You can use SSH to easily make `x2x` link two displays together. SSH
provides the options to tunnel the X traffic from the host you are
connecting to the host you are connected from.

SSH propagates authentication token from the local host to the remote
host, and creates tunnel. For example, if you have access token to the
`$DISPLAY` on the local host, it will propagate
authentication token to the remote host, and forward local X connection to the display like `localhost:10` on the remote host.

SSH server and client have number of options to control the behavior
of the forwarding. The most frequently used options are listed in the
table below:

ssh server options (`/etc/ssh/sshd_config`)
||`X11Forwarding`||Specifies whether forwarding is allowed. May be 'yes' or 'no'.||
||`X11DisplayOffset`||Specifies first display number to be used. By default it is 	 '10', which means tunnel will be established from the `localhost:10` display. ||
||`X11UseLocalhost`||Specifies whether listening socket will be bound to the localhost only or to the all available network interfaces.||

ssh client options (`~/.ssh/config`, `/etc/ssh/ssh_config`)
||`ForwardX11` (command-line switches -X and -x)||Specifies whether to forward X connection to the remote host. Option -X enables forwarding, -x disables it.||

Full list of options is contained in man pages ssh(1), ssh_config(5)
and sshd_config(5).

Example configuration. host1 runs x2x and wants to control display on host2.

On the host1:
{{{
host1% echo $DISPLAY
:0.0
host1%
}}}

On the host2:
{{{
host2% ssh host1
Password:
host1% echo $DISPLAY
localhost:10
host1% x2x -from :0
}}}