Port 14567 UDP is the only port you have to open for Battlefield 1942. If you want to have your server listed on gamespy, you might also need to open the following ports. Allow TCP and UDP Ports 12203 Allow UDP Port 14690 Allow UDP Ports: 23000-23009 Allow UDP 22000 (This is only for LAN) # GameSpy Master Server UDP Heartbeat: Allow UDP Port 27900 # GameSpy Master Server List Request: Allow TCP Port 28900 It's also important to note that EA suggests DMZing your computer for Battlefield 1942.
Click the Firewall button near the left hand side of the page.