rwall —
send a message to users logged on a host
The rwall command sends a message to the users logged
  into the specified host. The message to be sent can be typed in and terminated
  with EOF or it can be in a file.
  - rwall: RPC: Program not registered
- The rpc.rwalld(8) daemon
      has not been started on the remote host.
- rwall: RPC: Timed out
- A communication error occurred. Either the network is excessively
      congested, or the
      rpc.rwalld(8) daemon has
      terminated on the remote host.
- rwall: RPC: Port mapper failure - RPC: Timed out
- The remote host is not running the portmapper (see
      rpcbind(8)), and cannot
      accommodate any RPC-based services. The host may be down.
Therwall command appeared in SunOS.