What is Nmap Port Scanner?
Nmap Port Scanner (“Network Mapper”) is a free and open source (license) utility for network discovery and security auditing. Many systems and network administrators also find it useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.
Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics.
It was designed to rapidly scan large networks, but works fine against single hosts. Nmap runs on all major computer operating systems, and official binary packages are available for Linux, Windows, and Mac OS X. In addition to the classic command-line Nmap executable, the Nmap suite includes an advanced GUI and results viewer (Zenmap), a flexible data transfer, redirection, and debugging tool (Ncat), a utility for comparing scan results (Ndiff), and a packet generation and response analysis tool (Nping).
How to install Nmap Port Scanner?
In ubuntu linux you can install it in two ways
# Fist update
sudo apt-get update
# Now install via apt
sudo apt-get install nmap
# Or install via snap
sudo snap install nmap
Code language: PHP (php)
Basic usage and examples:
Default nmap output:
# Default simple output
sudo nmap website.info
Code language: CSS (css)

How to scan a domain for open ports , operating system, uptime and more?
# Deep Scan
sudo nmap -O -v website.info
Code language: CSS (css)

You can scan a whole subnet or IP range with Nmap by providing * wildcard with it
# Scan Whole network
sudo nmap 192.168.0.*
# Scan a specific range
sudo nmap 192.168.0.101-110
Code language: CSS (css)

sudo nmap -iL nmaptest.txt