[lug] Listening services and NAT on both ends

[Anthony Foiani]

Chris Riddoch <riddochc at gmail.com> writes:

> But suppose both users are on laptops at coffee shops, where neither
> has access to set up port forwarding rules, and neither has a hosted
> server someplace else they could both connect through - they're
> nontechnical users, with no need for such a server in general.

I've never investigated whether it is workable or not, but I wonder if
uPNP port forwarding works even at coffee shops?

Here in Albuquerque, we have a chain of eateries called "Flying Star".
They provide free Wi-Fi through Sputnik (which itself seems to be
built on the OpenWRT-style routers).  It looks like they've turned on
uPNP, although only fairly recently (last year):

   http://www.sputnik.com/support/changelog/files/sputnikagentfirmware33762.php

There's a generic uPNP framework available:

   http://pupnp.sourceforge.net/

In an ideal world, Alice and Bob can communicate through NAT routers
on both ends of a communication by doing something like so:

1. Alice tells Bob (through some out-of-band method) that she's
   willing to act as a server.  She uses uPNP to map her local server
   port to an external port on public IP of the NATing router.

2. Bob configures his client to talk to Alice's server by using the
   external port and IP he gets from Alice.

Not sure how easy that is to do in reality, though.

Happy Hacking,
t.