When you hear the term computer port, what do you think of? USB ports? TCP / IP ports? This can be confusing. There are two classes of ports – physical and virtual. The USB port is an example of a physical port and the TCP / IP port is an example of a virtual port.
There are more virtual ports than there are physical ports, so we’ll start with the physical ones. Both classes can be found on almost any electronic device. Phones, tablets, PCs, even electronic parts in cars and other cars can be of both classes. For our purposes in this article, we will refer to a computer. Just know that it can be almost any device.
What is the port?
So what is a port? We may call these ports sockets or receptacles, but the correct term is port. The main function of these ports is to allow one device to connect to another so that they can communicate with each other. From a technical point of view, these are input / output ports (I / O or IO). 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.
A serial port can only transmit one bit at a time. Imagine a train. Only one part of the train can be on a certain section of the track at a time. The engine goes ahead of the freight car, the freight car goes in front of the last car. If any two of them are on the same section of the track at the same time, it means a train wreck or collision.
The same goes for data passing through the serial port. The first and second bits cannot be simultaneously connected to the same section of the cable, otherwise there will be a conflict and something does not work.
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The parallel port can be capable of transmitting many bits at the same time. Imagine a multi-lane highway. Every car on the track is a little. On any particular section of the highway, there can be 5, 10, maybe 20 cars at the same time, next to each other. This greatly speeds up communication. If it is not clear how, then it will be.
Let’s say we send a message to two people, for example “Hello”, by train and truck. We send it to one person by train and to another by truck. Each greeting letter is painted on the front of the truck and railroad car.
A person waiting for a train (sequential method) will see an H on the engine, then an E on the next freight car, then the first L on the next car, then a second L on the next car, and an O on the final car.
A person waiting for trucks on a 5-lane highway will see all trucks arrive at the same time, side by side, pronouncing HELLO beautifully.
DE-9 or RS-232 port – general use
Physical Port Types
DE-9 or RS-232 – General Use
You can still see this on some computers, but outside the industrial world, they are becoming less and less common. Previously, they were used with mice, keyboards, and many other devices.
PS / 2 – General Use
Mostly 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 can still be seen on computers in high security environments. Having only PS / 2 mice and keyboards eliminates the need for USB ports. With a USB port, there is a risk of data theft or malware injection.
General USB port information
There are two general core specifications for Universal Serial Bus (USB) ports that can be seen today: USB 2 and USB 3. These specifications refer to data transfer rates, not physical form factor. There are several different form factors that will be discussed later in this section.
USB 2.0 has a maximum data transfer rate of just 480 Mbps. There are different versions of USB 3, but they are all visually very similar, with the exception of some markings indicating the version. USB 3.0 up to 5 Gb / s, USB 3.1 up to 10 Gb / s, and USB 3.2 up to 20 Gb / s. Yes, USB 4 is coming soon. The USB 3 device will work over the old USB 2 ports, but will only transfer data at USB 2.
Visually, USB 2 Type A and Type B and their USB 3 counterparts can be easily distinguished by the color of the block inside the connector. The faster USB 3.0 has a blue block, while the slower USB 2.0 has a black block. Other types of USB connectors do not have this blockage. We’ll cover their rates in separate sections.
If you need more information on the different types of USB cables, we have a related article.
USB Type A – General Use
You know for sure about the USB Type A port. It is a port capable of transmitting data and transferring power. It outputs electricity at about 5 volts. The current strength can vary from 100 mA to 500 mA or 0.5 A.
Type A descriptor refers to the port form factor. It is the most common rectangular one, half of which has a connector block and the other half is open to receive the corresponding connection. We also have an article on repairing USB ports.
USB Type B – General Use
The USB Type B port, which is most commonly found in desktop printers, has a square hole. They come in the USB 2 and USB 3 standards. USB 2 is a bit like a barn end profile, and USB 3 is a bit like a stone fireplace.
USB Type C – general use
The new USB form factor solves the problem of properly connecting the cable. Will work anyway. This is a reversible connector. It also conducts about 5 volts of power, but with more amperage than USB Type A. It can go up to 5 amps. This makes fast charging one of its functions.
RJ-11 – Communication
We are unlikely to find RJ-11 on a device unless it is used for telephone or fax communications. Yes, it’s a telephone socket. It can passively transmit an electrical signal, but some telephone lines carry current that can cause severe injury if you are not careful. Although they are old-fashioned, respect them.
RJ-45 – Communication
An RJ-45 port, more commonly referred to as a network connector, is an 8-pin port for connecting devices to a network using an Ethernet cable. Similar to a phone jack, only slightly wider.
3.5mm TRS Jack – Audio
They are most commonly used for audio devices. Green – for connecting speakers or headphones. Pink is used for microphones. Blue is used to directly connect an audio device. It is also called line-in. There are other types, but they are not common on home devices.
VGA / SVGA video port
The Video Graphics Array (VGA) or Super Video Graphics Array (SVGA) port is used to connect monitors or projectors to a computer. VGA can handle resolutions up to 640×480, and SVGA over 800×600.
Both types look the same. They look like DE-9, but have 3 rows of 5 holes, while DE-9 has a row of 5 and a row of 4 below it.
DisplayPort – Video & Audio
If your computer has a cut-off rectangle slot, that’s DisplayPort. This is a 20-pin video connector. It can also transmit audio over a cable, so if the connected device has speakers, it should also receive audio from your computer.
HDMI – video and audio
The High Definition Media Interface (HDMI) port is very popular. It is also a video port that can also carry audio. They can be found on most computers and televisions.
These are the various physical ports that you are most likely to come across. If the port you are looking at is not found here, there are many resources on the Internet for identifying ports.
Default Ports
There are 65,535 virtual ports and they are all related to network communications. Each of them can be used in different ways, depending on the type of data passing through them. These ports are used for Transmission Control Protocol (TCP) or User Datagram Protocol (UDP), or both.
TCP is often confused with Internet Protocol (IP). You may have seen it as TCP / IP. TCP is used to open a connection between two devices to transfer data. This is achieved due to the fact that one device addresses another, and then a data transfer agreement is concluded between them. This is called a handshake. It can take some time.
UDP does not establish a handshake connection. He just starts the transmission. It’s faster, but since there is no agreement on how to do something, errors can occur.
In theory, any network communication can occur through any port. It’s really confusing when there are thousands of ports available. So we try to follow the standard to make life easier. The Internet Assigned Numbers Authority (IANA) maintains a register of ports and their assignments.
When a communication packet arrives at a computer, it contains information about which port it wants to connect to. This is how the computer can tell you what to do with these packages. This is why you can browse the web, transfer files and print over the same network cable.
You may have seen port numbers used in IP addresses. This will be the number after the semicolon in the IP address, for example 192.168.0.1:8080.
Below is a list of ports you are most likely to come across. We’ve added the last one for all old players.
| Port | Description |
| 20 | FTP (FTP) data transfer occurs on this port |
| 21 | File Transfer Protocol (FTP) control messages sent to this |
| 22 | Secure Shell (SSH) |
| 23 | Telnet |
| 25 | Simple Mail Transfer Protocol (SMTP) for Email |
| 53 | Domain Name System (DNS) |
| 69 | Simple File Transfer Protocol (TFTP) simplified FTP |
| 80 | Hypertext Transfer Protocol (HTTP) |
| 8080 | Alternative Hypertext Transfer Protocol (HTTP) |
| 123 | Network Time Protocol (NTP) for computer time synchronization |
| 143 | Internet Message Access Protocol (IMAP) for email Online Mail |
| 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 emails (SMTP) |
| 515 | Line Printer Daemon (LPD) connects printers to the computer |
| 666 | Doom, First Person Shooter (FPS) |
Ports, ports, and ports…
Now you know about the most common physical and virtual ports and what they do. Bookmark for easy reference or print.
Have any strange ports? Do you have questions about other ports or need more information? Let us know in the comments. We’re here to help.
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