Port forwarding that automatically disconnects

If you want to tunnel a long-lived connection over SSH such that the tunnel goes away when the application disconnects, try something like the following example:

ssh -f -q -L 5900:localhost:5900 user@remotehost.com sleep 60

By executing "sleep 60" remotely, the tunnel stays alive for at least 60 seconds, and assuming your application has connected by then, the tunnel will continue to stay alive until the application disconnects.

The options given above are perfect for executing this command from a script; it is quiet (-q) and goes to background after prompting for a password (-f). This particular example forwards the VNC protocol so that when your VNC client connects to localhost, it connects securely to remotehost.com over the tunnel.