[Gllug] Port filtering question

[Walter Stanish]

> I have been struggling with this for a few days now. I am trying to set up
> an icecast server on my desktop machine. Everything seems to be working
> fine, except that nobody can connect to the port.
>
> ....
>
> I am not running any kind of firewall or packet filtering firewall
> software on the PC as far as I can tell, as I generally use the router as
> the firewall. So is this a bug in the router, an ISP issue or is there
> something on the desktop machine doing this ?

One way to find out which part of your network infrastructure filters a port
is to run a traceroute with that port selected.  Whilst traceroute is a cool
hack, and old versions tended not to use TCP, modern implementations
such as that in recent versions of nmap will allow you to specify UDP or
TCP ports, along with a host of other options.

For a simple example, you could use:
 nmap --traceroute -PT -p80 your.target.host.com

I seem to remember that icecast doesn't normally run on port 80 by
default, a quick google suggests '8000'.

- Walter
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