Detecting all hosts in a network which are online

An ARP scan can be used to find all devices and hosts in a network which are currently online.

nmap -PR -T4 -n -sP 192.168.0.0/24

The meaning of the parameters are:
-PR do an ARP ping to find hosts
-T4 assume to have a reasonable fast network
-n no reverse DNS resolution to speed up the scan
-sP ping scan, determine if the host is online