Accessing Computer using Internet through NAT

[DigiRev]

Some programs attempt to use uPnP but it fails most of the time because every router is different and most have it turned off as was already said.

I would suggest either opening the ports manually or re-writing your code and creating a central server and all data goes through that server program.

This is how most big servers like Yahoo and MSN work because they have the speed and can afford the bandwidth.

It might slow things down for you, but it would work. You could run it from a computer that's not behind a NAT/router, or you could just setup the router manually on that computer once and you would be done.

Also, have you tried being the server, and have your friend connect to you?

[dilettante]

The use of NAT offers some real advantages, but it also imposes a somewhat asymmetric model on top of normal Internet operation.

In many ways it's like using a cell phone instead of a walkie-talkie. True walkie-talkies can communicate with each other freely, with no intermediary. Using NAT tends to block this sort of interaction for PCs.

Things like most messenger programs work more like a cell phone that has to work through an intermediary service to call somebody else.

NAT lets PCs connect outward fairly freely to hosts on the public Internet. Connecting inward through NAT into another private network is another thing altogether. The whole point of private networks and private addresses is that they are not routable. There is no way to get from the public network into a private network with standard routing. Some other mechanism (like port mapping) is needed, whether done manually or with uPnP or whatever.