client-server-router problem

Hello.

I start from describing my home network setup. I have a PC and two laptops at home all connected to internet by wireless router. Recently i started playing a bit wit java networking. I made a little client-server program that allows me to communicate between PC an a laptop. So so far so good.
The problem started when I try to connect to the server from outside. When i tried to connect with my PC fron my friends house but it didn't work. And I'm not sure why not. When i checked my IP on whatsmyip.com the IP nummber it gave my was different from the IP I have in my PC's internet settings. whatmyip.com tells me also that all computers at home have the same IP. So i presume it actually is IP of the router.
So my question would how can i connect with my PC from the outside of the LAN.

Thanks in advance

Looking into these might help,Have you forwarded/enabled port listening from your router for your specific host?
Did you use NAT-Virtual Servers,Port Triggering? or whats your Incoming IP Filtering Setup-possibly block? the best place that you can find most of your answers, is FAQ of Homeserver softwares !