Remote Controlling a KDE 4 Desktop

>> How can we set up a tunnel to allow just the support person to have to open a single
>> port on the local firewall, and allow this connection to be encrypted end-to-end?

> For remote computers, you'd need to forward the port on the firewall into the local
> computer, and set up some sort of dynamic DNS system (there are free ones) so you
> always know the address to connect to.

I understand how opening ports can be dangerous, hence why I asked about a tunnel with only opening the port on the support person's network, and using a tunnel to connect this way. I know it can be done (and I know how to do it), but my point is that your tutorial leaves a lot to be desired in making this actually usable for most situations.

For those who are interested in this approach, here is that tunnel over SSH. This command should be run on the sharing-desktop computer in a terminal (Konsole on KDE) after being adjusted for the correct IP addresses. Once this is run, set up the invitation (or use the always-available connection setup as explained in the video):

shellprompt:~$ ssh -R 5900:localhost:5900 USERNAME@remote.dynamicdns.com -p22
where:
USERNAME is a username on the support person's computer
remote.dynamicdns.com is the support person's IP Address or DynamicDNS domain name.
-p22 is the SSH port on that remote user's computer; 22 is standard SSH but it may be
different in some circumstances

The support person would then run the xtightvncviewer or whatever VNC viewer application to:
localhost::5900

After the connection is finished, the supported person then should run 'exit' in the terminal to close the tunnel to the supporter's computer. Note that during this time, the supported person has shell access to the supporter's computer, so do not use any account that may have root access. Also, having SSH port open to your box is a security risk and should be protected with good passwords, at a minimum.

Some VNC programs use port 5500 and others use 5900, which can make a failed connection confusing for a new user and should be clarified (which you just did, so thank you).