You will need to forward port 28100 then and allow it through your computer's firewall.
Both the application and the port.
28000*
How do I do that?
http://portforward.com/english/routers/port_forwarding/
Tell me what information to put in the new rule?
The port forward rule would forward the port to your computer's LAN IP address (read here) and would allow port 28100, since that's what you changed your server port to.
Also, what is 28000 mean?