As you can see my online game looks pretty nice (at least I think so and i know about the smily). But only people in my home network can play it, how come? I made my own server app with the host a server (hosted on port 1203) fuction, but only the computers in my network can play the game online and not somebody else...
90% sure that the port is blocked on your router or firewall.
If you have a firewall, such as Windows firewall, Norton or Zone Alarm - you need to enter those programs and find out how to unblock/port forward that port - which is 1203.
If you have a router, you'll probably need to port forward on there also - to find out how to do that, simply go to http://portforward.com/routers.htm - select your router and it will give you a guide on unblocking a port. You need to unblock 1203 TCP I think - however I do both TCP and UDP for no reason really
Also I have no idea whether ports can be unblocked on windows firewall - so if you have that, you may need to just disable it (it's a pain in the butt anyway). Hope that helped.
The Public and Private Port should be the same as the one that you're connecting on (I don't see any reason to change it), and the host IP is the network IP of the computer that's actually running the program.
I have that same problem, only people on my network can connect. I have gave my computer a static ip and then fowarded port 1203 to my computer and allowed port 1203 on the firewall.