Hi,
Does anyone know why file sharing applications like Emule, EDonkey, Bittorrent require port forwarding when used over a NATted network? I understand the principle that the incoming connection needs to be requirected to a specific internal (LAN) IP address to get to the correct client and I have successfully set this up on many occassions... but then I started thinking about web (HTTP Port 80/ 443) traffic and how that requests of this nature can be routed back to it's original client all over the same port, over NAT, and without the need for port forwarding. I'm assuming that the originating non-routable (LAN) address must be stored in each packet throughout it's life so it knows where to go when it gets back to it's native firewall on the way back in.
So I guess what I'm asking is 'What is the difference between this standard Web traffic and traffic generated by these file sharing programs'? Couldn't file sharing programs employ the same technology to reduce the set-up overhead and remove the requirement for complex port forwarding setups?
Any thoughts and comments appreciated.
Edd