As you can see, the server only has a single IP address, 192.168.12.137. This IP address is a "private" or "non-routable" IP address for use in private, closed networks like your own. The public IP address you're using to access the Internet (the one displayed if you visit a site like http://whatismyipaddress.com
) belongs to the SonicWall.
If you want a service on the CentOS server to become available to outside users accessing the public IP address of the SonicWall, you need to tell the firewall in the router to perform "port forwarding" for the service in question.
You say there are rules in the firewall related to a computer you previously had on your network. You may be able to simply change the IP address in those rules, pointing it to your CentOS server instead.