The project is public and MIT so anyone who has the job maintaining old systems can share fixes and the OPC-F will review them and provide updated signed installers if they are deemed necessary.

This should be sufficient to support the community as long as needed.

As many of you may have seen, the OPC Foundation has officially declared the OPC Core Components (OPC Classic / OPC DA) as strictly legacy, entirely unmaintained, and at its final End-of-Life (EOL) under the OPC MIT license.

For systems relying on older field devices, third-party integration servers, and legacy hardware, OPC Classic remains a reality of day-to-day operations. However, depending on an unmaintained codebase—especially one tied to legacy DCOM and critical Windows components—presents growing maintenance and security challenges.

While migrating entirely to OPC UA is the ultimate long-term goal, we recognize that replacing legacy field controllers overnight isn't always feasible for every site.

What is your reccomendation to support ongoing operations safely?

Looking forward to your insights and real-world experiences.

https://opcfoundation.org/deve.....urce-code/

I am not aware anything available today.

I am working on a project that requires me to implement an OPC Xi server to maintain compatibility with a legacy client.

I have been searching for the original OPC Xi Reference Implementation, SDK, or Compliance Test Tool binaries, but as these were deprecated years ago, I am unable to find any functional links or repositories.

Does anyone happen to have an archive of these legacy OPC Foundation OPC Xi resources (circa 2010–2012)? Even if the code is outdated, having the reference implementation would be incredibly helpful for debugging my current attempt at a server implementation.

Any leads or pointers on how to actually target this standard would be greatly appreciated.

Thank you for your time and help.

The download includes a powershell script that will clean up a 3.1.1 installation that was corrupted by the duplicate component ids.

Disclaimer: This is my product. You can contact me at sales09 (at) opclabs.com for questions.

Best regards

You can look at vendors that offer their own .NET libraries for COM access.

During development, we got a windows virtual machine that runs the OPC DA server. Using OPC Expert, we can already see the server and read variable changes. 

So far so good, but how can we implement a client that can read the data?

What we tried so far: 

a) python 32bit with pywin32 and OpenOPC

b) Native .net 8 

Both won't work because the automation layer (opcdaauto.dll from OPC Foundation) is not present.

What is the official way to develop a client, and from where do we get the opcdaauto.dll since it is not bundled in the redistributable package download?

Thanks in advance!

Are you available to verify before it is posted?

The installer has encountered an unexpected error installing this package. This may indicate a problem with this package. The error code is 2753. The arguments are: file_OpcEnum.E25DF0F2_0F29_47E8_8537_265285ED9757, ,

Error code 2753 is "The File '[2]' is not marked for installation."

There is a similar issue with UnregisterOpcEnum.E25DF0F2_0F29_47E8_8537_265285ED9757 action which doesn't handle uninstalling an optional feature that includes the merge module without uninstalling the whole application.

A possible fix is to change the register condition to: $comp_OpcEnum.E25DF0F2_0F29_47E8_8537_265285ED9757 = 3

and the unregister condition to: $comp_OpcEnum.E25DF0F2_0F29_47E8_8537_265285ED9757 = 2

which takes into account the action being performed to the OpcEnum component.

The same problem exists in the "opc-com-proxystub-mergemodule-3.1.1-x64.msm" merge module with the RegisterOpcCategoryManager.E68AB89F_6DF7_4750_8BC1_F14B2064F313 and UnregisterOpcCategoryManager.E68AB89F_6DF7_4750_8BC1_F14B2064F313 actions.

Fix for register condition: $comp_OpcCategoryManager.E68AB89F_6DF7_4750_8BC1_F14B2064F313 = 3

Fix for unregister condition: $comp_OpcCategoryManager.E68AB89F_6DF7_4750_8BC1_F14B2064F313 = 2

Specifically the component GUID's in "opc-com-proxystub-mergemodule-3.1.1-x86.msm" and "opc-com-proxystub-mergemodule-3.1.1-x64.msm" are the same. Similarly, the GUIDs in "opc-com-sdk-mergemodule-3.1.1-x86.msm" and "opc-com-sdk-mergemodule-3.1.1-x64.msm" are also the same.

This issue can be seen by validating "opc-core-components-redistributable-3.1.1-x64.msi" using Microsoft Orca (see https://learn.microsoft.com/en.....i/orca-exe). It also occurs in any product that includes both x86 and x64 merge modules in it's MSI file.

ICE08 ERROR Component: comp_opcsec_ps.E68AB89F_6DF7_4750_8BC1_F14B2064F313 has a duplicate GUID: {A1B2C3D4-0008-4000-8000-000000000008}
ICE08 ERROR Component: comp_opchda_ps.E68AB89F_6DF7_4750_8BC1_F14B2064F313 has a duplicate GUID: {A1B2C3D4-0007-4000-8000-000000000007}
ICE08 ERROR Component: comp_OpcDxPs.E68AB89F_6DF7_4750_8BC1_F14B2064F313 has a duplicate GUID: {A1B2C3D4-0006-4000-8000-000000000006}
ICE08 ERROR Component: comp_OpcCmdPs.E68AB89F_6DF7_4750_8BC1_F14B2064F313 has a duplicate GUID: {A1B2C3D4-0005-4000-8000-000000000005}
ICE08 ERROR Component: comp_opcbc_ps.E68AB89F_6DF7_4750_8BC1_F14B2064F313 has a duplicate GUID: {A1B2C3D4-0004-4000-8000-000000000004}
ICE08 ERROR Component: comp_opc_aeps.E68AB89F_6DF7_4750_8BC1_F14B2064F313 has a duplicate GUID: {A1B2C3D4-0003-4000-8000-000000000003}
ICE08 ERROR Component: comp_opcproxy.E68AB89F_6DF7_4750_8BC1_F14B2064F313 has a duplicate GUID: {A1B2C3D4-0002-4000-8000-000000000002}
ICE08 ERROR Component: comp_opccomn_ps.E68AB89F_6DF7_4750_8BC1_F14B2064F313 has a duplicate GUID: {A1B2C3D4-0001-4000-8000-000000000001}

ICE08 ERROR Component: sdk_OpcDxError_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-001A-4000-9000-00000000001A}
ICE08 ERROR Component: sdk_OpcDx_idl.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0019-4000-9000-000000000019}
ICE08 ERROR Component: sdk_OpcDx_i.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0018-4000-9000-000000000018}
ICE08 ERROR Component: sdk_OpcDx_h.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0017-4000-9000-000000000017}
ICE08 ERROR Component: sdk_OpcCmdError_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0016-4000-9000-000000000016}
ICE08 ERROR Component: sdk_OpcCmd_idl.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0015-4000-9000-000000000015}
ICE08 ERROR Component: sdk_OpcCmd_i.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0014-4000-9000-000000000014}
ICE08 ERROR Component: sdk_OpcCmd_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0013-4000-9000-000000000013}
ICE08 ERROR Component: sdk_OpcBatchDef_h.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0012-4000-9000-000000000012}
ICE08 ERROR Component: sdk_OpcBatchProps_h.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0011-4000-9000-000000000011}
ICE08 ERROR Component: sdk_OpcBatchError_h.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0010-4000-9000-000000000010}
ICE08 ERROR Component: sdk_opcbc_idl.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-000F-4000-9000-00000000000F}
ICE08 ERROR Component: sdk_OpcCmdPs_dll.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0034-4000-9000-000000000034}
ICE08 ERROR Component: sdk_opcsec_ps_dll.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0037-4000-9000-000000000037}
ICE08 ERROR Component: sdk_opchda_ps_dll.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0036-4000-9000-000000000036}
ICE08 ERROR Component: sdk_opcbc_ps_dll.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0033-4000-9000-000000000033}
ICE08 ERROR Component: sdk_OpcDxPs_dll.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0035-4000-9000-000000000035}
ICE08 ERROR Component: sdk_opchda_i.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-001C-4000-9000-00000000001C}
ICE08 ERROR Component: sdk_opc_aeps_dll.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0032-4000-9000-000000000032}
ICE08 ERROR Component: sdk_opcproxy_dll.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0031-4000-9000-000000000031}
ICE08 ERROR Component: sdk_opccomn_ps_dll.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0030-4000-9000-000000000030}
ICE08 ERROR Component: sdk_OpcErrSec_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0022-4000-9000-000000000022}
ICE08 ERROR Component: sdk_opcSec_idl.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0021-4000-9000-000000000021}
ICE08 ERROR Component: sdk_opcSec_h.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-001F-4000-9000-00000000001F}
ICE08 ERROR Component: sdk_opcSec_i.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0020-4000-9000-000000000020}
ICE08 ERROR Component: sdk_OpcHda_Error_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-001E-4000-9000-00000000001E}
ICE08 ERROR Component: sdk_opchda_idl.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-001D-4000-9000-00000000001D}
ICE08 ERROR Component: sdk_opchda_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-001B-4000-9000-00000000001B}
ICE08 ERROR Component: sdk_opcbc_i.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-000E-4000-9000-00000000000E}
ICE08 ERROR Component: sdk_opcbc_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-000D-4000-9000-00000000000D}
ICE08 ERROR Component: sdk_opcaedef_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-000C-4000-9000-00000000000C}
ICE08 ERROR Component: sdk_opcae_er_h.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-000B-4000-9000-00000000000B}
ICE08 ERROR Component: sdk_opc_ae_idl.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-000A-4000-9000-00000000000A}
ICE08 ERROR Component: sdk_opc_ae_i.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0009-4000-9000-000000000009}
ICE08 ERROR Component: sdk_opc_ae_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0008-4000-9000-000000000008}
ICE08 ERROR Component: sdk_opcerror_h.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0007-4000-9000-000000000007}
ICE08 ERROR Component: sdk_opcda_idl.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0006-4000-9000-000000000006}
ICE08 ERROR Component: sdk_opcda_i.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0005-4000-9000-000000000005}
ICE08 ERROR Component: sdk_opcda_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0004-4000-9000-000000000004}
ICE08 ERROR Component: sdk_opccomn_idl.E68AB8A0_6DF7_4750_8BC1_F14B2064F314 has a duplicate GUID: {B2C3D4E5-0003-4000-9000-000000000003}
ICE08 ERROR Component: sdk_opccomn_i.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0002-4000-9000-000000000002}
ICE08 ERROR Component: sdk_opccomn_h.E25DF0F3_0F29_47E8_8537_265285ED9758 has a duplicate GUID: {B2C3D4E5-0001-4000-9000-000000000001}

These GUID appear to have been created 'manually' rather the usual algorithmically generated unique GUID's.