Finding all IPs listening on a particular port using nmap:

nmap -p 80 --open -sV 192.168.1.0/24

Refs: * http://thoughtsbyclayg.blogspot.co.uk/2008/06/use-nmap-to-scan-for-ssh-servers-on.html * https://www.digitalocean.com/community/tutorials/how-to-use-nmap-to-scan-for-open-ports-on-your-vps