The reliance on opcnetapidll and DCOM is one of the biggest pain points in industrial automation. DCOM is notoriously difficult to configure across firewalls and domains. This is why the industry is shifting to OPC UA (Unified Architecture) .
The library supports both methods of communication:
As a last resort:
You may encounter these errors:
| Error Message | Typical Cause |
|---------------|----------------|
| "opcnetapidll not found" | Missing file, deleted by antivirus, or corrupted installation |
| "The procedure entry point could not be located in opcnetapidll" | Version mismatch – the calling app expects a different function export |
| "Access violation in opcnetapidll" | Memory corruption, incompatible .NET runtime, or hardware issue |
| "Failed to load opcnetapidll. The specified module could not be found." | Missing dependencies (e.g., Visual C++ Redistributables, .NET Framework) |
| "opcnetapidll is either not designed to run on Windows or it contains an error" | 32-bit vs 64-bit mismatch, or the file is corrupt |
If you are reading this article, you are likely troubleshooting an error. Here are the most common error messages involving opcnetapidll:
You will typically find this file in the installation directories of:
Legacy COM-based OPC servers might need manual registration:
Modern .NET OPC assemblies are usually not registered via regsvr32 – they are loaded directly by .NET applications.