Most consumer Firewalls and Routers allow almost all outgoing network traffic. However, many are starting to cramp down on outgoing network traffic to help protect users from spyware that transmits data from your computer to another site without your consent.

If you have configured your Firewall and Router as described in the previous two sections but are still having problems connecting to games, it might be because your Firewall and/or Router is blocking some of your outgoing network traffic. In this case, you may need to open some specific network ports for outgoing traffic to reach Gamespy. Specifically, you may need to

Allow OUTGOING traffic on:

UDP 27900
UDP 29910
TCP 29900
TCP 29901
TCP 29920
UDP 27901
TCP 6667
TCP 28910

Remember that you may need to do this for BOTH your Software Firewall and your Router.