Hello,
thank you for letting me know, and I am glad the issue is resolved. I assume that setting the MaximumAge to 0 was what has fixed it.

If you had let me know that you have problems converting to FoxPro. I would have a workaround for you: We have ReadItemList method that does the same thing, but instead of arrays it uses a list object (and we have ElasticVector class for it).It was introduced for another language (PowerScript) which also had problem dealing with COM arrays.

Example PowerScript code with the list (for OPC DA, not OPC UA, and without the MaximumAge setting, but the principles are the same):

 

// This example shows how to read 4 items at once, and display their values, timestamps and qualities.

 

mle_outputtext.Text = ""

 

// Instantiate the client object

OLEObject client

client = CREATE OLEObject

client.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")

 

// Prepare arguments.

 

OLEObject readItemArguments1

readItemArguments1 = CREATE OLEObject

readItemArguments1.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")

readItemArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"

readItemArguments1.ItemDescriptor.ItemID = "Simulation.Random"

 

OLEObject readItemArguments2

readItemArguments2 = CREATE OLEObject

readItemArguments2.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")

readItemArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"

readItemArguments2.ItemDescriptor.ItemID = "Trends.Ramp (1 min)"

 

OLEObject readItemArguments3

readItemArguments3 = CREATE OLEObject

readItemArguments3.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")

readItemArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"

readItemArguments3.ItemDescriptor.ItemID = "Trends.Sine (1 min)"

 

OLEObject readItemArguments4

readItemArguments4 = CREATE OLEObject

readItemArguments4.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")

readItemArguments4.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"

readItemArguments4.ItemDescriptor.ItemID = "Simulation.Register_I4"

 

OLEObject readItemArgumentsList

readItemArgumentsList = CREATE OLEObject

readItemArgumentsList.ConnectToNewObject("OpcLabs.BaseLib.Collections.ElasticVector")

readItemArgumentsList.Add(readItemArguments1)

readItemArgumentsList.Add(readItemArguments2)

readItemArgumentsList.Add(readItemArguments3)

readItemArgumentsList.Add(readItemArguments4)

 

// Obtain values/timestamps/qualities.

OLEObject vtqResultList

vtqResultList = client.ReadItemList(readItemArgumentsList)

 

// Display results

Int i

FOR i = 0 TO vtqResultList.Count - 1

  OLEObject vtqResult

  vtqResult = vtqResultList.Item

  IF vtqResult.Succeeded THEN

    mle_outputtext.Text = mle_outputtext.Text + "vtqResult[" + String(i) + "].Vtq: " + String(vtqResult.Vtq) + "~r~n"

  ELSE

    mle_outputtext.Text = mle_outputtext.Text + "vtqResult[" + String(i) + "] *** Failure: " + vtqResult.ErrorMessageBrief + "~r~n"

  END IF  

NEXT

 

 

Best regards

Please read my post again. It is explained there why not.

Thank you.

There should not be much difference between what you are doing from the Prosys client, and what QuickOPC does. The only significant difference I can think of is the MaximumAge parameter for the read. Our default is 1000 milliseconds; it Prosys client might be using 0 ("read from the data source"). It would be worth trying that.

I do not have FoxPro example, but I have a VBScript which you should be able to adapt. Note that (in COM), we do not have a function that reads just single value in this way, so you will need to use the method that reads "multiple" values - even though you can shrink the number down to 1 if you like.

What matters is the assignment of zero to the .MaximumAge in the code below:

 

Rem This example shows how to read 3 values (without status or timestamps) at once, from the device (data source).

 

Option Explicit

 

' Instantiate the client object

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient")

 

Dim ReadArguments1: Set ReadArguments1 = CreateObject("OpcLabs.EasyOpc.UA.OperationModel.UAReadArguments")

ReadArguments1.EndpointDescriptor.UrlString = "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"

ReadArguments1.NodeDescriptor.NodeId.ExpandedText = "nsu=http://test.org/UA/Data/ ;i=10845"

ReadArguments1.ReadParameters.MaximumAge = 0.0

 

Dim ReadArguments2: Set ReadArguments2 = CreateObject("OpcLabs.EasyOpc.UA.OperationModel.UAReadArguments")

ReadArguments2.EndpointDescriptor.UrlString = "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"

ReadArguments2.NodeDescriptor.NodeId.ExpandedText = "nsu=http://test.org/UA/Data/ ;i=10853"

ReadArguments2.ReadParameters.MaximumAge = 0.0

 

Dim ReadArguments3: Set ReadArguments3 = CreateObject("OpcLabs.EasyOpc.UA.OperationModel.UAReadArguments")

ReadArguments3.EndpointDescriptor.UrlString = "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"

ReadArguments3.NodeDescriptor.NodeId.ExpandedText = "nsu=http://test.org/UA/Data/ ;i=10855"

ReadArguments3.ReadParameters.MaximumAge = 0.0

 

Dim arguments(2)

Set arguments(0) = ReadArguments1

Set arguments(1) = ReadArguments2

Set arguments(2) = ReadArguments3

 

' Obtain values. By default, the Value attributes of the nodes will be read.

Dim results: results = Client.ReadMultipleValues(arguments)

 

' Display results

Dim i: For i = LBound(results) To UBound(results)

  Dim ValueResult: Set ValueResult = results(i)

  If ValueResult.Succeeded Then

    WScript.Echo "Value: " & ValueResult.Value

  Else

    WScript.Echo "*** Failure: " & ValueResult.ErrorMessageBrief

  End If

Next

 

' Example output:

'

'Value: 8

'Value: -8.06803E+21

'Value: Strawberry Pig Banana Snake Mango Purple Grape Monkey Purple? Blueberry Lemon^      



 

If this does not help, we may have to resort to Wireshark analysis of the communication.

Best regards

Hello,
do you mean the "Prosys OPC UA Browser" client? (if not, and you are using something else, please point me to the precise location/information).

If you are using Prosys OPC UA Browser: Do you simply look at the value of the Value attribute after selecting the node from the tree, OR are you doing "Monitor Data" and then watching the value changes in the "Data View" tab?

Regards

Hello.
No, there should be no need to "refresh" the value.

I have some additional questions:

1)I do not quite understand how the following two statements fit together:
- "the value of tag doesn't change when I read with my program...."
- "If I write the same tag the value is written correctly and I read it without problems."
Are you saying that the difference is that in the first case, the values is changed "from within" the server?

2) Which OPC UA server are you connecting to?

3) You talk about "reads" - please just confirm that you are *not* using subscriptions (in this case).

Best regards