How to open an X11 window on machines without ssh (also Xterminals) from hosts without ssh.
[ Using two hosts with ssh as forwarders ]

Last update: 4-Feb-1999

• From a machine without ssh (or from an X-Terminal) login on dxcalc or other machine with ssh (SSHhost);

• On the SSHhost issue the command:   ssh -R<6000 + DisplayNumber>:<YourXserverIPname>:6000   <RemoteSSHhost>

• On the RemoteSSHhost:   telnet   <RemoteNoSSHhost>

• On the RemoteNoSSHhost set display with server ip name as RemoteSSHhost and display number equal to DisplayNumber,
  i.e.:
  • On unix, with tcsh:

    > setenv DISPLAY <RemoteSSHhost>:<DisplayNumber>.0

  • On OpenVMS:

    $ set display/create/transport=tcpip/node=<RemoteSSHhost>/server=<DisplayNumber>

• Run your X11 application

Note:
You are free to choose your preferred DisplayNumber, but the number must refer to a free port on the RemoteSSHhost.
So we suggest to choose a number greater than 50 to avoid conflicts with local X11servers and other ssh X11 forwardings.
If, when you issue the ssh command, you receive the error "bind: Address already in use" simply choose another DisplayNumber.

Security Note:
The channel between your local Xserver and the local ssh host and the channel between the remote ssh host and the remote nossh host are NOT secure.

Example:

View a plot with paw running on a remote host without ssh on our local Xterminal.

• From the Xterminal (xterm01.lnf.infn.it) login on dxcalc;

• We choose 543 as DisplayNumber;
  dxcalc~> ssh -R6543:xterm01.lnf.infn.it:6000   sshhost.remote.edu

• sshhost~> telnet   vms01.remote.edu

• $ set display/create/transport=tcpip/node=sshhost.remote.edu/server=543

• $ paw