I have an interesting problem for you.
I have a few ports that I opened up. On my router and I allowed then on my firewall too with sudo ufw allow 30999.
But still the application which would use it, for example ssh server, still can't. And if I go to an open port checker site it still says that the port is closed.
So I ran out of options. I did the usual. I restarted and stuff like that, but nothing seems to help.
This is an Kubuntu 12.04 32 Bit. updated machine. Wireless connection with a Sky Broadband router in the UK.