The preceding script first takes a list of network hosts, scan_hosts, from the command line. It then creates a schedule to launch the detect_inactive_hosts() function after a one-second delay. The target function takes the scan_hosts argument and calls Scapy library's sr() function.

This function schedules itself to rerun after every 10 seconds by calling the
schedule.enter() function once again. This way, we run this scanning task periodically.

The Scapy library's sr() scanning function takes an IP, protocol, and some scan-control information. In this case, the IP() method passes scan_hosts as the destination hosts to scan, and the protocol is specified as ICMP. This can also be TCP or UDP. We do not specify a retry and one-second timeout to run this script faster. However, you can experiment with the options that suit you.

The scanning sr()function returns the hosts that answer and those that don't as a tuple. We check the hosts that don't answer, build a list, and print that information.