How to Check If UDP Port Is Open and How to Close It

Are you worried about sensitive data and information falling in the wrong hands of cyber thieves? Perhaps you want to make sure about the availability of your network connection with another device. These concerns and many others can cause you to search, how to check if UDP port is open, or maybe look for UDP open port checker so you don’t have to get into the technicalities yourself.

Check If UDP Port Is Open
Check If UDP Port Is Open

In this article, we’re going to make sure we let you know about the basics of data transfer. How UPD port availability can be checked and tested and how to close UDP ports to ensure data security. This way you’ll be able to protect sensitive data from reaching unauthorized computers.

What is a UDP Port?

One of the few data transfer protocols, UDP or User Datagram Protocol port is a network port that allows quick and lightweight data packet movement between host and connected servers. It might sound like UDP port is a physical entity but it isn’t. UDP ports are sometimes considered unsafe as compared to TCP/IP ports and therefore not recommended for encrypted data transfer.

Features of UDP port

Before we talk about how we can check the availability and openness of a UDP port, let’s talk about why people use UDP ports for data transport.

Here are a few features of UDP:

  • Lightweight – The data packets sent with the UDP port are incredibly lightweight and can travel easily over devices.
  • Connectionless – UDP is a connectionless protocol and it doesn’t require a physical connection between various interconnected devices.
  • Fast – Data transfer through UDP ports is significantly faster than other ports and therefore it is used for communicating data such as videos, music, and images, etc.

Demerits of UDP port

Although fast and lightweight, the packets sent over UDP port have a few demerits as well. Here are some of those demerits.

  • Data Loss – The problem with UDP connectionless ability is that you might not receive the data sent over it. It might get lost.
  • Error Recovery – There is no error recovery in UDP transfer, unlike the TCP/IP transfer.
  • Single Transfer – If the connection interrupted, there is no way the data will be sent again since UDP allows only a single transfer at a time.

These are some of the reasons that TCP/IP ports are more often used for data transfer over a large number of connected devices.

How to check if the UDP port is open?

Now to answer the real question, the UDP port connection can be checked in a few different ways. A UDP port that rejects connection is known as a closed port or a port that is safe since nobody can access it. However, if you can send the data over the UDP port. It means that it is available and cybercrimes can occur involving your data if any unauthorized access tries to hack into the network and they can steal your precious sensitive data.

Here are the few ways you can check if your UDP port is open and make sure you close it after data transfer to avoid any security issues.

1. Manual Check

Since UDP port is a connectionless port, it is more difficult to know whether it is open or not. If you choose to manually check whether the port is open or not, you have to write a bunch of code. This process might be technical, but it gets the job done and you get full control over the security of your data.

How this works, is that you have to first open a data packet sniffer, after that you can that packet over the UDP port, if the port returns an error message which says something like “ICMP port unreachable” or “Destination port unreachable”, it means the connection is rejected and that your UDP port is closed.

This will in turn mean that data will not be transferred over the port until it is opened and no unauthorized user will try to get into the network and steal your important data. So, manual checking is a commonly used, slightly technical but majorly effective method for you to check if your UDP port is open.

2. Utility Tools

If this is difficult for you and you want to take an easier approach towards network testing, then you can use various free and paid network utility tools that offer network checking services and make sure you know when your network is open or close.

There are many different kinds of network utility tools on the internet that you can download and then connect to their server and they will display the activity of your network. If the network is closed, they will display a message and if the network is open, the tool was let you know, ensuring maximum data security in regards to User Datagram Protocol.

3. UDP open port checkers and scanners

These scanners can work on both the client and the host machine at the same time. They are also very commonly used to identify whether the UDP port is open or not. A multitude of UDP port checkers and scanners are available on the internet. This software actually uses raw data packets to transfer over multiple networks to check the availability of that network. If the data packet doesn’t arrive at the destination and instead displays a connection error, you can conclude that the port is not open and data is safe.

4. Online port checkers

Another fairly easy and usually free of cost method of checking the availability of your network UDP port. Is through online port checkers – like our site. These websites ask for your port number and then, try sending data packets from the source device to the destination over that UDP port.

In turn, check the connection. If the connection is rejected and data is lost. The webpage displays the result showing that the port is closed.  You can stay calm about the security of your data without the hassle. without the need of downloading multiple files and utility tools hogging up your device storage.

All these methods are very effective when it comes to checking the data transfer availability of your network’s UDP port. Once verified, you can move on to closing the port if it is still open.

How to Close Unused UDP Ports?

We’ve established that we can identify the availability of UDP ports. But how do we close an open but unused port? Doing that to avoid potential data loss and security concerns?

Let’s find out:

There are a few ways of actually blocking the web or FTP UDP ports that you might have been using in the past for some file transfer and now they are abandoned and unused.

Here are those few methods in detail:

Windows Defender Firewall

Windows Defender
Windows Defender

A method that is strictly available for Microsoft Windows users only, the Windows defender firewall allows you to close any unused ports so that your corporate data can be protected from network theft.

What you have to do is, open the Windows defender and go to the advanced settings tab. Here you will be presented with an option called “Inbound Rules”. Which contains the default system rules of the defender firewall. From here, select the New rule option and click on the port.

Meaning that you would like to create a rule about the TCP/IP or UDP port. Now, you are supposed to click on UDP and give the number of the port that you want to close. Then you click on next and block the connection radio button must be checked. You have successfully closed your unused UDP port.

Linux Command Prompt

This method is apt for terminating your UDP port connection if you’re using the Linux operating system. This requires you to open the command server in order to type instructions.

Once the command server is open, you are supposed to initiate a terminal session. The command that we’ll be using is the netstat command. You need to write netstat –tulpn and run the command.

This command will list all the services listening for the network traffic for your particular port. You need to be searching for the process id of the port which is in the last column.

If you have difficulty seeing the id’s. You can use the grep “:port number” command which will show the port and its connection properties. Now that you have all the servers and their process id’s listed. You can use the specific command required for disconnecting the port. You can do this by typing “service” then the name of the port and “stop”. Which will allow you to close the service that is using this UDP port.


netstat –tulpn | grep “:443”

Ubuntu netstat command
Ubuntu netstat command

Although this method is time taking, you will be able to close your UDP port and ensure your data safety.

All your queries regarding checking and testing the availability of UDP ports. This along with the methods of closing them to avoid data security issues have been accurately addressed. Now that you have learned all the required methods. We hope that your data will remain secure and you will not face any network connectivity concerns.

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