Nuclear Structure at the HISKP Bonn: VNC

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SSH/PuTTY & VNC

To work from outside the institute - e.g. during a conference - on one of the institute computers, VNC could be used together with ssh/PuTTY.

PuTTY is a freely available ssh-client for Microsoft operating systems.

VNC is a system that allows working remotely on a computer. Under Linux this also works with virtual screens, that are screens existing only in memory. A nice feature of the system is that closed connections do not necessarily mean closed windows and terminated applications. VNC is freely available under GPL. VNC needs a server on the institute computer and a viewer on the remote computer.

• For Windows the VNC Free Edition Viewer for Windows in Executable form is sufficient, as offered on RealVNC as Free Edition.
• For Linux, most distributions include a package named like vncviewer.

Using VNC

First a VNC server has to be startet. As mainly Linux computers are used in our group, only the procedure to get a virtual screen will be explained. To get one, teh program vnc4server has to be started as vnc4server :n -localhost where n is a small number, e.g. 2, denoting the number of the display. Starting for the first time, a password has to be chosen.

To test if the server works, one can run xvnc4viewer :n on the same conmputer to see the new screen.

For remote use, a connection has to be established first.

• Using ssh one has to call ssh -L 590n:localhost:590n my.computer.
• If putty is used, a tunnel has to be set up in the settings dialog under Connection/SSH/Tunnels with options Source port=590n, Destination=localhost:590n and Local.

As most institute computers are not accessible from outside, two tunnels have to be built: one from the remote computer to an accessible institute computer, the second from there to the computer with the virtual screen.

Finally, the screen can be used by calling vnc4viewer :n under Linux and by starting the VNC Viewer and typing :n in the connection dialog under Windows.

The server need not be stopped but can be left running and also can be used from inside the institute. If the server should be terminated, the command is vnc4server :n -kill.

Brief version

• on the institute computer I, before departure:
  • vnc4server :n -localhost
  • test with xvnc4viewer :n
• on the Laptop L and the access computer A:
  • tunnel depending on L's operating system
    • Linux: ssh -L 590n:localhost:590n A
    • Windows: PuTTY, Connection/SSH/Tunnels, Options Source port=590n, Destination=localhost:590n und Local.
    From A continue with ssh -L 590n:localhost:590n I
  • viewer depending on L's operating system
    • Linux: vnc4viewer :n
    • Windows: VNCViewer, :n.