[Techtalk] Problem with tunneling SSH

[David Sumbler]

Some of you may remember that I have an elderly friend, Margaret, who
has a computer and likes to converse via Instant Messaging with me.
 Unfortunately she is now very confused, and often I don't hear from
her for days.  However, I am pleased to say that occasionally she still
logs in.

Recently we had quite a detailed chat about her computer having "gone
wrong".  It hadn't, of course, but she had inadvertently changed some
settings.  Using TeamViewer I was able to connect to her desktop and
sort things out.

It would be useful for me sometimes to be able to SSH to a terminal,
and this is something I used to do quite often.  But I have tried to do
it lately (at times when I know her computer is running because I am in
the middle of a conversation with her).  But I can't make a straight
connection.

I use a no-ip.com host-name, or by logging in to the no-ip website I
can see the current IP address of the care home where Margaret now
lives.  I have also set the computer up to allow SSH connections on an
arbitrary port number.  This used to work fine, but not now.

If I try a straight connection it doesn't work, e.g.

ssh margaret at heraddress.no-ip.org -p 12345

So I tried a tunnelled connection like this:

ssh -L 8888:192.168.1.140:22 margaret at heraddress.no-ip.org

or

ssh -L 8888:192.168.1.140:12345 margaret at heraddress.no-ip.org

I got her IP address on the local network by using ifconfig -a when I
was logged into her desktop.

I also tried substituting the actual IPv4 address as reported by no-
ip.com for heraddress.no-ip.org, but this didn't help.

One strange thing is that although no-ip.com reports a regular IPv4
address for the network Margaret's computer is attached to (and it is
being updated by Margaret's computer), if I visit whatsmyip.org and
similar sites from Margaret's desktop they report an IPv6 number.
 Entering this number into an online IPv6 to IPv4 converter tells me
that this address is not IPv4 compatible.

Any suggestions, anyone?

David