I have developed a Java server which listens for UDP packets which come from mobile devices. At the moment, it works correctly if I run my Server on my windows PC. I can receive and respond to the UDP packets sent from my phone (over 3g, not wifi).

However, I am trying to run the Server on a different computer which I found lying around my house. I have basically done a clean install of Ubuntu Server edition, updated it, installed the java run time environment and configured port forwarding to allow connections on the appropriate port. I have also tried to disable the firewall.

The problem is, it doesn't appear as if the server is receiving any packets and I've exhausted my brain thinking on how to solve/debug the problem. Can anyone suggest to me what the problem might be? or more likely something I can do to help me find out more information about what is going wrong.