Mac OS X: What is a Port?

A port is a location use for passing data in and out of your computer.

There are three categories of ports related to Mac OS X and the computers that use them:

  1. Device ports (hardware)
  2. Network ports (hardware)
  3. IP ports
     

Device ports

These hardware ports allow you to connect to video, storage, and input-output devices, such as displays, hard drives, mice, keyboards, and printers. Some common device ports include:

  • Universal Serial Bus (USB)
  • FireWire
  • Mini-VGA video
  • DVI
  • HDMI
  • Thunderbolt
  • Sound input
  • Sound output (or headphone)

Note: These ports are sometimes referred to as "jacks" or "sockets". These terms often appear in association with more traditional terms for the type of wire or cable connector that is being used, such as a "headphone jack".
 

Network ports

Ethernet and modem ports are examples of ports used to connect to a network. An AirPort card is also a network port. The Network preferences pane in System Preferences is used to configure network ports.

Note: These are sometimes referred to as "network interfaces," such as in the Network Utility application.
 

IP ports

Servers often deliver more than one type of service, so using the Internet address (URL) of a server is not enough. You must also tell the server what service is being requested. These requests are made by "port" number. For example, web service (HTTP) is commonly delivered on port 80. Web browsers are programmed to assume that you want port 80 when you type a URL, such as "www.apple.com". That is why you do not need to be aware of which port you are using for most web browsing. IP stands for "Internet protocol," which can be subdivided into port types such as TCP and UDP.

To learn more about these ports, see Well known TCP and UDP ports used by Apple software products.

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