I developed a video chat program in VB using the UDP protocol. However, when trying to contact my friend nothing happens. When I ping his computer it says "host unreachable".
Can his ISP be using Network address translation? or maybe have UDP ports 138,139 closed or maybe doesn't trust the custom app sending the packet? If I can't ping the other computer, should I just forget about this or is there something else I can try? I don't think changing the protocol to TCPIP will have any effect, do you? Thanks for your help.