The second case opens an icoming tunnel... I 'try to explain:

You have e http server listening on your machine at port 80 but just
on localhost (127.0.0.1)

you make a ssh -r 80:remotehost:5900 remotehost

then, on the remote host, if you telnet localhost 5900 you got your
http server ...

Hope it was clear enogh

cheers

On 5/9/08, arguellodw <arguellodw (at) yahoo (dot) com [email concealed]> wrote:
>
> Hello all,
> I'm having a difficult time understanding the difference between these two
> local tunnels. Here is how I see them:
>
> ========================================================================
===
> 1) mymachine: $ ssh 5900:localhost:5900 remotehost
> ==> I'm sitting in front of a computer called mymachine, and ssh opens port
> 5900 for listening on mymachine and ties the other end of it to port 22 of a
> computer called remotehost. The ssh server on remote host then forwards
> anything it receives at this port from socket:(mymachine's IP, 5900) to
> socket:(remotehost IP, 5900). A schematic might go like this --
>
> (mymachine's IP, 5900) --> (mymachine's IP, ssh-chosen port) --network-->
> (remotehost IP, 22) --> (remotehost IP, 5900)
>
> 2) mymachine: $ ssh 5900:remotehost:5900 remotehost
> ==> I'm in front of a computer called mymachine, and ssh opens port 5900 for
> listening on mymachine and ties it to port 5900 on a computer called
> remotehost. A schematic might look like this:
>
> (mymachine's IP, 5900) --network--> (remotehost IP, 22) --> (remotehost IP,
> 5900)
> ========================================================================
===
>
> I'm pretty sure I have the right idea in the first instance, but I don't
> think I'm right on the second one. According to O'Reilly, the two command
> lines accomplish the same thing as far as forwarding the port, but there is
> a subtle difference in that the source sockets of the connection are
> different from the POV of the receiving end (remotehost IP, 22).
>
> Can somebody put me on the right track to understanding exactly what these
> commands accomplish?
> Thanks,
> Dan Arguello
> --
> View this message in context: http://www.nabble.com/What-is-difference-between-%275900%3Alocalhost%3A5
900-remotehost%27-and-%275900%3Aremotehost%3A5900-remotehost%27--tp17138
548p17138548.html
> Sent from the SSH (Secure Shell) mailing list archive at Nabble.com.
>
>

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