All computers, whether they are laptops or desktop PCs with Windows, Mac, Linux or any other operating system, have input and output ports. These ports can be physical and visible on the back or sides of the computer itself or even virtual ports that are perhaps more difficult to understand.
In this little computer lesson we see the difference between physical and virtual ports, trying to understand above all what the latter are and what it means when you hear about a door referred to a software or a system like Windows .
The computer doors are exactly like the doors of a house even if they can be only input (input), only output (output) or both .
The physical ports are easy to understand because they are the ones to which the PC cables are connected.
For example, the monitor port (which can be VGA, HDMI or other) outputs the video signal from the graphic card to the screen, while the audio port outputs the sounds from the speakers connected by cable to the computer.
As both input and output ports we can take the example of USB ports, which can be used bidirectionally to transfer data to the computer or from the computer to another device (such as a smartphone).
In another article we have described the main ports, sockets and connectors for cables of a computer, with different insights on all types of USB ports.
The virtual ports are also input and output and serve as network addresses for the computer to receive and transmit data to other computers or the Internet.
These ports are used by network devices to interact with each other, they can be used by specific programs to send data or they remain open to listen to incoming requests.
Network ports are simply indicated with numbers, which side by side with the computer's IP address allow the router to know where a data packet comes from and to which program it should be sent.
The router is the device that manages the inputs and outputs through the virtual ports, to direct traffic to the different devices on the network.
For example, if you need to use a network printer and send a document to be printed, the router will send the command to the printer through the internal ports.
Another example of a port, the more banal one, is that of the internet browser which works on port 80 for http requests.
In practice, the web browser, when it has to download a website like this, connects to the server where the pages of the site are located through port 80.
As already written in the guide to Internet addresses, network protocols and ports, to understand what ports actually are, you can think of the parcel delivery system.
Thinking about the computer network as a road network, to IP addresses such as street names and doors such as house numbers, it is easy for a courier (who becomes our router) to know who should send a parcel or from whom he has to pick it up to take it somewhere else.
The virtual ports on the computer are opened by specific services and programs when they are running.
The doors are recognizable by numbers, from 0 to 65536, which can be decided by the program developer or by those who use it.
Virtual ports cannot be damaged like physical ports, but they represent security risks for the systems to which they belong and must therefore be managed by the router.
In other articles we have therefore seen several guides on the subject:
- How to open the ports on the router, to allow the computer to use programs such as Torrent clients, which need to send and receive data on the internet.
- How to block ports on Windows PCs to prevent hackers or viruses from transmitting computer data externally.
- Programs to see in real time the use of the ports in the internet connection, to see which are open and which are listening ready to receive.
This operation can also be done without programs, on Windows, by opening the command prompt (with administrator rights, then opening it by pressing on it with the right mouse button and running it as administrator) from the Start menu.
The command to send to control the use of virtual ports on a Windows PC is: netstat -ab
The result of the command may take a minute or two to fully display.
Ports are the number after the colon in the local address column, for example: 127.0.0.1:3213 3213 is the port.
When it is written that the door is in Listening , means that it is listening but not in use, while if it is written Established it means that it is actively connected.
To get a clearer view of the ports in use on your computer, you can use the netstat -aon command
In the list that comes out you can find the PID, the identification number of the process that uses that port.
To find which program or service uses the port, you can then open the Windows task manager to see the list of active processes and associate the PID with the name of the program.
A program like Currports makes it easier to see open and listening ports on Windows.
On this site you can check if a door is open and is communicating on the internet.
Most network attacks on computers try to look for open and unsecured ports and when Windows still did not include a firewall (like on Windows XP), these attempts were often successful.
Furthermore, any attacks on the ports via the internet are immediately prevented by the routers, which by default keep all the ports closed (for this reason, the guide to open the ports on the router is necessary as seen above).
With modern systems, from Windows 7 to Windows 10, it is possible to control the transmission of data on the ports through the Windows Firewall
The most common remedy in this case is often a firewall that limits the traffic / information passing through a port. A firewall can generate several false flags which is better than letting something malicious slip through. Firewalls on your system and on your network are needed to make sure your virtual ports are secure.
Fortunately, it is not easy to open a virtual door. Dedicated open ports are already in use by the router or another device. All other ports are closed by default and must be opened with command line utilities or other similar tools.
