How to Check If a Port Is Open in Windows 10

This article outlines how to check for open ports in Windows 10, which is necessary if an application cannot access the internet or you want to block an application.

How to Check If a Port Is Open With Netstat

The easiest way to check if a port is open on Windows 10 is by using the Netstat command. 'Netstat' is short for network statistics. It will show you what ports each internet protocol (like TCP, FTP, etc.) is currently using.

The command has many parameters, but the ones you'll need to use to check if a port is open are (a), which provides the active ports, and (b), which will tell you the name of the processes using those ports.

1. Select the Start menu and type "command." Right-click on the Command Prompt app and select Run as administrator.

2. Type netstat -ab and press Enter. You'll see a long list of results, depending on what's currently connecting to the network. You'll see a list of running processes. The open port numbers will be after the last colon on the local IP address (the one on the left).

3. Look for the items on the list with a state of "LISTENING." These are the processes that are communicating via one of the currently opened ports.

4. If you want to know the program's name that has a specific port open, then type netstat -aon and press Enter. This command will show the protocol the app is using, the local and remote IP addresses, and most importantly, the PID of the application using that port (the number on the far right). Remember to look for the LISTENING status.

5. To find the application related to that PID, right-click the task manager and select Task Manager. Select the Details tab. Look in the PID field for the PID you noted from the command prompt screen.

How to Check If a Port Is Working Using Third-Party Apps

If you don't want to use the command prompt to check for open ports, there are very easy-to-use third-party apps that can help.

TCPView

TCPView is a utility included in Microsoft Sysinternals that shows you a list of all running processes and their associated open ports. This app displays ports opening and closing and packet transfers, all in real-time.

Nirsoft CurrPorts

Nirsoft CurrPorts is another utility to see all ports currently being used by applications and services on your system. Just look for the local ports column to see which of your computer's ports are active.

The list also includes ports that are being connected to on the remote end (the server out on the internet).

PortQry Command Line Port Scanner 

Install PortQry Command Line Port Scanner for another command-line utility dedicated to scanning your computer for open ports. Once you install it, open Command Prompt in administrator mode. PortQry automatically installs in the C:\PortQryV2 directory, so change the directory of your command prompt to that directory.

Type the command portqry.exe -local to see all open TCP and UDP ports for your machine. It'll show you everything you can see with the NetStat command, plus port mappings and how many ports are in each state.

What Is a Port?

Applications running on your computer reach out and get information and data from servers elsewhere on the internet. These applications and the server know how to communicate based on their IP address and the port number.

Think of the IP address as a street address and the port number as the apartment number. If either the server or application attempts to communicate using any other port number, it won't work. Every other door will be "locked" because other ports are closed.