On Fedora I tried to access port 1521, so I opened the following port on my firewall:
$ sudo iptables -I INPUT -i eth0 -p tcp -m tcp --dport 1521 -j ACCEPT $ sudo service iptables save
I then tried to telnet to my inner IP (the IP that the router gave me) and got connection refused:
$ telnet 192.168.1.103 1521 Trying 192.168.1.103... telnet: connect to address 192.168.1.103: Connection refused
I then tried to telnet to my internet IP and didn't get any response:
$ telnet x.x.x.x 1521 Trying x.x.x.x...
As far as I can tell, I've opened my port on the router also, BTW, I also tried it with port 22 and got the same result.