Determine users of nearby machine from CLI

Ok, so at my house I have three computers, and I frequently enjoy using ssh and scp to run commands that allow me to do wonderful things. Primarily transferring downloaded files, and running media remotely (music, video etc.). Usually I use the arp -a command to determine which other computers are on my network, but this only shows the local IP's. I often forget the **users** that exist on my other machines, and I would like to be able to: **have a command that shows me the users of a remote computer either by network or IP address**