What is a Port?

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Ports are virtual pathways on which Internet data flows. You probably know that data on the Internet is sent to and from IP addresses. If you are not sure about what an IP address is then check out our What is an IP Address guide. What you might not have known is that all data sent to an IP address is sent on specific ports.

If we think of an IP address as a telephone number, (an identifying number that allows communication between two locations), then we can think of ports as telephone number extensions. Suppose you wanted to make a telephone call to a major corporation; Ford for example. If Ford only had one simple telephone line it would take a very long time for your call to finally get through. However, by using telephone number extensions, Ford can channel incoming calls to the proper locations and as a result handle many calls on one line as opposed to just one call.

Ports are like telephone number extensions as they allow multiple pieces of data to flow back and forth on a single IP address. In fact, port numbers are appended to the end of IP addresses just as extensions are appended to telephone numbers.

In other words, ports are numerical identifiers that make it possible for you to check your email and browse the web at the same time. Technically speaking, this is possible because browsing the web traffic generally uses port 80, and getting your email generally uses port 110.

Technical Facts about Ports

  • Ports are a 16-bit number can range from 1-65535
  • TCP and UDP packets specify the port on which they are to be sent in their packet header
  • The ports that a given application uses are generally set by the programmers of that application

Ports in Relation to Port Forwarding

Now that you know what ports are, how do you use that knowledge to your advantage? One way is to learn how to forward ports. Port forwarding is the simple action of telling your router to pass the information that it receives on a given port directly to a specific device on your network. This can decrease the delay in information reception resulting in increased performance of your applications. For more information on port forwarding, please see our What is Port Forwarding page.

Ports in Relation to IP Addresses

Remember at the top of this page when it was mentioned that ports are appended to the end of IP addresses just as extensions are appended to telephone numbers? There is a specific syntax for appending port numbers to IP addresses and it is as follows:

  • (IP Address):(Port Number) or..
  • 27.1.1.1:80

Notice the colon acting as a separator between the IP address and the Port Number. Port Numbers are appended to the end of all IP addresses whenever data is sent.

Why don't I see a port number appended to the end of web addresses?

There are a few commonly used port numbers. Web traffic uses port 80 and is in fact so common that port 80 is assumed to be appended to the end of a web address by your internet browser and thus can be left off. You can test this by typing google.com:80 into your browser's address bar. When you press enter, you should go straight to google. Now, try typing google.com:6060 into your browser's address bar. When you press enter, you will not be connected to google. For more information on common ports and which applications use them please see our Port List page.

In order to fully understand what ports are and how they work, you must first have a solid understanding of IP addresses. For more information on IP addresses click here. If you have questions, please use our forum as an information source. There are many knowledgeable people there who will be happy to answer any questions that you might have.

Jason Bauer

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Jason Bauer is an owner and programmer for Portforward.com. He's available on Google+, twitter and facebook, and you can find more of his articles in the Guides section.