Nmap (Network Mapper) is a free and open-source network scanner created by Gordon Lyon (also known by his pseudonym Fyodor Vaskovich). Nmap is used to discover hosts and services on a computer network by sending packets and analyzing the responses.
Nmap provides a number of features for probing computer networks, including host discovery and service and operating system detection. These features are extensible by scripts that provide more advanced service detection, vulnerability detection, and other features. Nmap can adapt to network conditions including latency and congestion during a scan.
Nmap started as a Linux utility and was ported to other systems including Windows, macOS, and BSD. Linux is the most popular platform, followed by Windows.
Scan a single port
nmap -p 22 192.168.1.1
Scan a range of ports
nmap -p 1-100 192.168.1.1
Scan 100 most common ports (Fast)
nmap -F 192.168.1.1
Scan all 65535 ports
nmap -p- 192.168.1.1
Scan a port for all ciphers used
nmap --script ssl-enum-ciphers domain.com -p 443