Although port scanning is obviously very important for security professionals—after all, without understanding what network ports are open, it would be impossible to assess the security of a system—Nmap is also very valuable for other types of information technology professionals.

System administrators use Nmap to determine which of their systems are online, so they can understand if there are problems or inconsistencies on their network. Similarly, using OS detection and service detection, these administrators are able to easily verify that all systems are running the same (hopefully current) versions of operating systems and network-enabled software.

Because of its ability to change timing, as well as set specific flags on different packets (for example, the Xmas Tree scan), developers can turn to Nmap for help in testing embedded network stacks, in order to verify that the aggressive network traffic won't have unintended outcomes that may crash a system.

Lastly—and perhaps most importantly—students of network and computer engineering are major users of Nmap. Because it is a free and open source software, there is no barrier to get the software and run it immediately. Even amateur users scanning their own small home networks can learn an immense amount about how their computers and networks work and are configured by seeing what services are online. Although there are Windows and OS X ports, Nmap is also a great introduction to running straightforward (but advanced) tools on the Linux command line.