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no not a airport device. All hard wired network. needing to find the list of all computers/devices on the network
 
You can install nmap, then run something like "nmap 192.168.1.0/24" to scan the entire IP range.

You can also run "arp -a" to see a list of current ARP entries, though this may not show the entire network.
 
If it's your network, why not log into the router and see the DHCP table?

The tools mentioned above will work too. Can also try pinging the broadcast address to see if anything else replies. Simple, but not foolproof. In a command window: ping 192.168.1.255... or whatever network/subnet combo you use.
 
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