In This Topic

Introduction

OPC Unified Architecture has support for single- and multidimensional arrays in data values. In addition, it is also possible to work with (read, write, subscribe to) only a subset of an array, so that the whole (potentially large) array does not have to be transferred between the OPC server and OPC client.

QuickOPC-UA uses Index Range Lists (UAIndexRangeList objects) to control which parts of array value should be accessed. An index range list can be used to identify the whole array, a single element of a structure or an array, or a single range of indexes for arrays. Index Range List is basically a list of individual Index Ranges (UAIndexRange objects), each containing a range for a single dimension of an array.

There is an implicit conversion from an integer (Int32) to a UAIndexRange, so if your language (such as C#) supports implicit conversions, an index range containing just a single element can be written simply as the element index, without explicitly constructing the UAIndexRange object.

Besides constructing the UAIndexRangeList from individual UAIndexRange objects, it is also possible to specify the index range list by parsing a string, using static UAIndexRangeList.TryParse method.

Examples of index range strings:

5:20
10:11,1:2
1,4:7,90

Dimensions are separated by commas. A minimum and maximum value, separated by a colon, denotes a range of index. If the colon is missing, only a single for an index is selected. An empty string denotes the whole array.

One-dimensional index range lists can be easily constructed using the UAIndexRangeList.OneDimension static method, passing it either the single index, or minimum and maximum indices.

UAIndexRangeList can be given as IndexRangeList property of the UAAttributeArguments object (and derived objects, such as UAReadArguments, UAWriteArguments, UAWriteValueArguments, and EasyUAMonitoredItemArguments). You can then pass this object to a corresponding method on the main EasyUAClient object.

Examples

.NET

// This example shows how to read a range of values from an array.

using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._UAIndexRangeList
{
    partial class Usage
    {
        public static void ReadValue()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            // Instantiate the client object
            var client = new EasyUAClient();

            // Obtain the value, indicating that just the elements 2 to 4 should be returned
            object value;
            try
            {
                value = client.ReadValue(
                    new UAReadArguments(
                        endpointDescriptor,
                        "nsu=http://test.org/UA/Data/ ;ns=2;i=10305",   // /Data.Static.Array.Int32Value
                        UAIndexRangeList.OneDimension(2, 4)));
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            // Cast to typed array
            var arrayValue = (Int32[]) value;

            // Display results
            for (int i = 0; i < 3; i++)
                Console.WriteLine("arrayValue[{0}]: {1}", i, arrayValue[i]);


            // Example output:
            //arrayValue[0]: 180410224
            //arrayValue[1]: 1919239969
            //arrayValue[2]: 1700185172
        }
    }
}

# This example shows how to read a range of values from an array.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.OperationModel import *


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object.
client = EasyUAClient()

# Obtain the value, indicating that just the elements 2 to 4 should be returned
try:
    arrayValue = IEasyUAClientExtension.ReadValue(client,
                                                  endpointDescriptor,
                                                  UANodeDescriptor('nsu=http://test.org/UA/Data/ ;ns=2;i=10305'),    # /Data.Static.Array.Int32Value
                                                  UAIndexRangeList.OneDimension(2, 4))
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# Display results.
for i, elementValue in enumerate(arrayValue):
    print('arrayValue[', i, ']: ', elementValue, sep='')

print()
print('Finished.')

' This example shows how to read a range of values from an array.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _UAIndexRangeList
    Friend Class Usage
        Public Shared Sub ReadValue()

            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object
            Dim client = New EasyUAClient()

            ' Obtain the value, indicating that just the elements 2 to 4 should be returned
            Dim value As Object
            Try
                value = client.ReadValue( _
                    New UAReadArguments( _
                        endpointDescriptor, _
                        "nsu=http://test.org/UA/Data/ ;i=10305", _
                        UAIndexRangeList.OneDimension(2, 4)))
                ' or "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' Cast to typed array
            Dim arrayValue = DirectCast(value, Int32())

            ' Display results
            For i = 0 To 2
                Console.WriteLine("arrayValue[{0}]: {1}", i, arrayValue(i))
            Next
        End Sub
    End Class
End Namespace

COM

// This example shows how to read a range of values from an array.

class procedure Usage.ReadValue;
var
  Client: _EasyUAClient;
  EndpointDescriptor: string;
  ReadArguments1: _UAReadArguments;
  Arguments, Results: OleVariant;
  I: Cardinal;
  IndexRange: _UAIndexRange;
  IndexRangeList: OpcLabs_EasyOpcUA_TLB._UAIndexRangeList;
  ArrayValue: OleVariant;
  Value: Integer;
  ValueResult: _ValueResult;
begin
  EndpointDescriptor := 
    //'http://opcua.demo-this.com:51211/UA/SampleServer';
    //'https://opcua.demo-this.com:51212/UA/SampleServer/';
    'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer';

  // Instantiate the client object
  Client := CoEasyUAClient.Create;

  // Prepare the arguments, indicating that just the elements 2 to 4 should be returned.
  IndexRangeList := CoUAIndexRangeList.Create;
  IndexRange := CoUAIndexRange.Create;
  IndexRange.Minimum := 2;
  IndexRange.Maximum := 4;
  IndexRangeList.Add(IndexRange);

  ReadArguments1 := CoUAReadArguments.Create;
  ReadArguments1.EndpointDescriptor.UrlString := EndpointDescriptor;
  ReadArguments1.NodeDescriptor.NodeId.ExpandedText := 'nsu=http://test.org/UA/Data/ ;ns=2;i=10305';
  ReadArguments1.IndexRangeList := IndexRangeList;

  Arguments := VarArrayCreate([0, 0], varVariant);
  Arguments[0] := ReadArguments1;

  // Obtain value.
  TVarData(Results).VType := varArray or varVariant;
  TVarData(Results).VArray := PVarArray(Client.ReadMultipleValues(Arguments));

  ValueResult := IInterface(Results[0]) as _ValueResult;
  if not ValueResult.Succeeded then
    begin
      WriteLn(' *** Failure: ', ValueResult.Exception.GetBaseException.Message);
      Exit;
    end;

  // Display results
  ArrayValue := ValueResult.Value;
  for I := VarArrayLowBound(ArrayValue, 1) to VarArrayHighBound(ArrayValue, 1) do
  begin
      Value := ArrayValue[I];
      WriteLn('arrayValue[', I, ']: ', Value);
  end;

  VarClear(Results);
  VarClear(Arguments);

  // Example output:
  //arrayValue[0]: 180410224
  //arrayValue[1]: 1919239969
  //arrayValue[2]: 1700185172
end;

// This example shows how to read a range of values from an array.

$EndpointDescriptor = 
    //"http://opcua.demo-this.com:51211/UA/SampleServer";
    //"https://opcua.demo-this.com:51212/UA/SampleServer/";
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";

// Instantiate the client object
$Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient");

// Prepare the arguments, indicating that just the elements 2 to 4 should be returned.
$IndexRangeList = new COM("OpcLabs.EasyOpc.UA.UAIndexRangeList");
$IndexRange = new COM("OpcLabs.EasyOpc.UA.UAIndexRange");
$IndexRange->Minimum = 2;
$IndexRange->Maximum = 4;
$IndexRangeList->Add($IndexRange);

$ReadArguments1 = new COM("OpcLabs.EasyOpc.UA.OperationModel.UAReadArguments");
$ReadArguments1->EndpointDescriptor->UrlString = $EndpointDescriptor;
$ReadArguments1->NodeDescriptor->NodeId->ExpandedText = "nsu=http://test.org/UA/Data/ ;ns=2;i=10305";
$ReadArguments1->IndexRangeList = $IndexRangeList;

$arguments[0] = $ReadArguments1;

// Obtain value.
$results = $Client->ReadMultipleValues($arguments);

$ValueResult = $results[0];

if (!$ValueResult->Succeeded) {
    printf("*** Failure: %s\n", $ValueResult->ErrorMessageBrief);
    Exit();
}

// Display results
$ArrayValue = $ValueResult->Value;
for ($i = 0; $i <= 2; $i++)
{
    printf("arrayValue[d]s\n", $i, $ArrayValue[$i]);
}

// Example output:
//arrayValue[0]: 180410224
//arrayValue[1]: 1919239969
//arrayValue[2]: 1700185172

Rem This example shows how to read a range of values from an array.

Private Sub Usage_ReadValue_Command_Click()
    OutputText = ""
    
    Dim endpointDescriptor As String
    'endpointDescriptor = "http://opcua.demo-this.com:51211/UA/SampleServer"
    'endpointDescriptor = "https://opcua.demo-this.com:51212/UA/SampleServer/"
    endpointDescriptor = "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"

    ' Instantiate the client object
    Dim Client As New EasyUAClient

    ' Prepare the arguments, indicating that just the elements 2 to 4 should be returned.
    Dim indexRangeList As New UAIndexRangeList
    Dim indexRange As New UAIndexRange
    indexRange.Minimum = 2
    indexRange.Maximum = 4
    indexRangeList.Add indexRange
    
    Dim readArguments1 As New UAReadArguments
    readArguments1.endpointDescriptor.UrlString = endpointDescriptor
    readArguments1.NodeDescriptor.NodeId.expandedText = "nsu=http://test.org/UA/Data/ ;ns=2;i=10305"
    Set readArguments1.indexRangeList = indexRangeList

    Dim arguments(0) As Variant
    Set arguments(0) = readArguments1

    ' Obtain value.
    Dim results() As Variant
    results = Client.ReadMultipleValues(arguments)

    Dim valueResult As valueResult
    Set valueResult = results(0)
    If Not valueResult.Succeeded Then
        OutputText = OutputText & "*** Failure: " & valueResult.Exception.GetBaseException.Message & vbCrLf
        Exit Sub
    End If
    
    ' Display results
    Dim arrayValue() As Long
    arrayValue = valueResult.value
    
    Dim i: For i = LBound(arrayValue) To UBound(arrayValue)
        OutputText = OutputText & "arrayValue(" & i & "):" & arrayValue(i) & vbCrLf
    Next

    ' Example output:
    'arrayValue(0): 180410224
    'arrayValue(1): 1919239969
    'arrayValue(2): 1700185172
End Sub

Rem This example shows how to read a range of values from an array.

Option Explicit

Dim endpointDescriptor: endpointDescriptor = _
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
    '"http://opcua.demo-this.com:51211/UA/SampleServer"  
    '"https://opcua.demo-this.com:51212/UA/SampleServer/"

' Instantiate the client object
Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient")

' Prepare the arguments, indicating that just the elements 2 to 4 should be returned.
Dim IndexRangeList: Set IndexRangeList = CreateObject("OpcLabs.EasyOpc.UA.UAIndexRangeList")
Dim IndexRange: Set IndexRange = CreateObject("OpcLabs.EasyOpc.UA.UAIndexRange")
IndexRange.Minimum = 2
IndexRange.Maximum = 4
IndexRangeList.Add IndexRange
'
Dim ReadArguments1: Set ReadArguments1 = CreateObject("OpcLabs.EasyOpc.UA.OperationModel.UAReadArguments")
ReadArguments1.EndpointDescriptor.UrlString = endpointDescriptor
ReadArguments1.NodeDescriptor.NodeId.ExpandedText = "nsu=http://test.org/UA/Data/ ;ns=2;i=10305"
ReadArguments1.IndexRangeList = IndexRangeList

Dim arguments(0)
Set arguments(0) = ReadArguments1

' Obtain the value.
Dim results: results = Client.ReadMultipleValues(arguments)
Dim ValueResult: Set ValueResult = results(0)
If Not ValueResult.Succeeded Then
    WScript.Echo "*** Failure: " & ValueResult.Exception.GetBaseException().Message
    WScript.Quit
End If
' VBScript can only handle well arrays of VARIANTs; most other COM tool will be able to use simply the .Value property.
Dim arrayValue: arrayValue = ValueResult.RegularizedValue

' Display results
Dim i: For i = 0 To 2
    WScript.Echo "arrayValue[" & i & "]: " & arrayValue(i)
Next


' Example output:
'arrayValue[0]: 180410224
'arrayValue[1]: 1919239969
'arrayValue[2]: 1700185172

C#
Python (.NET)

// This example shows how to subscribe to range of values from an array.

using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._UAIndexRangeList
{
    partial class Usage
    {
        public static void Subscribe()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            // Instantiate the client object
            var client = new EasyUAClient();

            Console.WriteLine("Subscribing to range...");
            var attributeArguments = new UAAttributeArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10933")
                {
                    IndexRangeList = UAIndexRangeList.OneDimension(2, 4)
                };
            var monitoredItemArguments = new UAMonitoredItemArguments(attributeArguments, monitoringParameters:1000);
            // The callback is a lambda expression the displays the value
            client.SubscribeMonitoredItem(monitoredItemArguments,
                (sender, eventArgs) =>
                {
                    if (eventArgs.Succeeded)
                    {
                        var arrayValue = eventArgs.AttributeData.Value as Int32[];
                        if (!(arrayValue is null))
                            Console.WriteLine($"Value: {{{String.Join(",", arrayValue)}}}");
                    }
                    else
                        Console.WriteLine($"*** Failure: {eventArgs.ErrorMessageBrief}");
                });

            Console.WriteLine("Processing data change events for 10 seconds...");
            System.Threading.Thread.Sleep(10 * 1000);

            Console.WriteLine("Unsubscribing...");
            client.UnsubscribeAllMonitoredItems();

            Console.WriteLine("Waiting for 2 seconds...");
            System.Threading.Thread.Sleep(2 * 1000);
        }
    }
}

# This example shows how to subscribe to range of values from an array.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc
import time

# Import .NET namespaces.
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.OperationModel import *


def dataChangeNotification(sender, eventArgs):
    # Display value.
    if eventArgs.Succeeded:
        arrayValue = eventArgs.AttributeData.Value
        print('Value: {', ", ".join(["{}"]*len(arrayValue)).format(*arrayValue), '}', sep='')
    else:
        print('*** Failure: ', eventArgs.ErrorMessageBrief, sep='')


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object.
client = EasyUAClient()

print('Subscribing to range...')
attributeArguments = UAAttributeArguments(endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10933'))
attributeArguments.IndexRangeList = UAIndexRangeList.OneDimension(2, 4)
monitoredItemArguments = UAMonitoredItemArguments(attributeArguments, UAMonitoringParameters(1000))
IEasyUAClientExtension.SubscribeMonitoredItem(client,
    monitoredItemArguments,
    EasyUADataChangeNotificationEventHandler(dataChangeNotification))

print('Processing data change events for 10 seconds...')
time.sleep(10)

print('Unsubscribing...')
client.UnsubscribeAllMonitoredItems()

print('Waiting for 2 seconds...')
time.sleep(2)

print('Finished.')

Examples - OPC Unified Architecture

Examples - OPC Unified Architecture - Read a range of elements from an array

Examples - OPC Unified Architecture - Subscribe to a range of elements from an array