complicated router question....

[kyle]

Thank you Brian, your last message helped to clear up
alot of my conceptual misunderstandings of what was
going on.
-Kyle

--- Brian Cluff <brian@snaptek.com> wrote:
> > But this is what i dont get... How come i can run
> a
> > file sharing program like bearshare or icq and ppl
> can
> > send me messages or download songs from me?
> >
> > So somehow those applications are opening ports
> for
> > traffic to come in... but i dont know why or how.
> Even
> > where i work i cannot run a web server behind the
> > firewall but i can run bearshare and i punches
> right
> > thru the firewall to open up a port and where i
> work
> > we have one anal firewall.
> 
> Actually when you run those you aren't opening
> anything up to the world.
> What happens is that you are connected to a server
> somewhere and someone
> wants to download something from your machine, it
> will first try and get it
> directly, but will realize that you are behind a
> firewall, so it will send a
> message back though the server system that its
> trying to get ahold of file
> such and such and the server will tell your machine
> that you need to open a
> connection to someone else and send them a file.
> If both people are on fake networks then there is no
> way to directly
> transfer the file, unless they completely bounce it
> though a server
> somewhere.
> 
> With icq, the person on the other end probably got a
> message along the lines
> of "Cannot establish a direct connection, send to
> server instead."  ICQ
> works the same way,  all incoming messages get
> routed though the server that
> you are already connected to.
> 
> You might notice that some things just plain dont
> work, depending on the
> quality of the masquarading in the dsl model.  You
> might not be able to
> receive incoming files or chats through ICQ.
> 
> Brian Cluff
> 
> 
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