Nmap is a utility for network exploration and security auditing.
It supports various types of host discovery (determine which hosts
are up), many port scanning techniques for different protocols,
version detection (determine service protocols and application
versions listening behind ports), and TCP/IP stack fingerprinting
(remote host OS or device identification).  Nmap also offers
flexible target and port specification, decoy/stealth scanning,
sunRPC scanning, and much more.

Also included is Ncat, the nc(1) work-a-like of the Nmap project.
Refer to the separate port security/zenmap for those parts of the
Nmap toolset which depend on python.  The translated manual pages
for Nmap are contained in security/nmap-i18n-man.

See the web page and the Phrack Magazine article (Volume 7, Issue 51
September 01, 1997, article 11 of 17) https://nmap.org/p51-11.html