Clients to query the rwho server

 The rwho command produces output similar to who, but for all machines on
 the local network. If no report has been received from a machine for 11
 minutes then rwho assumes the machine is down, and does not report users
 last known to be logged into that machine.
 .
 The ruptime command gives a status line like uptime for each machine on the
 local network; these are formed from packets broadcast by each host on the
 network once a minute.