What are Port Numbers?

When a computer, phone or other device connects to the Internet it can run several programs.

Each program shares the same Internet connection and they can send and receive different types of data, such as web pages, emails, or instant messages.

So, how does a device know which application it should give each type of data? Because it device uses port numbers to help direct the data it receives to the correct application.

An IP address will ensure the data arrives at your device. Once there, the port number ensures that it gets to the right application.

If you compare IP addresses to a company's phone number; the port number is like an extension you dial (or option you press) that gets you through to the right person or department.

Diagram showing how one IP address splits off into separate port numbers for different applications

Port numbers are divided into three ranges:

  • Well-known ports
  • Registered ports
  • Ephemeral ports

1. Well-known ports or system ports are from 0 - 1023. The operating system uses them for processes that provide widely used types of network services.

HTTPWeb traffic80
SMTPSending email25
IMAP4Fetching email143
IMAPSFetching emial over TLS993
POP3Fetching email110
FTPFile server21
FTPSFile server of TLS /SSL990
DNSDomain name system53

2. Registered ports have numbers from 1024 - 49151. They are for specific services that companies have registered with IANA (The Internet Assigned Numbers Authority oversees Internet Protocol-related symbols and numbers such as IP address allocation, media types, and port numbers.)

XBOX live3074
Playstation network3479/80
Apple remote desktop3283
MS Terminal Server RDP3389

3. Ephemeral ports have numbers from 49152-65535, they are used for temporary purposes (such as tabs in a browser) also known as dynamic or private ports. They are used for private, customized services, or for termportary purposes