After two days of googling and searching askubuntu i decided to start a thread.
Here's my problem:
I recently exchanged my server (running Lubuntu 12.04 with ssh service and a game service) for a newer one (running Lubuntu 16.04). The network card stays the same, I built it in the new server. After setting up the new server with those two services I could only connect from inside the LAN. Everytime I tried connecting with my mobile data the connection timed out. GRC's ShieldsUP! shows the two ports i use as Stealth, other ports as Closed.
Here's what I've tried:
- Connecting my old server again - both services worked, ShieldsUP shows the ports as Open, so Port forwarding and DNS resolving can't be the problem.
- disabling ufw (is there another sort of firewall which could be blocking ports?)
- enabling ufw and allowing the Ports