The Specified Port is Already Open VPN Error: 4 Quick Fixes

by Radu Tyrsina
Radu Tyrsina
Radu Tyrsina
CEO & Founder
Radu Tyrsina has been a Windows fan ever since he got his first PC, a Pentium III (a monster at that time). For most of the kids of... read more
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  • The specified port is already open error can prevent you from using your VPN client.
  • Port conflations are a common cause for this error, so you'll have to prevent apps from using certain ports.
  • One way to fix the issue is by modifying your registry, so be sure to try that as well.

It isn’t uncommon to encounter a series of error messages while using a VPN on your PC. However, the specified port is already open error seems to be predominant with Sonicwall VPN’s NetExtender. 

Many users have also reported that they got this error after updating their windows to the newer versions. This problem can affect various clients, and many reported that SonicWall VPN stopped working due to this error.

Although this error can be caused by many reasons, its major cause stems from any attempt by another application on your device to open a non-sharable network connection port used by the VPN. 

While this guide will attempt to provide solutions, we’ll first explore the possible causes of the VPN error if the specified port is already open. 

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What causes the specified port is already open error when using VPN?

Computer sleep mode activated due to inactivity. When a VPN is actively running and the PC goes to a sleep mode because of inactivity, the non-sharable connection is still locked. As such, the reestablished connection pops up the error after the user reawakens the PC.

Secondly, the error message could also occur if another application attempts to use the same port as the non-sharable connection used by the VPN. 

Although this is more associated with Mac and Linux, SSH forwarding could prompt this error message. Both Meraki and SonicWALL VPN users reported The specified port is already open, but you can experience it on other VPN clients.

In addition, software bugs and lags due to computer updates could be another reason why this VPN error message may come up. 

Hence, these are the basic troubleshooting fixes to solve this error.

How can I fix specified port is already open VPN error on Windows 11/10?

1. Restart the PC

  1. Click the Start button.
  2. Click the Power button. Now select Restart.
  3. Wait for your PC to reboot.

Although this is a basic fix, it is one of the most efficient methods to troubleshoot most PC problems. The locked connection is closed after a reboot and the VPN can create a new connection. 

So be sure to try this method if you’re getting VPN error The specified port is already open on Windows 11.

2. Use the Registry Editor

  1. Press the Windows key + R, input regedit in the box, and press Enter key. 
  2. In the Registry Editor, navigate using the following path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
  3. Right-click the right pane, choose New, and select Multi-string Value
  4. Rename it to ReservedPorts and open it. 
  5. Input 1723-1723 in the Value data box and click OK. 

  6. Close and restart the PC to take effect. 

By editing the registry, you might fix VPN The specified port is already open when using L2TP protocol, so be sure to try this method.

3. Modify connection port in Command prompt

  1. Press the Windows key, search for command prompt and select Command Prompt from the list of results.
  2. Input the following code: netstat -aon 
  3. Identify process PID for any program using port 1723.
  4. Input the following command and press Enter key. We used this command as an example, but you’ll need to change the number at the end so it matches your process: taskkill /F /PID 1242
  5. Close Command Prompt.
  6. Restart PC to take effect. 

This is a forceful attempt to stop an app from using the VPN’s dedicated port, and it can help you if you’re getting The specified port is already open error when using PPTP protocol.

4. Use the Control Panel

  1. Press the Windows keysearch for control panel and launch it.
  2. Change the view by to Small icons and select Phone and Modem. 
  3. Open the Modems tab, choose the modem and click Remove. 
  4. Restart PC to take effect. 

This fix is for modem-related issues that cause VPN the required port is open problem on Windows 11/10. 

How can I fix VPN The specified port is already open on Windows 10?

All Windows versions are similar in terms of functionality and settings, so most features work exactly the same on almost versions.

The same goes for VPN, and if you’re having this issue on your Windows 10 PC, you’ll be pleased to hear that you can use all the solutions from this guide to fix it.

These are the best fixes for this VPN error message. If none works for you, Check out our comprehensive guide on VPN errors on Windows 10/11

Also, our article on VPN troubleshooting may provide you with additional information on how best to solve your VPN issues. 

However, if your VPN has stopped working altogether, read this guide on what to do if your VPN stops working

We’d like to hear from you in the comments section below. 

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