Nmap

nmap is a commandline port scanner.

Tutorials

digitalocean	https://www.digitalocean.com/community/tutorials/how-to-use-nmap-to-scan-for-open-ports-on-your-vps
arch wiki	https://wiki.archlinux.org/index.php/Nmap

Usage

# don't use sudo. give your user permission to X
nmap -sP '192.168.1.*'  # scan all ips in addr range
nmap 192.168.1.0/24     # scan all ips in subnet
nmap 192.168.0.1-10     # portscan 192.168.0.{1..10}
nmap -p- 192.168.1.1    # scan all 65535 ports