Newbie Needs Help
jim_hill_au-24 "at" yahoo.com.au
Thu Apr 13 01:40:01 2006
Jim Hill wrote:
> I use Ethereal to find out what's happening on the network.
> You may need a little time to learn to understand what it tells you, but
> that would be time well spent, very "empowering" ;)
> (Ethereal is free, from http://www.ethereal.com/download.html)
I should have added this:
go to ShieldsUp at https://www.grc.com/x/ne.dll?bh0bkyd2
on the next page, in the text box,
type the port you opened on your router.
at this point, start a capture in ethereal
then on the ShieldsUp page click
"User specified custom port probe"
when ShieldsUp has finished, stop the ethereal capture.
study the results.
if that port is being forwarded, you'll see it in ethereal.
[in ethereal you'd see something like this:
that port should first recv a SYN packet.
if nothing is listening on that port,
your machine sends back a RST packet.
if something is listening,
your machine sends back an ACK packet.
having got an answer, ShieldsUp sends a FIN packet.]
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