I have a cable modem linked to a router which then linked to 2 computers, everything works fine and i can do everything you can do on lan. BUT, i been working on a program that can connect over the net to my friends computer, when he is running the server, he dosnt have a router and the ip he got from www.watismyip.com is the right one and i can connect to him, THE PROBLEM IS when he tryed to conecte to me, i dont seem to know which ip im using to identify on the net, there were 3 ips i found ont he net, and 2 more for my LAN, he tried to connect to every ip i can tell him and nothing seem to work, can anyone tell me how do i find out what my ip is over the net so my friend can connect to me

Your router takes over your Internet IP address assigned by your ISP. If you access the routers IP address on your local network (LAN address 192.168.1.1 normally), it will show you what its Internet or WAN IP address is. This is the IP address all systems on the Internet must use to talk to your local network. When you access a server's Internet IP address, the router recognizes the address is not in the 199.168.xxx.xxx range and routes it to the Internet using its WAN or Internet address assigned by your ISP, and then routes responses back to the sending IP address on the LAN. However, when a system behind the router tries to act as a server, the router does not know what local system to send the inbound requests to. In fact, if the router has an inbound firewall, it will block the request. To get around this, most routers can be configured to Forward specific External port requests (TCP and/or UDP) to a specific local IP address. To use this type of function the router must be given a specific local IP address outside of its dynamic assignment range, hence that system must be given a specific local IP address (system must be setup to use a specific IP address and not get one assigned dynamically by the DCHP router). Once this is done, all incoming traffic to these ports will be redirected to the "server". This gets a little tricky and you have to know the ports involved. Another way, is if they router supports a DMZ Host. You again setup the "server" with a fixed local IP address, and then set that IP address as the DMZ Host. This system is then exposed to the internet as if it has your routers WAN IP address. Local LAN machines must know to address this "server" by it local IP address, not your public IP address. As most DSL/Cable IP addresses are dynamically assigned by your ISP (unless you are paying for a fixed IP address), you have to have a way to determine from the router what your current public IP address is, so your "server" can provide it to external users.