The rpc.rusersd utility is a server which returns information about users currently logged in to the system.
The currently logged in users are queried using the rusers(1) command. The rpc.rusersd daemon is normally invoked by inetd(8).
The rpc.rusersd utility uses an RPC protocol defined in /usr/include/rpcsvc/rnusers.x.
rusers(1), w(1), who(1), inetd(8)