UDP packets to PC behind NAT

Janto Dreijer jantod at gmail.com
Fri Sep 15 16:58:42 CEST 2006

Grant Edwards wrote:
> On 2006-09-15, Janto Dreijer <jantod at gmail.com> wrote:
> > Would it be a reasonable solution to initiate a TCP connection
> > from the client to the server and somehow (?) let the server
> > figure out how the client is connecting? And then send UDP to
> > client over the same (IP, port)?
> I doubt that will work unless the firewall has been
> specifically designed to recognize that pattern of activity and
> allow the incoming UDP packets.  I don't think most firewall
> have default rules that allow UDP packets to tunnel back along
> a TCP connection.

Thanks for the info!

I think you may be right. I had to configure the local firewall to
allow all connections from the server. Which kinda defeats the purpose.
If you have control over the NAT why not just assign a dedicated port?

There might still be value in this approach, however. Even though I
have control over the NAT I have multiple clients that might need to
create these connections. I would need to map ports to be able to
handle simultaneous connections.

It's Friday afternoon over here, so I may be wrong...

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