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Write to Tag demo

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support
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09 Oct 2024 18:44 #13216 by support

Replied by support on topic Write to Tag demo

Hello.

From our point of view, this is controlled by the OPC server, and the OPC specifications do not tell *how* it is done - it can differ for each server. Some may have it fixed, some configurable, some may use access rights from a downstream system. I would ask the server vendor for more info.

There is generally no way to control the access rights through OPC programmatically.

Best regards

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tlaford
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09 Oct 2024 18:27 #13215 by tlaford

Replied by tlaford on topic Write to Tag demo

When I execute this line:

object value = client.ReadItemValue("localhost","myServer.OPC.ServerClass","MyMachine.My.Tag.Name")

It returns a string.

When I try to change that string using this code:

client.WriteItemValue("localhost","myServer.OPC.ServerClass","MyMachine.My.Tag.Name","myValue")

it throws an exception

The Items AccessRights do not allow the operation.
+ The client method called (or event/callback invoked) was 'WriteMultipleItemValues[1]'.

What controls the AccessRights? Is it controlled by the OPC server itself, by the "gateway" program that allows me to communicate from my computer to the actual machine, or is it something that can be controlled programmatically?

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