[plug] Skype

[Alan Graham]

I use skype, and I didn't make any changes to my firewall setup.  It's a
very interesting question...

I'm running bastille on debian as a firewall, and have skype running on
my Mandrake desktop, a win2k machine for the kids, and on my wife's
powerbook (Mac os x).  Skype, as promised, "just works".  

The technical faq says that all skype needs for incoming calls is port
80.  However, on my firewall, port 80 is dropped.  The faq also says you
can open a TCP or UDP port defined in the Skype options (chosen randomly
on installation, but modifiable), which port you choose to use is up to
you.  This just confuses things more, as how can an incoming port be
random?  Yet, I receive calls quite happily.

The technical faq also says that Skype uses p2p technology (now there's
a nice bit of technobabble).  I assume that this means that there's a
presence packet sent to other skype users.  Presumably this means that
an incoming call is routed through Skype clients to find you, and is
piggybacked onto a reply to a presence packet that you initiated?  The
presence packets would therefore be TCP, switching to UDP for the
coversation?  Maybe?  As it's a closed source, proprietary protocol,
we'll have to wait for someone to reverse engineer it...  :)

Alan


On Fri, 2004-11-12 at 20:43, garry wrote:
> Anyone here using Skype?
> 
> Do you have to open any INcoming ports on the firewall? The 
> http://www.skype.com/help/guides/firewall.html says to open OUTgoing 
> ports, but says nothing about incoming...
> 
> To receive a call, it'd be logical that at least one incoming port would 
> need to be open..
> 
> (Having said that, I'm hoping I don't have to - it'd save me working out 
> the syntax for iptables to forward it!)
> 
> Thanks in advance..
> 
> Garry
> _______________________________________________
> PLUG discussion list: plug at plug.linux.org.au
> http://mail.plug.linux.org.au/cgi-bin/mailman/listinfo/plug
> Committee e-mail: committee at plug.linux.org.au