Chances are, you stumbled upon this article because the application you are trying to launch complains about a “port” blocking, or you read that leaving certain “ports” open on your network can be a security issue.
In any case, by the end of this article, you will not only know what these ports are that everyone is talking about, but also how to check your computer for open or closed ports.
What is the network port?
The first thing you should know is that the ports we’re talking about are virtual . This has nothing to do with the physical ports of the network equipment on your router, TV, consoles or computers. Ports are simply a way for your network hardware and software to organize information traffic.
Imagine the reserved lanes on the road. Sidewalk for pedestrians. There may be a designated cycle lane. Road trains and buses also have their own lanes. Ports serve the same function. One port can be used to receive e-mail and the other can be used to transmit file transfer requests or website traffic.
There are two common types of ports that require a brief explanation before we move on to checking which ports on your system are open and which are not.
What are the TCP and UDP ports?
The two common types of ports on modern networks are known as TCP and UDP ports. These are the transmission control protocol and the user datagram protocol respectively. Thus, these two types of ports use different network protocols.
Which you can think of as special sets of rules for how bits of information should be sent and received. Both types of ports are built on the fundamental Internet Protocol (IP) that makes the Internet and home networks, well, run . However, they are suitable for different applications.
The big difference is that when you are sending information over UDP, the sender does not need to first establish a connection with the receiver before starting a conversation. It’s a bit like sending a letter. You don’t know if the other person received your message, and you cannot guarantee that you will receive a response.
TCP, on the other hand, is more like a phone call. The recipient must “intercept” the connection, and information will be sent back and forth until someone hangs up.
UDP messages are typically sent over the network to anyone listening on a specified UDP port. This makes it ideal for service messages related to the operation of the network itself. It is also ideal for VoIP streaming, online video games, and live streaming.
Why? These applications benefit from low UDP latency and a constant stream of information that doesn’t have to be perfect to be useful. After all, a little damage to your Skype chat is far less important than a little lag.
TCP is much more prevalent than UDP and absolutely guarantees that all data is received without errors. Pretty much anything that doesn’t require the special benefits of UDP uses TCP instead.
Which ports are normally opened by default?
There are a LOT of ports. The port number can be anything from 0 to 65535! This does not mean that any application can simply select any port. There are established standards and ranges that help us make sense of noise.
Ports 0-1023 are associated with some of the most important and fundamental network services. This makes sense since the lower numbered ports were assigned first. For example, SMTP for email is used exclusively on port 25.
The rest of the port numbers are known as “dynamic” or “private” ports. These ports are not reserved and anyone can use them on the network to support a particular service. The only problem occurs when two or more services on the same network use the same port.
While it is not possible to list all the important ports, these common ports are good to know by heart:
- 20 – FTP (File Transfer Protocol)
- 22 – Secure Shell (SSH)
- 25 – Simple Mail Transfer Protocol (SMTP)
- 53 – Domain Name System (DNS)
- 80 – Hypertext Transfer Protocol (HTTP)
- 110 – Post Office Protocol (POP3)
- 143 – Internet Message Access Protocol (IMAP)
- 443 – HTTP Secure (HTTPS)
- The first thing you want to do. open the start menu and search for CMD.
- Now right click on CMD and select “Run as administrator”.
- At the open command prompt, enter:
- Don’t worry about the long list of information scrolling faster than you can read it. You can simply use CTRL + C and CTRL + V to copy and paste the information into Notepad or any other text editor.
- The information in brackets is the name of the program using the port. TCP or UDP refers to the protocol used on this port. The number consists of an IP address and a port number after a colon.
- Open the Start menu again. and find CMD.
- Right click on CMD and select Run as administrator.
- At the open command prompt, enter:
- Open the start menu and search for CMD.
- Now right click on CMD. and run as administrator.
- At the open command prompt, enter:
Since there are many thousands of generic port numbers, the easiest way is to remember the ranges. Which will tell you if a given port is reserved or not. Thanks to Google, you can also instantly see which services are using a particular port.
Find open ports in Windows
Now that we have all the basic knowledge about TCP and UDP ports, it’s time to start looking for what ports are open and in use on your computer.
The good news is that Windows has a pretty useful command built in to show you which ports are currently being used on your computer by various applications and services.
Search for blocked ports
This allows us to determine which ports are in use by which application, but does not tell us which ports are actively blocked by Windows Firewall.
Netsh firewall display status
This is a mapping of blocked and open ports according to your Windows firewall configuration.
You will see a note that this command is deprecated, but the new command does not show us the information we need. So for now, using the show state command is still the fastest and easiest way to get port information.
Just because Windows Firewall is not blocking a port does not mean that your router or ISP is not blocked. Therefore, the last thing we want to do is check if any external locking is happening.
netstat -ano | findstr -i SON_SENT
If there are no calls in the list, then nothing is blocked. If some ports are listed, it means that they are blocked. If it shows a port not blocked by Windows, you can check your router or send an email to your ISP if switching to another port is not possible.
Useful apps to map your port status
While the command line is a good quick and dirty tool, there are more advanced third-party applications that can help you get an idea of ??your port configuration. The two highlighted here are just popular examples.
SolarWinds requires you to provide your name and details in order to download it, but it is up to you whether you provide your real information on the form or not. We tried several free tools before settling on SolarWinds, but it was the only tool that worked properly on Windows 10 and had a simple interface.
In addition, he was the only one who did not fly a false positive virus flag. One of the major problems with port scanning software is that security companies tend to view it as malware. Therefore, most users ignore any virus warnings that come with such tools. This is a problem because you cannot distinguish a false positive from a real virus in these applications.
SolarWinds may come with some strings attached, but it actually works as advertised and is easy to use.
As you can probably guess, this is a website service, not an application. This is a good first port to check if external data can pass through your local port or not. It automatically detects your IP address and all you have to do is specify the port to test.
It will then tell you if the port is blocked or not, and you will need to find out if the port is blocked at the computer, router or service provider level.
Most users don’t need to worry about ports. They are controlled by your operating system, applications, and network hardware.
However, when things go wrong, it’s good to have a tool close at hand that allows you to find open ports to track down suspicious activity or figure out exactly where your precious information hits a brick wall.