What is a computer port and what are they used for?

What comes to mind when you hear the term “computer port”? USB ports? TCP/IP ports? It can get confusing. There are two types of ports: physical and virtual. A USB port is an example of a physical port, while a TCP/IP port is an example of a virtual port.

There are more virtual ports than physical ports, so let’s start with the physical ones. Both classes can be found on almost every electronic device. Phones, tablets, PCs and even electronic parts in cars and other machines can have both classes. For our purposes, we will refer to a computer in this article. Just know that it can be almost any device.

What is a gate?

So, what is a port? We can call these ports jacks or outlets, but the correct term is port. The basic function of these ports is to be able to connect one piece of hardware to another so that they can talk to each other. In technical terms, these are input/output (I/O or IO) ports. The number of ports a device can have is limited by the available physical space.

There are two groups of ports: serial and parallel. The grouping is based on how the port allows communication.

Only one bit can be transferred at a time on a serial port. Think of a train. Only one part of the train can be on a specific section of track at a time. The engine goes in front of the freight car, the freight car goes before the last car. If two are on the same section at the same time, it is a train wreck or a collision.

The same is true for data flowing through a serial port. Bit one and bit two can’t be on the same piece of cable at the same time or there’s a collision and things don’t work.

With a parallel port, many bits can be transferred at the same time. Think of a multi-lane highway. Every vehicle on the highway is a bit. On any specific section of the highway, there can be 5, 10, maybe 20 cars side by side at the same time. This ensures much faster communication. If it is not clear how, then it will be.

Let’s say we send a message to two people, such as “Hello”, by train and by truck. We send it to one by train and to another by truck. Every letter of hello is painted on the front of a truck and on the front of a train car.

The person waiting for the train, the serial method, sees the H on the locomotive, then the E on the next freight car, then the first L on the next car, then the second L on the next car and the O on the next car. last car.

The person waiting for the trucks on the 5-lane highway sees all the trucks arriving at once, side by side, with a nice expression HELLO.

Types of physical ports

DE-9 or RS-232 Port – General Purpose

You may still see these on some computers, but they are becoming less common outside of the industrial world. They were used with a mouse, keyboard and many other devices.

PS/2 – General Use

Most commonly seen on older computers, the Personal System/2 (PS/2) port was most commonly used for keyboards and mice. They are color coded: purple for the keyboard and green for the mouse.

PS/2 ports may still be seen on computers in high-security facilities. Having only PS/2 mice and keyboards eliminates the need for USB ports. Where there is a USB port, there is a chance that data will be stolen or malware injected.

USB Port General Information

There are 2 common major specifications for Universal Serial Bus (USB) ports seen today, the USB 2 and USB 3. These specifications refer to data transfer rates, not their physical form factor. There are several form factors that are discussed later in this section.

The USB 2.0 has a maximum data transfer rate of only 480 Mbps. There are several versions of USB 3, but they are all very similar visually apart from some markings that indicate the version. USB 3.0 is up to 5 Gbps and USB 3.1 is up to 10 Gbps and USB 3.2 is up to 20 Gbps. Yes, a USB 4 is also coming. A USB 3 device will work through the older USB 2 ports, but will only transfer data at the USB 2 speed.

Visually, the USB 2 Type A and Type B and their USB 3 counterparts can be easily distinguished by the color of the block in the connector. The faster USB 3.0 has a blue block where the slower USB 2.0 has a black block. The other types of USB connectors don’t have that kind of block. We go into their transfer speeds in their own sections.

If you want more information about the different types of USB cables, we also have an article about that.

USB Type A – General Purpose

You are certainly familiar with the USB Type A port. It is a port that can transfer data and provide power. It gives off electricity of about 5 volts. The current can vary from 100 mA to 500 mA or 0.5 Amps.

The type A descriptor refers to the form factor of the port. It is the most common rectangular one with half having a block of connectors and the other half being open to receive the mating connection. We also have an article on how to fix USB ports.

USB Type B – General Purpose

Usually seen on desktop printers, the USB Type B port has a square hole. They come in the USB 2 and USB 3 standards. The USB 2 one looks a bit like a shed end profile, while the USB 3 looks a bit like a stone fireplace.

USB Type C – General Purpose

The newer form factor of USB solves the annoyance of having to connect the cable properly. Anyway will work. It is a reversible connector. It also conducts current of about 5 Volts, but at a higher amperage than the USB Type A. It can be up to 5 Amps. This makes fast charging one of its features.

RJ-11 – Communication

We probably won’t find the RJ-11 on any device unless it’s being used for telephone or fax communications. Yes, it is a telephone connection. It can passively send an electrical signal, but some phone lines carry a current that can give you a serious shock if you’re not careful. Even if they are old-fashioned, respect them.

RJ-45 – Communication

Probably referred to as the network jack, the RJ-45 port is an 8-pin port for connecting devices to a network using an Ethernet cable. It looks like a telephone connection, but slightly wider.

3.5mm TRS connector – audio

These are most commonly used for audio devices. A green one is for connecting speakers or headphones. Pink is used for microphones. Blue is used for a direct connection from an audio device. It is also known as a line-in. There are other types, but they are not common on home appliances.

VGA/SVGA Port – Video

The Video Graphics Array (VGA) or Super Video Graphics Array (SVGA) port is used to connect monitors or projectors to a computer. VGA can provide resolution up to 640×480 and SVGA can go over 800×600.

Both types look identical. They look like the DE-9, but have 3 rows of 5 holes, where the DE-9 has a row of 5 and a row of 4 below.

DisplayPort – Video and Audio

If your computer has a slot that looks like a rectangle with one corner shaved off, it’s a DisplayPort. It is a 20-pin connector for connecting video devices. It’s also capable of transmitting audio over the cable, so if the device you’re connecting has speakers, it should also be recording your computer’s audio.

HDMI – Video and Audio

The High Definition Media Interface (HDMI) port is very popular. It is also a video port and can also carry the audio signal. These can be found on most PCs and many televisions.

Those are the different physical ports you are likely to encounter. If the port you are looking for is not found here, there are many port identification resources on the Internet.

Virtual ports

There are 65,535 virtual ports and they are all related to network communication. Each can have a different use depending on the type of data going through it. These ports are used for Transfer Control Protocol (TCP) or User Datagram Protocol (UDP) or both.

TCP is often lumped together with Internet Protocol (IP). You may have seen it as TCP/IP. TCP is used to open a connection between two devices so that data can be transferred. It does this by allowing one device to reach another and then an agreement is made between them to transfer data. This is known as a handshake connection. That could take a while.

UDP does not make a handshake connection. It just starts transmitting. It is faster, but because there are no agreements about how to do it, errors can occur.

In theory, any form of network communication can take place over any port. That would get really confusing with thousands of ports available. So we try to follow a standard to make life easier. The Internet Assigned Numbers Authority (IANA) does have a register of ports and what they are used for

When a communication packet enters a computer, it contains information about the port it wants to connect to. This way the computer can tell what to do with those packets. Therefore, you can view web pages, transfer files and print via the same network cable.

You may have seen port numbers used in IP addresses. It would be the number after the semicolon in an IP like

Following is a list of the ports you are most likely to encounter. We threw in the last one for all old school gamers Outside.

Port Description
20 File Transfer Protocol (FTP) data transfer takes place on this port
21 File Transfer Protocol (FTP) control messages sent on this
22 Secure Shell (SSH)
23 Telnet
25 Simple Mail Transfer Protocol (SMTP) for email
53 Domain Name System (DNS)
69 Trivial File Transfer Protocol (TFTP) simplified version of FTP
80 Hypertext Transfer Protocol (HTTP)
8080 Hypertext Transfer Protocol (HTTP) alternative
123 Network Time Protocol (NTP) for synchronizing computers
143 Internet Message Access Protocol (IMAP) for email
161 Simple Network Management Protocol (SNMP)
194 Internet Relay Chat (IRC)
443 Hypertext Transfer Protocol over TLS/SSL (HTTPS) Secure Connections
465 Authenticated SMTP over TLS/SSL (SMTPS)
587 Sending e-mail messages (SMTP)
515 Line Printer Daemon (LPD) connects printers to a computer
666 Doom, the first-person shooter (FPS) game

Ports, ports, ports…

Now you know what the most common physical and virtual ports are and what their tasks are. Bookmark this for a handy reference or print it out.

Have you come across any weird gates? Do you have questions about other ports or do you want more information? Let us know in the comments. We are here to help.

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