I am setting up secure VNC access to three remote computers behind a firewall using SSH. For example the private IPs of the three machines are:
I have setup the following NAT through the firewall:
so essentially calls to the public IP on port 22 are forwarded to the first machine, which also has cygwin OpenSSH server listening. I then use an SSH client to connect to that machine, no problems and works as expected. I then setup the following SSH tunnels in the SSH client:
Connecting UltraVNC Viewer to localhost:15902 and localhost localhost:15903 work exactly as expected and I can access these two via the SSH tunnels. The problem however is attempting to connect to localhost:15901 which does not work at all. The first error was "Loopback connections are disabled", so I enabled loopback connections in the configuration. Now the error is "Connection Failed, Error reading Protocol Version". All three are setup exactly the same way and testing among the three on the local network works fine. I am guessing there is a problem with the loopback because this is the system with the SSH NAT forward. Interestingly if I setup the following tunnels for Microsoft Remote Desktop:
then all three remote desktop sessions work perfectly, but I really wish to use VNC. Am I missing something? NAT forward of port 5900 is not possible unfortunately.
This is being setup for our engineering staff so I am trying to keep things very simple, and I have done this many times for both windows and linux hosts using realvnc with no issues, but UltraVNC has the built in file transfer which I want the eng staff to use without having to launch a separate SCP client.