[Techtalk] {SPAM 05.1} Re: Problem with tunneling SSH

[David Sumbler]

On Thu, 2018-07-12 at 10:18 +0100, James Sutherland wrote:
> On 12/07/2018 10:02, David Sumbler wrote:
> > 
> > Sorry it has taken me a while to respond to your messages; I was
> > away
> > cycling in Scotland until yesterday.
> You timed that well - it's pouring with rain here now, after a long
> heatwave!
> 
> The problem here is she's behind 'NAT', sharing a single IP address
> with
> everyone on that network - outgoing connections will work fine, but
> nothing can come back in, since her computer isn't set up as a server
> on
> their router. When you try connecting to the public IP address, the
> router doesn't know which machine to forward the request to: like
> trying
> to return a call to a company switchboard, instead of a direct dial
> number.
> 
> TeamViewer sets up a tunnel of its own behind the scenes, connecting
> to
> their own servers to get around this.
> 
> If you have a server of your own, you can set up the same sort of
> thing
> with ssh - run this command on *her* machine, to connect to yours
> (138.47.99.99 in this example):
> 
> ssh -R 19999:localhost:22 sourceuser at 138.47.99.99
> 
> That sets up port 19999 on your machine, tunnelled back to SSH on
> hers,
> so you can then SSH to her from that machine any time with:
> 
> ssh her at localhost -p 19999
> 
> 
> Initially it will ask for your password on her machine; to fix that,
> on
> that machine (presumably via TeamViewer):
> ssh-keygen
> ssh-copy-id david at 138.47.99.99
> 
> (This creates an encryption key on her machine, then copies that to
> the
> account david at 138.47.99.99 to be used for logging in instead of a
> password in future: once that's done, the 'ssh -R' command above
> should
> run without any password needed.)
> 
> 
> James.

Thanks for all that.  I'll try it the next time I can access her
machine.  There is no perceptible pattern to when she remembers about
the computer and decides to switch it on.

My brother and I always seem to be lucky with the weather for our
cycling trips.  We actually finished in bright sunshine on
Mondayafternoon, and left Fort William (by car) on Tuesday morning.  By
the time we got to his house in Nottinghamshire, I gather it was
already chucking it down in NW Scotland.

David