This setup is common for real-time strategy games, where there is a definite beginning and end to each game, as opposed to a server-client game like an MMO or a first-person shooter, where players can connect to a centralized server and drop-in any time.

Peer-to-peer games have more complex, stringent networking requirements, because not only are you connecting to another player's computer, all the players involved a game must have connections to all the other players at the same time.

It's Not You, It's Them. Maybe.

There's an important point here that shouldn't be missed -- while you and another player can both be able to connect to GPGnet, you may have problems connecting to each other. You might be able to connect to some games but not others.

The problem is that peer-to-peer connection requirement.

Just because YOU have no issues doesn't mean YOUR OPPONENT doesn't have issues. You may hang on connection because the other guy's firewall won't allow the connection.

The problem can be on either side. All you can do is ensure that you don't have antivirus or network management software blocking the game and GPGnet, and if you have a firewall, that the proper ports are open. And encourage your friends to examine their networks, too.

What ports should be open in order to connect to play Supreme Commander online through GPGnet?

GPGnet and Supreme Commander require the following ports to be open:

* Ports 30350 and 30351 opened for UDP traffic, to allow for GPGnet logins
* Port 9103 open for UDP traffic, to allow for GPGnet-brokered matchmaking
* Ports 6112 open to UDP traffic, to allow for SupCom gameplay. This port is among the most common ports used by online multiplayer games of all kinds.

There are online tests to see if ports are open:

* A good test for port 6112 is at Relic Forums - DoW multiplayer network tester (BACK UP AND RUNNING)
* A more general-purpose test, called Shields Up!, can be found at Home of Gibson Research Corporation

Router, firewall, antivirus and networking management software can all hinder gameplay. For more information on firewalls and anti-virus software, perform knowledge base keyword searches for FIREWALL and ANTIVIRUS.