[gameprogrammer] Re: TCP/IP Problem: NAT

On Fri, 2004-11-19 at 12:47, Chris Nystrom wrote:
> I am creating a general purpose gaming platform by basically
> controlling SDL remotely with RPC calls.
> 
> This may be an obvious question, but I have checked the TCP/IP
> programming, and Sockets programming FAQs and done some google
> searches and still don't see it.
> 
> How do you socket progrmming with a machine behind a NAT ?
> 
> My application basically works like X-Windows does: it starts up a
> server (an SDL engine that listens for RPC calls) and then it makes a
> call to another machine to to start up a process that does actual work
> and communicates back to the original machine.
> 
> However, even if I passed the IP address of the NAT machine if would
> not be of any use to the other machine, but I am sure there must be a
> way to do this, as X-Windows handles it with no problems.

Hi Chris, how's it going?

This problem has no solution. NAT is designed to hide all the boxes on
one side of the box behind a single IP address. The result is that they
cannot be addressed from the other side of the box. NATs can be
configured to send requests for specific ports to specific machines
behind the NAT. That is handy for hiding servers behind a NAT and for
redirecting traffic to different servers. But, it is not a solution to
your problem.

OTOH, all the machines behind the NAT can address the rest of the world.
The solution to your problem is to have the client contact the server,
not the other way around. And no, X can't get around NAT either. 

                Bob Pendleton

> 
> Any pointers would be appreciated.
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