(Moslty for my own reference.) If you’re trying to download a patch of World of Warcraft, have an Apple AirPort base station, and are getting the error “Your computer appears to be behind a firewall”, these are the steps I was able to use to get it to work.
- Open up AirPort Utility.
- Click on your AirPort station and select “Manual Setup” from the “Base Station Menu” (or ⌘-L).
- Click “Advanced”, and “Port Mapping”.
- Click the “+” button.
- Enter “3724,6112,6881-6999” into the Public and Private UDP and TCP ports, and enter your own IP address into “Private IP Address”. (To get your IP address, open up System Preferences, go to Network, click on your AirPort station, click “Advanced”, then “TCP/IP”. Your IP address is what’s listed as IPv4 Address.)
- Click “Continue”, and name it whatever you want, then “Done”.
The Blizzard Downloader should turn green. If it doesn’t, try restarting the app.