Verify that you have given Crouzet-Soft permission to access the PLC. Specifically, enable “Allow an app through Windows Firewall.”
This article is part of the DigiKey Field Guide for Industrial Automation
Location: Program It → PLC.
Difficulty: 
Student — difficulty levels explained
Author: Aaron Dahlen | MSEE | Senior Applications Engineer, DigiKey, Author bio.
Last update: 24 Aug 2026
Figure 1: Crouzet PLC situated on the author’s workbench.
Procedure
On my workbench is the Crouzet MXD12SD1ET PLC (Figure 1). On my PC is the latest edition of Crouzet-Soft.
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Connect the PC to the PLC. They may be directly connected via a straight-through cable, switch, or home router.
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Verify that you can ping the PLC. Set the IP address on the PLC as necessary. The featured PLC makes this easy as the IP address and subnet mask can be set via the user display and local pushbuttons.
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From the Windows Start button, launch “Allow an app through Windows Firewall”. Verify that Crouzet-Soft has permission as shown in Figure 2.
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Verify that Crouzet-Soft and the PLC can communicate.
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Have fun!
There may be other reasons Crouzet-Soft cannot communicate with the PLC. The TechForum community may be able to assist if you leave your description in the comments below.
Figure 2: Enable Crouzet-Soft in the Windows Defender Firewall.
Parting Thoughts
Because I was able to ping the PLC, I assumed a valid connection between Crouzet-Soft and the PLC. This was false as the ability to ping is not the same as the ability to pass through Windows Defender. The challenge was to stop and think about the problem from a different perspective.
Note that there are other ways to pass through the firewall. What I’ve presented in this note is a simple way to solve this problem. Work with your IT department for alignment with your company’s policy.