Airport extreme: ports closed even after port mapping

The Airport Extreme needs a Public IP address from your modem to be able to set up Port Mapping correctly, so it might be a good idea to first check to make sure that this is the case

Open AirPort Utility and click on the picture of the AirPort Extreme and a small window will appear with information about the AirPort.

Look for IP Address

Make sure that the IP address does NOT begin with 192.x, 10.x, or 172.x. If it does, then look down the settings in the window to see if you can find a setting for Status. Does Double NAT appear here?

If yes, what is the make and model number of the device that you call your modem?

Opening ports is more difficult without upnp support in the airport..

How are you checking the port is closed?

If other people have tried and failed to connect to your server.. what address are you giving them??

Is it publically routable address.. ?? Have people from outside your network.. using a terminal

telnet YourWANIPaddress 25565 (replace with the actual WAN IP and see if it works).

Telnet should make a connection to open port server.. if it fails get people to run ping and trace route to the WAN IP.

Make sure your ISP is not using CGNAT or some proxy servers.. they may not block ports but they might block incoming connections through their own setup.

No luck try what happens with the computer plugged directly to the internet.. no router at all.. if it then works.. get a new standard UPNP router.. it is just a lot easier.. Apple never bothered with gaming.