Have you got a WiFi Router? If you can, log into the router. See if you can find the IP address of the router (usually on the back of the router itself) Then, type that into your browser and log in. The default username is: admin and the password default is: password
Then you should be able to find a Firewall menu (if its turned on in your router). From there, you can add a service. Title it with your game, and the LAN Users IP Address is your own IP. Then select the WAN Users as Any. That should allow it to work.
If you know what ports your game uses to connect to other users, go to the Service's tab in your router and set up a service, with the same title as the Firewall Service you set up before. That will only open the ports used by your game, so it's safer
I'm pretty sure thats right, or I completley missed the point...hope not

PM if you need more help