PullDataChangeNotification Method (

Attempts to pull an OPC data change notification subscribed to by the OpcLabs.EasyOpc.UA.IEasyUAClient.SubscribeMultipleMonitoredItems or SubscribeDataChange method.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<CanBeNullAttribute()>
Function PullDataChangeNotification( _
   ByVal millisecondsTimeout As Integer _
) As EasyUADataChangeNotificationEventArgs

'Usage
 
Dim instance As _EasyUAClient
Dim millisecondsTimeout As Integer
Dim value As EasyUADataChangeNotificationEventArgs
 
value = instance.PullDataChangeNotification(millisecondsTimeout)

[CanBeNull()]
EasyUADataChangeNotificationEventArgs PullDataChangeNotification( 
   int millisecondsTimeout
)

[CanBeNull()]
EasyUADataChangeNotificationEventArgs^ PullDataChangeNotification( 
   int millisecondsTimeout
)

Parameters

millisecondsTimeout: The number of milliseconds to wait, or System.Threading.Timeout.Infinite (-1) to wait indefinitely.
Valid values of this parameter are in the range from -1 to 2147483647 (Int32.MaxValue).

Return Value

The event arguments, or null if no event is available within the specified time.

This method can return null (Nothing in Visual Basic).

Exceptions

Exception Description

Exception	Description
System.ArgumentNullException	A `null` reference (`Nothing` in Visual Basic) is passed to a method that does not accept it as a valid argument. This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.
System.ArgumentOutOfRangeException	The value of an argument is outside the allowable range of values as defined by the invoked method. This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

System.ArgumentNullException

A null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.

This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

System.ArgumentOutOfRangeException

The value of an argument is outside the allowable range of values as defined by the invoked method.

This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

Remarks

This member or type is for use from COM. It is not meant to be used from .NET or Python. Refer to the corresponding .NET member or type instead, if you are developing in .NET or Python.

This is an extension method (info: C#, VB.NET). In languages that have support for extensions methods (such as C# and VB.NET), you can use the extension method as if it were a regular method on the object that is its first parameter. In other languages (such as with Python.NET), you will call the extension as a static method, and pass it the object on which it acts as its first parameter.

Example

// This example shows how to subscribe to changes of a single monitored item, pull events, and display each change.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

var Client = new ActiveXObject("OpcLabs.EasyOpc.UA.EasyUAClient");
// In order to use event pull, you must set a non-zero queue capacity upfront.
Client.PullDataChangeNotificationQueueCapacity = 1000;

WScript.Echo("Subscribing...");
Client.SubscribeDataChange(
    //"http://opcua.demo-this.com:51211/UA/SampleServer",
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer",
    "nsu=http://test.org/UA/Data/ ;i=10853", 1000);

WScript.Echo("Processing data change events for 1 minute...");
var endTime = new Date().getTime() + 60*1000
do {
    var EventArgs = Client.PullDataChangeNotification(2*1000);
    if (EventArgs !== null) {
        //  Handle the notification event
        WScript.Echo(EventArgs);
    }
} while(new Date().getTime() < endTime);

// This example shows how to subscribe to changes of a single monitored item, pull events, and display each change.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

class procedure PullDataChangeNotification.Main;
var
  Client: EasyUAClient;
  EndTick: Cardinal;
  EventArgs: _EasyUADataChangeNotificationEventArgs;
begin
  // Instantiate the client object
  Client := CoEasyUAClient.Create;
  // In order to use event pull, you must set a non-zero queue capacity upfront.
  Client.PullDataChangeNotificationQueueCapacity := 1000;

  WriteLn('Subscribing...');
  Client.SubscribeDataChange(
    //'http://opcua.demo-this.com:51211/UA/SampleServer',
    'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer',
    'nsu=http://test.org/UA/Data/ ;i=10853',
    1000);

  WriteLn('Processing data change events for 1 minute...');
  EndTick := GetTickCount + 60*1000;
  while GetTickCount < EndTick do
  begin
    EventArgs := Client.PullDataChangeNotification(2*1000);
    if EventArgs <> nil then
      // Handle the notification event
      WriteLn(EventArgs.ToString);
  end;

  WriteLn('Unsubscribing...');
  Client.UnsubscribeAllMonitoredItems;

  WriteLn('Finished.');
end;

// This example shows how to subscribe to changes of a single monitored item, pull events, and display each change.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in Object Pascal (Delphi) on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-OP .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

class procedure PullDataChangeNotification.Main;
var
  Client: OpcLabs_EasyOpcUA_TLB._EasyUAClient;
  EndTick: Cardinal;
  EventArgs: _EasyUADataChangeNotificationEventArgs;
begin
  // Instantiate the client object
  Client := CoEasyUAClient.Create;
  // In order to use event pull, you must set a non-zero queue capacity upfront.
  Client.PullDataChangeNotificationQueueCapacity := 1000;

  WriteLn('Subscribing...');
  Client.SubscribeDataChange(
      //'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',
    'nsu=http://test.org/UA/Data/ ;i=10853',
    1000);

  WriteLn('Processing data change events for 1 minute...');
  EndTick := Ticks + 60*1000;
  while Ticks < EndTick do
  begin
    EventArgs := Client.PullDataChangeNotification(2*1000);
    if EventArgs <> nil then
      // Handle the notification event
      WriteLn(EventArgs.ToString);
  end;

  WriteLn('Unsubscribing...');
  Client.UnsubscribeAllMonitoredItems;

  WriteLn('Finished.');
end;

// This example shows how to subscribe to changes of a single monitored item, pull events, and display each change.

mle_outputtext.Text = ""

// Instantiate the client object
OLEObject client
client = CREATE OLEObject
client.ConnectToNewObject("OpcLabs.EasyOpc.UA.EasyUAClient")
// In order to use event pull, you must set a non-zero queue capacity upfront.
client.PullDataChangeNotificationQueueCapacity = 1000

mle_outputtext.Text = mle_outputtext.Text + "Subscribing data changes..." + "~r~n"
client.SubscribeDataChange("http://opcua.demo-this.com:51211/UA/SampleServer", "nsu=http://test.org/UA/Data/ ;i=10853", 1000)

mle_outputtext.Text = mle_outputtext.Text + "Processing data change events for 1 minute..." + "~r~n"

Time endTime = RelativeTime(Now(), 60)
DO
    OLEObject eventArgs
    eventArgs = client.PullDataChangeNotification(2*1000)
    IF NOT IsNull(eventArgs) THEN
        // Handle the notification event
        mle_outputtext.Text = mle_outputtext.Text + eventArgs.DisplayString + "~r~n"
    END IF
LOOP WHILE Now() < endTime

mle_outputtext.Text = mle_outputtext.Text + "~r~n" 
mle_outputtext.Text = mle_outputtext.Text + "Finished." + "~r~n"

REM This example shows how to subscribe to changes of a single monitored item, pull events, and display each change.
REM
REM Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
REM OPC client and subscriber examples in Visual Basic on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VB .
REM Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
REM a commercial license in order to use Online Forums, and we reply to every post.

Public Sub PullDataChangeNotification_Main_Command_Click()
    OutputText = ""
    
    Dim eventArgs As EasyUADataChangeNotificationEventArgs
    
    ' Instantiate the client object
    Dim Client As New EasyUAClient
    
    ' In order to use event pull, you must set a non-zero queue capacity upfront.
    Client.PullDataChangeNotificationQueueCapacity = 1000
    
    OutputText = OutputText & "Subscribing..." & vbCrLf
    Call Client.SubscribeDataChange("opc.tcp://opcua.demo-this.com:51210/UA/SampleServer", "nsu=http://test.org/UA/Data/ ;i=10853", 1000)

    OutputText = OutputText & "Processing data changed notification events for 1 minute..." & vbCrLf
    
    Dim EndTick As Long
    EndTick = GetTickCount + 60000
    While GetTickCount < EndTick
        Set eventArgs = Client.PullDataChangeNotification(2 * 1000)
        If Not eventArgs Is Nothing Then
            ' Handle the notification event
            OutputText = OutputText & eventArgs & vbCrLf
        End If
    Wend
    
    OutputText = OutputText & "Unsubscribing..." & vbCrLf
    Client.UnsubscribeAllMonitoredItems

    OutputText = OutputText & "Finished." & vbCrLf
End Sub

Rem This example shows how to subscribe to changes of a single monitored item, pull events, and display each change.
Rem
Rem Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
Rem OPC client and subscriber examples in VBScript on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBScript .
Rem Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
Rem a commercial license in order to use Online Forums, and we reply to every post.

Option Explicit

' Instantiate the client object
Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient")
' In order to use event pull, you must set a non-zero queue capacity upfront.
Client.PullDataChangeNotificationQueueCapacity = 1000

WScript.Echo "Subscribing..."
Client.SubscribeDataChange "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer", "nsu=http://test.org/UA/Data/ ;i=10853", 1000

WScript.Echo "Processing data change events for 1 minute..."
Dim endTime: endTime = Now() + 60*(1/24/60/60)
Do
    Dim EventArgs: Set EventArgs = Client.PullDataChangeNotification(2*1000)
    If Not (EventArgs Is Nothing) Then
        ' Handle the notification event
        WScript.Echo EventArgs
    End If    
Loop While Now() < endTime

// This example shows how to subscribe to changes of a single monitored item, pull events, and display each change.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in PHP on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PHP .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

$Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient");
// In order to use event pull, you must set a non-zero queue capacity upfront.
$Client->PullDataChangeNotificationQueueCapacity = 1000;

print "Subscribing...\n";
$Client->SubscribeDataChange(
    //"http://opcua.demo-this.com:51211/UA/SampleServer", 
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer", 
    "nsu=http://test.org/UA/Data/ ;i=10853", 
    1000);

print "Processing data change events for 1 minute...\n";
$endTime = time() + 60;
do {
    $EventArgs = $Client->PullDataChangeNotification(2*1000);
    if (!is_null($EventArgs)) {
        // Handle the notification event
        print $EventArgs->ToString();
        print "\n";
    }
} while (time() < $endTime);

# This example shows how to subscribe to changes of multiple monitored items, pull events, and display each change.
#
# The Python for Windows (pywin32) extensions package is needed. Install it using "pip install pypiwin32".
# CAUTION: We now recommend using Python.NET package instead. Full set of examples with Python.NET is available!
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
import time
import win32com.client

# Instantiate the client object
client = win32com.client.Dispatch('OpcLabs.EasyOpc.UA.EasyUAClient') 
# In order to use event pull, you must set a non-zero queue capacity upfront.
client.PullDataChangeNotificationQueueCapacity = 1000

print('Subscribing...')
monitoringParameters = win32com.client.Dispatch('OpcLabs.EasyOpc.UA.UAMonitoringParameters')
monitoringParameters.SamplingInterval = 1000

monitoredItemArguments1 = win32com.client.Dispatch('OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments')
monitoredItemArguments1.EndpointDescriptor.UrlString = 'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer'
monitoredItemArguments1.NodeDescriptor.NodeId.ExpandedText = 'nsu=http://test.org/UA/Data/ ;i=10845'
monitoredItemArguments1.MonitoringParameters = monitoringParameters

monitoredItemArguments2 = win32com.client.Dispatch('OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments')
monitoredItemArguments2.EndpointDescriptor.UrlString = 'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer'
monitoredItemArguments2.NodeDescriptor.NodeId.ExpandedText = 'nsu=http://test.org/UA/Data/ ;i=10853'
monitoredItemArguments2.MonitoringParameters = monitoringParameters

monitoredItemArguments3 = win32com.client.Dispatch('OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments')
monitoredItemArguments3.EndpointDescriptor.UrlString = 'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer'
monitoredItemArguments3.NodeDescriptor.NodeId.ExpandedText = 'nsu=http://test.org/UA/Data/ ;i=10855'
monitoredItemArguments3.MonitoringParameters = monitoringParameters

arguments = [
    monitoredItemArguments1,
    monitoredItemArguments2,
    monitoredItemArguments3
    ]
client.SubscribeMultipleMonitoredItems(arguments)

print('Processing data change events for 1 minute...')
endTime = time.time() + 60
while time.time() < endTime:
    eventArgs = client.PullDataChangeNotification(2*1000)
    if eventArgs is not None:
        # Handle the notification event
        print(eventArgs)

Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

Reference

_EasyUAClient Interface
_EasyUAClient Members

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Missing some example? Ask us for it on our Online Forums! You do not have to own a commercial license in order to use Online Forums, and we reply to every post.