about working on network

thanx Paul. now I have another question(if you dont mind).
again - it's not my field (yet) so Ihave almost no idea where to start.

my applications work well using TcpClient and Listener on the same
computer.

I moved one of them to another computer and it doesnt. do you have an
idea about the cause for this.
(Im sure about the ip and the port ,and I've pinged between then)
thanx again