Rapid SCADA can reject the MQTT device library even when .NET Framework 4.7.2 is installed correctly. In the reported case, Windows had marked KpMqtt.dll as originating from a network location. Unblocking the DLL resolved the failure on both Windows Server 2012 R2 and Windows Server 2016.
Identify the MQTT Library Load Failure
ScadaCommService 5.2.1.2 started but failed while loading KpMqtt.dll. The decisive messages were Error getting device logic type from the library KpMqtt.dll, System.NotSupportedException, and the warning that the assembly came from a network location. Rapid SCADA then reported No active communication lines and Normal program execution is impossible.
Load device library: KpMqtt.dll
Error creating communication line 1
Error getting device logic type from the library KpMqtt.dll
An attempt was made to load an assembly from a network location
No active communication lines
Normal program execution is impossibleSeparate the DLL Block from the .NET Version
The identical error occurred on Windows Server 2012 R2 and Windows Server 2016 after .NET Framework 4.7.2 installation. Although Windows components displayed the original 4.6 entry, a separate installed-version check confirmed 4.7.2. Therefore, the component-list display did not establish that the newer framework installation had failed.
The exception text identifies assembly trust or origin as the relevant condition. Do not treat this message as proof of an MQTT driver and .NET Framework version mismatch.
Unblock KpMqtt.dll and Verify Operation
- Stop the affected Rapid SCADA communication service before changing the library file.
- Open the Windows file properties for
KpMqtt.dlland apply the available unblock action. - Restart the communication service and start the MQTT communication line.
- Verify that the log no longer reports the network-location exception, that communication line 1 is created, and that the service does not report zero active communication lines.
The unblock action restored operation in the reported configuration. The evidence does not establish that editing a .NET configuration file to enable loadFromRemoteSources is required when the DLL can be unblocked directly.
Select the MQTT Driver Version
| Driver | Evidence-based decision |
|---|---|
| 5.0.4.0 RU | Older candidate; no advantage was identified. |
| 5.3.1 RU | Recommended as the newer 5.x driver. |
| Version 6 MQTT driver | Reported as fully reworked for improved reliability and usability. Migration depends on whether the project's module set supports version 6. |
For a version 5 installation, select 5.3.1 RU over 5.0.4.0 RU. Version 6 beta4 exposed driver configuration through XML files, while a driver user interface was planned for the following beta release; treat those beta-specific details as historical and verify the capabilities of the exact build under consideration.
FAQ
Why does Rapid SCADA reject KpMqtt.dll after installing .NET Framework 4.7.2?
If the log says the assembly came from a network location, Windows has blocked or restricted the DLL based on its origin. Unblock KpMqtt.dll, restart the communication service, and confirm that the MQTT line is created.
Does seeing .NET Framework 4.6 in Windows components mean 4.7.2 failed to install?
Not in the reported Windows Server 2012 R2 and 2016 cases. An installed-version check confirmed 4.7.2 even though the components view still showed 4.6.
Should I use Rapid SCADA MQTT driver 5.3.1 RU or 5.0.4.0 RU?
Use 5.3.1 RU for a version 5 installation because it is the newer driver. Consider version 6 only after confirming that the project's required modules and driver-configuration workflow are supported.