When no command is specified, xon runs 'xterm -ls'. 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.
Runs xhost locally to add the remote host to the host access list in the X server.
This won't work unless xhost is given permission to modify the access list. Normally, xon disconnects the remote process from stdin, stdout and stderr to eliminate the daemon processes which usually connect them across the network. Specifying the -debug option leaves them connected so that error messages from the remote execution are sent back to the originating host. This option cause xon to specify an alternative user name. This will not work unless you have authorization to access the remote account, by placing an appropriate entry in the remote users .rhosts file.