Hi. I made a program for tcp chat but I'm really confused with which IP to use. I can send a message to myself by sending a message to a local IP such as 127.0.0.1 or 192.168.1.100. When I tried with my external IP (the one from whatsmyip.com) I get a socket exception: The requested address is not valid in its context. In order to chat to a friend what IP does he have to give me, and if it's the external how do I get the program to work?