🚀 go-pugleaf

"Peter Kirby" <peter.news@aworld.demon.co.uk> wrote in message
news:MPG.165c6c7b20e9b93c9896f2@news.demon.co.uk...
> I noticed this recently in iptraf. I don't know what game it is but it
> uses UDP and packets go from port 27005 to port 27005. This means that
> on any NAT based network I believe only 1 person could connect and play
> at once. That is unless the server has some fallback measure which uses
> a different port number, or allows the remote port to be different that
> the server port.

A NAT firewall/router should still able to track which packets go to which
machines, simply with the combination of incoming and outgoing port numbers
and their IP addresses. It is simply a matter of making the NAT software
smarter and able to track more things in its tables.

For example, you got an external IP (to the Internet) address attached to
the router, say n.n.n.n. It's got an internal IP address (to the LAN) of
x.x.x.1. There are two clients on the inside, say x.x.x.2, and x.x.x.3.  So
if the clients need to connect to port 27005 on the same server on the
Internet simultaneously, they would each select a random outgoing port
number and connect to port 27005 of x.x.x.1. The internal table would look
like this:

Outgoing                  Incoming
x.x.x.2:2000             x.x.x.1:27005
x.x.x.3:4500             x.x.x.1:27005

So as you can see even though both clients are hooking to the same IP and
incoming port on the NAT router, they have their own unique IP and outgoing
port numbers which the NAT software should be easily able to track.

The NAT router then regenerates the requests over the Internet for each of
the clients. It will then generate separate random outgoing ports for each
client and and connect to a server on incoming port 27005 on the internet.
It will have a separate table for the Internet side of the connection.

This should all work as long there isn't any connect backs from the outside
servers back to the clients in the LAN. But even that could be handled with
enough intelligence.

    Yousuf Khan