Network Utility is an application included with Mac OS X

Mac OS X

Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...

 that provides a variety of computer network information. It is located at /Applications/Utilities/Network Utility.app.

Services

• Network interface
  Network interface
  Network interface may refer to:* Network interface controller, the device a computer uses to connect to a computer network* Network interface device, a demarcation point for a telephone network...
  
  s
• Netstat
  Netstat
  netstat is a command-line tool that displays network connections , routing tables, and a number of network interface statistics...
  
  
• AppleTalk
  AppleTalk
  AppleTalk is a proprietary suite of protocols developed by Apple Inc. for networking computers. It was included in the original Macintosh released in 1984, but is now unsupported as of the release of Mac OS X v10.6 in 2009 in favor of TCP/IP networking...
  
  
• ping
  Ping
  Ping is a computer network administration utility used to test the reachability of a host on an Internet Protocol network and to measure the round-trip time for messages sent from the originating host to a destination computer...
  
  
• Lookup
  Lookup
  In computing, lookup usually refers to searching a data structure for an item that satisfies some specified property. For example, variable lookup performed by a language interpreter, virtual machine or other similar engine usually consists of performing certain...
  
  
• Traceroute
  Traceroute
  traceroute is a computer network diagnostic tool for displaying the route and measuring transit delays of packets across an Internet Protocol network. Traceroute is available on most operating systems....
  
  
• Whois
  WHOIS
  WHOIS is a query and response protocol that is widely used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name, an IP address block, or an autonomous system, but is also used for a wider range of other information. The protocol stores...
  
  
• Finger
  Finger protocol
  In computer networking, the Name/Finger protocol and the Finger user information protocol are simple network protocols for the exchange of human-oriented status and user information.-Name/Finger protocol:...
  
  
• Port scan

Port scan

Network Utility uses the tools supplied in the unix

Unix

Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

 directories for most of its functions, however for the port scan it uses a unix executable in its resources folder, stroke, found at /Applications/Utilities/Network Utility.app/Contents/Resources/stroke.