Windows Firewall for Network Camera Access

Some cameras that fluxEngine can talk to are reachable via the network. In order to be able to receive data from these cameras, exceptions must be added to any firewall software so that fluxEngine can receive the image from the camera.

In general an exception must be added with the following properties:

  • Application: fluxDriverIsolation.exe (the path that will actually be used)

  • Protocol: UDP

  • Port: any

  • Direction: incoming

The specific binary fluxDriverIsolation.exe that comes with fluxEngine must be chosen for the firewall rule. See Driver Isolation Framework for further details on where this file is located.


A typical error message that may occur when a firewall rule is not present is:

Could not negoatiate packet size.

Testing if the firewall is causing the issue

In order to quickly verify that it is indeed the firewall that is causing issues for fluxEngine being able to connect to cameras, temporarily disable the firewall completely and attempt the connection with fluxEngine again. If that solves the issue, the firewall is blocking the connection. In that case reactivate the firewall (to avoid leaving the system vulnerable) and add a specific rule for fluxEngine.

Windows Defender Firewall

In this section there is a step-by-step tutorial for adding the firewall rule to the fluxDriverIsolation.exe that has been installed together with the fluxEngine Python package, when using Microsoft’s Windows Defender firewall. (If a customer uses a different firewall, please consult the documentation of that firewall for further details.)

If Python for Windows is installed in a user-specific directory, fluxDriverIsolation.exe will be found under:


If Python for Windows is installed for all users, the binary will be found under:

C:\Program Files\PythonVERSION\Lib\site-packages\fluxEngine\fluxDriverIsolation.exe


In the case of C/C++, the fluxDriverIsolation.exe binary location will vary depending on the development and delpoyment setup of the user (see Driver Isolation Framework), and they must add such a rule for each location of fluxDriverIsolation.exe that is relevant.

Step 1: Open the Windows Defender Firewall settings

Go to the start menu and start typing Windows Defender Firewall with Advanced Security. The following entry should be shown:


If the Windows installation is in a different language, the name of the settings application will be slightly different.

Step 2: Add a new firewall rule

Go to the menu Action and select New Rule... to create a new firewall rule:


Step 3: Indicate that a program-based rule should be added

In the first wizard, select Program to indicate that a rule specific to a program should be added to the firewall:


Step 4: Select the fluxDriverIsolation binary

Select the fluxDriverIsolation.exe binary from the directory. Note that C:\Users\USERNAME\AppData may not be visible in the File Explorer in the default settings.


Ensure that the file name is correct in the second page of the rules wizard:



Windows will by default replace parts of the path with variables such as %SystemDrive% or %USERPROFILE% after closing the file selection dialog. If that happens it is essential that that path is replaced by an absolute path; especially when %USERPROFILE% is specified in the rule the rule will not work properly. (The screenshot shows a correct path that includes a drive letter.)

Step 5: Proceed with the wizard

Indicate that the connection should be allowed:


The rule should apply to all profiles:


(If a user knows what they’re doing they may restrict the profile to a specific one, but which profile Windows assumes a network connection to be associated with may not be 100% stable, so allowing this for all connections is recommended.)

Finally, specify a speaking name for the rule:


Step 6: Verify the program path in the rule settings

After rule creation please verify that the rule wizard has not replaced the absolute path that was specified with %USERPROFILE% again (which would cause the rule to not work). To do so, right-click on the newly created rule and select Properties:


Then go to the tab Programs and Services and verify that the specified program does indeed have an absolute path that starts with a drive letter (e.g. C:\):


Optional: Restrict the rule to only UDP

This is optional.

All cameras that are supported by fluxEngine so far use UDP-based protocols for the network communication, so it is possible to restrict the protocol type in the Protocols and Ports tab of the rule properties window to UDP (instead of All Protocols):


Note that the ports should never be restricted, as many network camera protocols use dynamically assigned port numbers.