Hello.

I have tried versions 5.35 and 5.40, and they behave the same. Both report E_BADTYPE when writing from the demo app to Static/Simple Types/Int. But they do not report any error when writing to a String item.

Without actually looking in details of it, I think that that may be the reason: The demo application always writes a string to the item. That's why writing a string works. But the server may be rejecting a string value being written to a numeric item.

In COM-based OPC-DA, at least in its latest version, the servers are actually required to convert, with some simplification, "everything to everything", so they have to convert strings to numbers etc. I will have to check OPC-XML DA spec, but most likely it does not require the servers to do so. With servers that do not make such conversion, the demo app may only be able to write strings, therefore.

Can you try modifying the code of the demo app to convert the value to an integer first?

Regards