Scanning my home network (nmap)

Scanning my home network for all devices that are listening
on port 80 (http):
nmap -p80 -oG - | grep 80/open
Sometimes this doesn't work (because nmap tries to be smart and only scan hosts that are available). In order to make nmap scanning without intelligence, use the e-Pn (no ping) option. This scans all ports of host
nmap -Pn -p0-65535