Hacker News Reader

You can use nmap for checking presence of the host, open ports and the OS machine running.

This tool has great documentation, see https://nmap.org/book/intro.html for more details

nmap in movies:

Some times you can’t make out the text in films, but that is what Enhance is for.

And on the reverse side, OS fingerprinting by the packets you receive: https://lcamtuf.coredump.cx/p0f3/