The (almost) interesting history of Port Numbers

Port numbers are the numerical identifiers that allow computers to communicate over the internet. They are assigned to different applications and protocols, such as web browsing, email, file transfer, and so on.

But how did these port numbers come to be?

Who decided which port number belongs to which service?

And are there any interesting stories behind them?

In this article, we will explore the origins and evolution of port numbers, and reveal some of the hidden meanings and mysteries behind them.

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The Early Days of Port Numbers

The concept of port numbers dates back to the early days of the internet, when it was still called the ARPANET. The ARPANET was a network of computers that connected research institutions and universities in the United States, funded by the Department of Defense. It was the precursor of the modern internet, and the first network to use the TCP/IP protocol suite.

TCP/IP

The TCP/IP protocol suite is a set of rules and standards that govern how data is transmitted and received over the internet. It consists of four layers: the application layer, the transport layer, the internet layer, and the network access layer.

The port numbers are part of the transport layer, and they are used by two main protocols: TCP and UDP. TCP stands for Transmission Control Protocol, and it is a reliable and ordered way of sending and receiving data. TCP ensures that the packets are delivered without errors, and in the correct sequence. UDP stands for User Datagram Protocol, and it is a fast and simple way of sending and receiving data. UDP does not guarantee that the packets are delivered without errors, or in the correct order, but it is more efficient and suitable for real-time applications, such as video streaming or online gaming.

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Origin of port numbers

The port numbers range from 0 to 65535, and they are divided into three categories: well-known ports, registered ports, and dynamic ports.

The well-known ports are the ones from 0 to 1023, and they are reserved for the most common and standardized services and protocols, such as HTTP, FTP, SMTP, DNS, etc.

The registered ports are the ones from 1024 to 49151, and they are assigned to specific applications and protocols by the Internet Assigned Numbers Authority (IANA), which is the organization that oversees the allocation and management of port numbers, IP addresses, and other internet resources.

The dynamic ports are the ones from 49152 to 65535, and they are used for temporary and random purposes, such as client-server communication, peer-to-peer networking, or testing.

The first official list of port numbers was published in 1972, in RFC 322, which stands for Request for Comments. RFCs are the documents that describe the specifications and standards of the internet, and they are written and reviewed by experts and researchers from the internet community. The list contained 23 port numbers, assigned to the following services and protocols: