Xon runs the specified command (default xterm -ls) on the remote machine using rsh, remsh, or rcmd. Xon passes the DISPLAY, XAUTHORITY and XUSERFILESEARCHPATH environment variables to the remote command.
When no command is specified, xon runs 'xterm -ls'. It additionally specifies the application name to be 'xterm- remote-host' and the window title to be '-fIremote-host '.
Xon can only work when the remote host will allow you to log in without a password, by having an entry in the .rhosts file permitting access.