US What a computer port is
Computer ports are the physical sockets on a computer’s case or motherboard where cables connect it to peripherals, displays, networks and power. Each port combines a connector shape with an interface standard, and it is the standard, such as USB 3.2 or HDMI 2.0, that decides how fast the port runs and what it can carry.
The word “port” has a second meaning in networking. A TCP or UDP port is a number that identifies a service on a networked device, such as port 443 for HTTPS. That is a software address, not a socket, and it is not what this guide covers.
Ports fall into a few families: data ports for peripherals, network ports, display outputs, audio jacks and, on older and industrial machines, legacy and control ports. Desktop PCs, laptops and industrial computers mix these families differently because they are built for different jobs.
Types of computer ports
The table below covers the ports you are most likely to find on a desktop, laptop or industrial PC. Speeds are the headline figures from each standard; real throughput is usually lower.
| Port | Connector | Typical speed | Common uses |
|---|---|---|---|
| USB-A | Flat rectangular | 480 Mb/s to 10 Gb/s | Keyboards, storage, cameras, dongles |
| USB-C | Reversible oval | Up to 40 Gb/s (USB4, Thunderbolt) | Storage, docks, displays, charging |
| Ethernet | RJ45 or M12 | 1 to 10 Gb/s | Networks, IP cameras, PoE devices |
| HDMI | 19-pin HDMI | 18 Gb/s (2.0) · 48 Gb/s (2.1) | Monitors, TVs, signage |
| DisplayPort | 20-pin DP | 32.4 Gb/s (1.4) | Monitors, daisy-chained displays |
| VGA | DE-15 D-sub | Analog video | Legacy monitors and KVM switches |
| Serial (COM) | DE-9 D-sub | Typically up to 115.2 kb/s | PLCs, instruments, scanners |
| Parallel (LPT) | DB-25 D-sub | Up to around 2 MB/s (IEEE 1284) | Legacy printers, CNC and lab equipment |
| Audio (aux) | 3.5 mm jack | Analog audio | Speakers, headsets, line-level audio |
USB is the port most people mean by “computer ports”, and it now covers five speed grades and two connector shapes. Our history of USB in industrial applications explains how the generations fit together.
Display ports deserve a second look when specifying a system. HDMI suits TVs and signage screens, DisplayPort suits multi-monitor desks and high refresh rates, and USB-C can carry DisplayPort as well as data and power. On industrial boards, internal LVDS or eDP headers drive built-in panels instead of an external port, which is how panel PCs connect their own screens. Counting the outputs you need, and the resolution of each, before choosing a computer avoids adding a graphics card later.
Legacy ports: parallel, PS/2 and aux
Some ports have vanished from consumer PCs but still matter to anyone maintaining older equipment.
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Parallel port. A female DB-25 port, standardized as IEEE 1284 and named LPT1 by the operating system. It sends eight bits at once over eight data lines, which made it the printer port of the 1980s and 1990s. USB replaced it, but some industrial motherboards still offer one for CNC controllers, license dongles and laboratory instruments.
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PS/2. Six-pin mini-DIN ports for a keyboard (purple) and mouse (green). They remain on some industrial boards because they work without USB drivers during early boot.
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Aux port. On a computer, the 3.5 mm line-level audio jack. On network routers, an auxiliary port is a second serial console port used for out-of-band access through a modem.
Ports on industrial computers
An industrial PC is chosen by its I/O as much as by its processor, because it has to connect directly to machines, sensors and vehicles rather than to a keyboard and a monitor. Beyond the usual USB and display outputs, embedded box PCs typically add the ports below.
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Several Ethernet ports. Two to eight LAN ports separate machine networks from the plant network, often with PoE to power cameras directly.
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Serial COM ports. RS-232, RS-422 and RS-485 ports for PLCs, drives, meters and instruments, usually on DE-9 connectors.
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Isolated digital I/O. Inputs and outputs that read sensors and switch relays directly, isolated from the computer’s ground. Our guide to how GPIO pins connect to sensors and actuators covers the basics.
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CAN bus. Vehicle and machine networks for engine data, telematics and robotics.
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Power and control. A wide-range DC terminal block, a remote power switch input and, on in-vehicle computers, ignition sensing that starts and shuts down the system with the engine.
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Expansion and wireless. M.2 and mini PCIe sockets for Wi-Fi, 4G or 5G modems and storage, with SIM slots and SMA antenna ports.
Quick answers on computer ports
Computer ports: common questions
What are the ports on a computer for?
Connecting everything outside the case. Ports link a computer to peripherals, displays, networks, audio devices and power, and on industrial PCs to machines and sensors.
What are the different types of USB ports?
Two connector shapes and several speeds. USB-A and USB-C are the common connectors on computers, and speeds run from USB 2.0 at 480 Mb/s to USB4 at 40 Gb/s, as defined by the USB-IF.
What is a parallel port?
A 25-pin port that sends eight bits at once. It was the standard printer port before USB and is now found mainly on industrial boards for legacy equipment.
What is an aux port?
An auxiliary audio input, usually a 3.5 mm jack. It carries analog line-level audio between a computer, speakers or a car stereo. On network routers, an aux port is a backup console port.
How many ports does a computer have?
It varies widely. A thin laptop may have two or three USB-C ports, while an industrial box PC can carry six or more LAN ports, several COM ports and digital I/O.
We specify and fit the I/O each installation needs as standard, adding serial, LAN, PoE or wireless cards where the base system falls short, and test every port before the system ships. Send us your device list and we will match the ports to it.