Emsa Port Blocker - TCP Port Blocker and Viewer for Windows

Windows Utility
Operating Systems supported: Windows XP, Windows Vista, Windows 7, Windows 8, Windows 8.1, Windows 10

Current version: 1.2.39 -      (zip file, 334 KB)       

Installation Notes:
  • VB Runtime (rare): This product requires the VB6 Runtime. On most Windows Systems (XP and above), it is already installed so there's nothing to do. However, if you receive any error messages when launching the program after install, please download and install the runtime from Microsoft (1MB). Reboot if asked.

Product Information:

IMPORTANT: An improved version of this program is now available! Check out the fresh, highly improved Advanced Port Blocker (new site)

Emsa Port Blocker is a TCP blocking utility. What it does, is blocking unwanted tcp access from/to your computer. It is not a firewall, but works in a similar fashion. Its purpose is to prohibit TCP access on certain ports and ip addresses. IT can also be used as a TCP monitor because it shows TCP connections currently active on the machine.

Windows 10 - Important: You need to always run this program as an administrator in order to function properly. Look at the bottom of this page, in the "Windows 10 setting" section for instructions.

This program works two ways. It can be configured to block access to certain local ports, but it can also prohibit access to specified remote ports as well. For example, you may try adding the port '80' to remote blocked ports. You'll immediately notice that you have disabled your browser's capability from accessing the www. You can use this program to block unauthorized access to certain ports on your computer, for example network ports like TCP 135 or 139 and so on. You can also use the configuration to permit connections between local IP's, or block even those as desired. The program comes with a function allowing to detect local ip's and adding them to the 'allowed' IP list.

- When first started up, the program shows a list of TCP connections on your machine.If you don't see anything there, try opening browser and visit some site and you'll see them.
- By unchecking the 'Show only connected' checkbox the program will also show tcp connections in other states, like LISTENING and so on.
- The left hand list is versatile and its meaning depends on the last button clicked - check the label above to see what the list is currently displaying.
- To add items to a particular list, type into the textbox below and click on add. Make sure you enter valid data (valid ip addresses/ valid port numbers).To delete one item, select it in the list and click on 'Delete'.
- To view Allowed IP Addresses, click on the corresponding button. By default, here you will see your local IP address ( You may want to add all your local IP addresses to the allowed list. To do that, click on the 'Add local IP's to Allowed' button. Then go to 'Allowed IP Addresses' and you will see them. You may preview which are your local ip addesses by clicking on the 'Local IP Addresses' button.
- To block a local port, click on 'Blocked Local Ports' and add one item to the list. For remote ports, same thing, using the 'Blocked Remote Ports' button.
All settings take effect immediately and the configuration is also automatically saved in registry.

An additional use of this program could be the case when you have to remotely deploy a software firewall on a remote computer. In most cases you can't do that - because what would happen is that the firewall asks for reboot after installation, and then you'll permanently loose connection to the machine. By default,firewalls are set to learning mode, so at the next boot you will no longer be able to acces the machine! So then you will have to ask someone to log into the machine directly and configure or at least disable the firewall so you can get back in. If your need is to block certain TCP ports, our program may be used as a temporary solution until you manage to properly deploy a firewall on the remote machine.

Finally, an explanation on how the blocking works with this program. As long as the program runs, it constantly monitors the TCP connection table for changes. This is done each milisecond or so. Whenever a new client has connected, it checkes this against its current rules, and if a blocked port is used, it will immediately send command to the operating system to instantly terminate the connection. As you can see, this program is not a firewall, this giving it some advantage in certain cases, which is that can usually be used on a machine with an existing firewall, if you don't want to reconfigure your firewall and find this tool usable for some purpose. We recommend testing it thoroughly to see if it fits your purpose. Keep the program running and minimized in systray to benefit from port protection.

Installation Notes:
This program is provided as an installer executable. To install, follow the wizard instructions carefully. To uninstall, use the Add/Remove programs feature in Control Panel.

Windows 10 setting

This product works just fine on Windows 10, but you have to do the additional settings below (run as an administrator). ( On Windows 7 and Windows 8.1 this is recommended but not mandatory ):

Here is how to set it to run as an administrator (for all users on your PC):

  • 1. Go to program installation folder, usually C:/Program Files(x86)/Emsa Port Blocker
  • 2. Right-click on PortBlocker.exe and select Properties
  • 3. Go to "Compatibility" Tab, then click on "Change settings for all users"
  • 4. Check "Run this program as an administrator", click Apply and OK, then OK again.
  • 5. Close and restart Port Blocker.
That's it - you're done! Port blocking should run fine now.


If the program does not show the connections list OR does not block remote ports, please make the compatibility settings in the "Windows 10 setting" above. This should normally fix the issue.


Version 1.2.38: Critical bug fix - Fixed an issue that could cause connections list and port blocking to work intermittently. All customers with older versions and 1.2.38, please upgrade now to the latest version as this is an important fix.


If you have suggestions, bugs spotted, requests for new features, please email us. Thanks!

System requirements
Any usual Windows machine with a couple mbytes of free disk space will do.

License Information
Please read the license.txt for licensing information.

Emsa Port Blocker: TCP Port Blocker and Viewer for Windows: Windows Utility

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