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DCOM issues in recent Windows updates


There was an issue regarding DCOM functionality in recent Windows 10 updates. As a result, certain OPC client were not able to connect to server applications made with our Sentrol SDK.

The issue

In short, the issue was experienced by OPC client applications when these applications tried to connect to OPCEnum service or certain OPC servers. For OPCEnum, the following error message was shown: Could not connect to OPCEnum service at 'localhost': Interface IOPCServerList not supported: Access is denied.

The warning message.

This message was displayed when starting the Prosys OPC Client or refreshing the server list without the ‘Registry’ option enabled.

The issue also prevented connecting to server applications made with our Sentrol SDK if the server was running as a service. In this case, the error message was: Cannot connect to OPC Server \\localhost\Prosys.OPC.Service: Interface IOPCServerList not supported: Access is denied.

The warning message.

Problem resolution

After some investigations, it became clear that this issue was introduced in certain Windows 10 updates. For the 1709 version, the breaking update is KB4056892. You can easily see if the update is installed from the Control Panel. Alternatively, you an run the Winver command and verify that the Build version shows up as 16299.192.


In Windows update history the issue is formulated as “When calling CoInitializeSecurity, the call will fail if passing RPC_C_IMP_LEVEL_NONE under certain conditions”.

For 64-bit Windows machines, the fix is introduced in update KB4058258. For Version 1703, the corresponding break version is KB4056891 and the issue is fixed in KB4057144.

As a conclusion, we recommend to install the latest Windows 10 updates, and this should fix the problem automatically

Heikki Tahvanainen

Heikki Tahvanainen

Customer Service Manager

Email: heikki.tahvanainen@prosysopc.com

Expertise and responsibility areas: Prosys OPC product and service sales and customer relationships

Tags: OPC Classic, SDK for Delphi, DCOM, Delphi

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About Prosys OPC Ltd

Prosys OPC is a leading provider of professional OPC software and services with over 20 years of experience in the field. OPC and OPC UA (Unified Architecture) are communications standards used especially by industrial and high-tech companies.

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