If you have an airport extreme, open the Airport Utility in your Applications Folder->Utilities Folder.
Click on the Network Tab and then look at the Port Settings box. You should have created a port setting rule to open those required ports. I named my rule WeatherCatServer. Click on the rule to highlight it and click edit to check the ports. It should look like the second image. This is the main reason why a static IP address assigned to your main computer is crucial, because if its IP address can float, then these rules of open ports are meaningless, regardless of the router you use, and the "server" function won't work. If you have a different brand router, the settings should be similar. I hope this helps,
dfw