When is port forwarding necessary?

Question

I\'ve been investigating networking for use in a two-player game I\'m writing, and I\'m still not clear on when a device must have a port forwarded in order to communicate w

Answer 1

There is reason why Skype don't (not always) need manual setting of port forwarding:

When you install Skype, a port above 1024 is chosen at random as the port for incoming connections. You can configure Skype to use a different port for incoming connections if you wish, but if you do, you must open the alternative port manually.

If the port chosen for incoming connections becomes unavailable, by default ports 80 and 443 will be used as alternatives. If another application (such as Apache HTTP server or IIS) uses these ports, you can either configure the application to use other ports, or you can configure Skype to not use these ports.

Port forwarding is must if you host a server. You can use same technique as Skype... I am not sure if there is any other option...