Client and Subscriber Development > Development Models > Imperative Programming Model > Imperative Programming Model for OPC Data (Classic and UA) > Subscribing to Information (OPC Data) > Subscribing to OPC UA Data Changes |
Subscription is initiated by calling one of the SubscribeMonitoredItem, SubscribeDataChange, or SubscribeMultipleMonitoredItems method. For any significant change in the subscribed item, your application will receive the DataChangeNotification event notification, described further below. Obviously, you first need to hook up event handler for that event, and in order to prevent event loss, you should do it before subscribing. Alternatively, you can pass a callback method into the SubscribeMonitoredItem, SubscribeDataChange or SubscribeMultipleMonitoredItems call.
Some items may be changing quite frequently, and receiving all changes that are generated is not desirable for performance reasons; there are also physical limitations to the event throughput in the system. You may also want to influence the amount of received information, or control how and how often the information is delivered. OPC Data Client-UA has two sets of parameters for this: subscription parameters and monitoring parameters.
Subscription parameters (can be fully contained in UASubscriptionParameters object) influence the information delivery. Main subscription parameters are the relative priority, and publishing interval (in milliseconds). The publishing interval defines the cyclic rate that the subscription is requested to return notifications to the client.
Monitoring parameters (can be fully contained in UAMonitoringParameters object) influence which information is delivered to the client. Main monitoring parameters are the data change filter (optional), size of monitored item queue, and sampling interval (in milliseconds; it is the fastest rate at which the monitored items should be accessed and evaluated).
The data change filter, if present, is contained in the UADataChangeFilter object, and defines the conditions under which a data change notification should be reported and, optionally, a deadband for value changes where no notification is generated. The Trigger property selects whether a notification is generated only when the status code associated with the value changes, or either the status code or the value change, or if any of the status code, value, or a source timestamp change. The DeadbandType property determines the type of deadband used, and can either select no deadband, absolute deadband, or percent deadband.
There are implicit conversions available from System.Double and UADataChangeTrigger to UADataChangeFilter. This allows the developer to simply use the absolute deadband, or the trigger selection, in place of any data change filter.
In order to make the settings of various parameters easier, OPC Data Client-UA allows you to omit the specification of publishing interval in subscription parameters by leaving it at zero (the default). In this case, the component will calculate the publishing interval by dividing the sampling interval by the so-called automatic publishing factor (EasyUAClient.SharedParameters.EngineParameters.AutomaticPublishingFactor) with a default pre-set by the component. The resulting value is limited by the value of EasyUAClient.SharedParameters.EngineParameters.FastestAutomaticPublishingInterval property. This algorithm should determine a suitable publishing interval in the most common cases.
If you want to subscribe to a specific value in OPC address space, call the SubscribeDataChange or SubscribeMonitoredItem method. These methods have number of overloads, but in its simplest form, only three arguments are necessary: an endpoint descriptor, node ID, and a sampling interval. Other callbacks allow you to specify e.g. the callback method, a user-defined state object, absolute deadband value, or pass in a full set of parameters using EasyUAMonitoredItemArguments object. The SubscribeDataChange and SubscribeMonitoredItem methods return a subscription handle that you can later use to change the subscription parameters, or unsubscribe.
It is common to pass in a State argument of type Object. When the monitored item’s value changes, the State argument is then passed to the DataChangeNotification event handler (or your callback method) in the EasyUADataChangeNotificationEventArgs.Arguments object.
The State argument is typically used to provide some sort of correlation between objects in your application, and the event notifications. For example, if you are programming an HMI application and you want the event handler to update the control that displays the item’s value, you may want to set the State argument to the control object itself. When the event notification arrives, you simply update the control indicated by the State property of EasyUADataChangeNotificationEventArgs.Arguments, without having to look it up by Node Id or so. See Use the state instead of handles to identify subscribed entities.
// This example shows how to subscribe to changes of a single monitored item and display the value of the item with each // change. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . using System; using OpcLabs.EasyOpc.UA; using OpcLabs.EasyOpc.UA.OperationModel; namespace UADocExamples._EasyUAClient { partial class SubscribeDataChange { public static void Overload1() { 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 and hook events. var client = new EasyUAClient(); client.DataChangeNotification += client_DataChangeNotification; Console.WriteLine("Subscribing..."); client.SubscribeDataChange(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000); Console.WriteLine("Processing data change events for 20 seconds..."); System.Threading.Thread.Sleep(20 * 1000); Console.WriteLine("Unsubscribing..."); client.UnsubscribeAllMonitoredItems(); Console.WriteLine("Waiting for 5 seconds..."); System.Threading.Thread.Sleep(5 * 1000); Console.WriteLine("Finished."); } static void client_DataChangeNotification(object sender, EasyUADataChangeNotificationEventArgs e) { // Display value. if (e.Succeeded) Console.WriteLine($"Value: {e.AttributeData.Value}"); else Console.WriteLine($"*** Failure: {e.ErrorMessageBrief}"); } } }
# This example shows how to subscribe to changes of a single monitored item and display the value of the item with each # change. # # Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . #requires -Version 5.1 using namespace OpcLabs.EasyOpc.UA # The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows . Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUA.dll" Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUAComponents.dll" [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. $client = New-Object EasyUAClient # Data change notification handler Register-ObjectEvent -InputObject $client -EventName DataChangeNotification -Action { # Display value. if ($EventArgs.Succeeded) { Write-Host "Value: $($EventArgs.AttributeData.Value)" } else { Write-Host "*** Failure: $($EventArgs.ErrorMessageBrief)" } } Write-Host "Subscribing..." $client.SubscribeDataChange($endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000) Write-Host "Processing data change events for 20 seconds..." $stopwatch = [System.Diagnostics.Stopwatch]::StartNew() while ($stopwatch.Elapsed.TotalSeconds -lt 20) { Start-Sleep -Seconds 1 } Write-Host "Unsubscribing..." $client.UnsubscribeAllMonitoredItems() Write-Host "Waiting for 5 seconds..." Start-Sleep -Seconds 5 Write-Host "Finished."
# This example shows how to subscribe to changes of a single monitored item and display the value of the item with 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 Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python . # 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, e): # Display value. if e.Succeeded: print('Value: ', e.AttributeData.Value, sep='') else: print('*** Failure: ', e.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 and hook events. client = EasyUAClient() client.DataChangeNotification += dataChangeNotification print('Subscribing...') IEasyUAClientExtension.SubscribeDataChange(client, endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'), 1000) print('Processing data change events for 20 seconds...') time.sleep(20) print('Unsubscribing...') client.UnsubscribeAllMonitoredItems() print('Waiting for 5 seconds...') time.sleep(5) print('Finished.')
' This example shows how to subscribe to changes of a single monitored item and display the value of the item with each change. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Imports OpcLabs.EasyOpc.UA Imports OpcLabs.EasyOpc.UA.OperationModel Namespace _EasyUAClient Friend Class SubscribeDataChange Public Shared Sub Overload1() ' Define which server we will work with. 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 and hook events Dim client = New EasyUAClient() AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification Console.WriteLine("Subscribing...") client.SubscribeDataChange(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000) Console.WriteLine("Processing monitored item changed events for 10 seconds...") Threading.Thread.Sleep(10 * 1000) Console.WriteLine("Unsubscribing...") client.UnsubscribeAllMonitoredItems() Console.WriteLine("Waiting for 5 seconds...") Threading.Thread.Sleep(5 * 1000) End Sub Private Shared Sub client_DataChangeNotification(ByVal sender As Object, ByVal e As EasyUADataChangeNotificationEventArgs) ' Display value If e.Succeeded Then Console.WriteLine("Value: {0}", e.AttributeData.Value) Else Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief) End If End Sub End Class End Namespace
// This example shows how to subscribe to changes of a single monitored item and display each change. // // Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . #include "stdafx.h" // Includes "QuickOpc.h", and other commonly used files #include <atlcom.h> #include "SubscribeDataChange.h" namespace _EasyUAClient { // CEasyUAClientEvents class CEasyUAClientEvents : public IDispEventImpl<1, CEasyUAClientEvents> { public: BEGIN_SINK_MAP(CEasyUAClientEvents) // Event handlers must have the __stdcall calling convention SINK_ENTRY(1, DISPID_EASYUACLIENTEVENTS_DATACHANGENOTIFICATION, &CEasyUAClientEvents::DataChangeNotification) END_SINK_MAP() public: // The handler for EasyUAClient.DataChangeNotification event STDMETHOD(DataChangeNotification)(VARIANT varSender, _EasyUADataChangeNotificationEventArgs* pEventArgs) { // Display the data // Remark: Production code would check EventArgsPtr->Exception before accessing EventArgsPtr->AttributeData. _UAAttributeDataPtr AttributeDataPtr(pEventArgs->AttributeData); _tprintf(_T("%s\n"), (LPCTSTR)CW2CT(AttributeDataPtr->ToString)); return S_OK; } }; void SubscribeDataChange::Main() { // Initialize the COM library CoInitializeEx(NULL, COINIT_MULTITHREADED); { // Instantiate the client object _EasyUAClientPtr ClientPtr(__uuidof(EasyUAClient)); // Hook events CEasyUAClientEvents* pClientEvents = new CEasyUAClientEvents(); AtlGetObjectSourceInterface(ClientPtr, &pClientEvents->m_libid, &pClientEvents->m_iid, &pClientEvents->m_wMajorVerNum, &pClientEvents->m_wMinorVerNum); pClientEvents->m_iid = _uuidof(DEasyUAClientEvents); pClientEvents->DispEventAdvise(ClientPtr, &pClientEvents->m_iid); // _tprintf(_T("Subscribing...\n")); ClientPtr->SubscribeDataChange( //L"http://opcua.demo-this.com:51211/UA/SampleServer", L"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer", L"nsu=http://test.org/UA/Data/ ;i=10853", 1000); _tprintf(_T("Processing monitored item changed events for 1 minute...\n")); Sleep(60*1000); // Unhook events pClientEvents->DispEventUnadvise(ClientPtr, &pClientEvents->m_iid); } // Release all interface pointers BEFORE calling CoUninitialize() CoUninitialize(); } }
// This example shows how to subscribe to changes of a single monitored item // and display each change. // // Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . type TClientEventHandlers = class procedure OnDataChangeNotification( Sender: TObject; sender0: OleVariant; eventArgs: _EasyUADataChangeNotificationEventArgs); end; procedure TClientEventHandlers.OnDataChangeNotification( Sender: TObject; sender0: OleVariant; eventArgs: _EasyUADataChangeNotificationEventArgs); begin // Display the data // Remark: Production code would check eventArgs.Exception before accessing // eventArgs.AttributeData. WriteLn(eventArgs.Arguments.NodeDescriptor.ToString, ': ', eventArgs.AttributeData.ToString); end; class procedure SubscribeDataChange.Main; var Client: EasyUAClient; EvsClient: TEvsEasyUAClient; ClientEventHandlers: TClientEventHandlers; begin // Instantiate the client object and hook events EvsClient := TEvsEasyUAClient.Create(nil); Client := EvsClient.ComServer; ClientEventHandlers := TClientEventHandlers.Create; EvsClient.OnDataChangeNotification := @ClientEventHandlers.OnDataChangeNotification; 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...'); PumpSleep(60*1000); end;
// This example shows how to subscribe to changes of a single monitored item // and display each change. // // Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . type TClientEventHandlers121 = class procedure OnDataChangeNotification( ASender: TObject; sender: OleVariant; const eventArgs: _EasyUADataChangeNotificationEventArgs); end; procedure TClientEventHandlers121.OnDataChangeNotification( ASender: TObject; sender: OleVariant; const eventArgs: _EasyUADataChangeNotificationEventArgs); begin // Display the data if eventArgs.Succeeded then WriteLn(eventArgs.Arguments.NodeDescriptor.ToString, ': ', eventArgs.AttributeData.ToString) else WriteLn(eventArgs.Arguments.NodeDescriptor.ToString, ' *** Failure: ', eventArgs.ErrorMessageBrief); end; class procedure SubscribeDataChange.Main; var Client: TEasyUAClient; ClientEventHandlers: TClientEventHandlers121; begin // Instantiate the client object and hook events Client := TEasyUAClient.Create(nil); ClientEventHandlers := TClientEventHandlers121.Create; Client.OnDataChangeNotification := ClientEventHandlers.OnDataChangeNotification; 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...'); PumpSleep(60*1000); WriteLn('Unsubscribing...'); Client.UnsubscribeAllMonitoredItems; WriteLn('Waiting for 5 seconds...'); PumpSleep(5*1000); WriteLn('Finished.'); FreeAndNil(Client); FreeAndNil(ClientEventHandlers); end;
// This example shows how to subscribe to changes of a single monitored item and display each change. // // Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . class ClientEvents { function DataChangeNotification($Sender, $E) { // Display the data if ($E->Succeeded) printf("%s\n", $E->AttributeData); else printf("*** Failure : %s\n", $E->ErrorMessageBrief); } } // Instantiate the client object and hook events $Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient"); $ClientEvents = new ClientEvents(); com_event_sink($Client, $ClientEvents, "DEasyUAClientEvents"); printf("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); printf("Processing monitored item changed events for 1 minute...\n"); $startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 60);
REM This example shows how to subscribe to changes of a single monitored item and display each change. REM REM Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . ' The client object, with events 'Public WithEvents Client1 As EasyUAClient Public Sub SubscribeDataChange_Main_Command_Click() OutputText = "" Set Client1 = New EasyUAClient OutputText = OutputText & "Subscribing..." & vbCrLf Call Client1.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 Pause 60000 OutputText = OutputText & "Unsubscribing..." & vbCrLf Client1.UnsubscribeAllMonitoredItems OutputText = OutputText & "Waiting for 5 seconds..." & vbCrLf Pause 5000 OutputText = OutputText & "Finished." & vbCrLf Set Client1 = Nothing End Sub Public Sub Client1_DataChangeNotification(ByVal sender As Variant, ByVal eventArgs As EasyUADataChangeNotificationEventArgs) ' Display the data If eventArgs.Exception Is Nothing Then OutputText = OutputText & eventArgs.AttributeData & vbCrLf Else OutputText = OutputText & eventArgs.ErrorMessageBrief & vbCrLf End If End Sub
Rem This example shows how to subscribe to changes of a single monitored item and display each change. Rem Rem Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Option Explicit ' Instantiate the client object and hook events Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient") WScript.ConnectObject Client, "Client_" 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 monitored item changed events for 1 minute..." WScript.Sleep 60*1000 Sub Client_DataChangeNotification(Sender, e) ' Display the data Dim display: If e.Exception Is Nothing Then display = e.AttributeData Else display = e.ErrorMessageBrief WScript.Echo display End Sub
To subscribe to multiple items simultaneously in an efficient manner, call the SubscribeMultipleMonitoredItems method (instead of multiple SubscribeDataChange or SubscribeMonitoredItem calls in a loop). You receive back an array of subscription handles. You pass in an array of EasyUAMonitoredItemArguments objects (each containing information for a single subscription to be made), to the SubscribeMultipleMonitoredItems method.
// This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with // each change. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . using System; using OpcLabs.EasyOpc.UA; using OpcLabs.EasyOpc.UA.OperationModel; namespace UADocExamples._EasyUAClient { partial class SubscribeMultipleMonitoredItems { public static void Main1() { 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 and hook events. var client = new EasyUAClient(); client.DataChangeNotification += client_DataChangeNotification_Main1; Console.WriteLine("Subscribing..."); client.SubscribeMultipleMonitoredItems(new[] { new EasyUAMonitoredItemArguments(null, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10845", 1000), new EasyUAMonitoredItemArguments(null, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000), new EasyUAMonitoredItemArguments(null, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10855", 1000) }); Console.WriteLine("Processing monitored item changed events for 10 seconds..."); System.Threading.Thread.Sleep(10 * 1000); Console.WriteLine("Unsubscribing..."); client.UnsubscribeAllMonitoredItems(); Console.WriteLine("Waiting for 5 seconds..."); System.Threading.Thread.Sleep(5 * 1000); Console.WriteLine("Finished."); } static void client_DataChangeNotification_Main1(object sender, EasyUADataChangeNotificationEventArgs e) { // Display value. if (e.Succeeded) Console.WriteLine($"{e.Arguments.NodeDescriptor}: {e.AttributeData.Value}"); else Console.WriteLine($"{e.Arguments.NodeDescriptor} *** Failure: {e.ErrorMessageBrief}"); } } }
# This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with # each change. # # Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . #requires -Version 5.1 using namespace OpcLabs.EasyOpc.UA using namespace OpcLabs.EasyOpc.UA.OperationModel # The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows . Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUA.dll" Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUAComponents.dll" [UAEndpointDescriptor]$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. $client = New-Object EasyUAClient # Data change notification handler Register-ObjectEvent -InputObject $client -EventName DataChangeNotification -Action { # Display value. if ($EventArgs.Succeeded) { Write-Host "$($EventArgs.Arguments.NodeDescriptor): $($EventArgs.AttributeData.Value)" } else { Write-Host "$($EventArgs.Arguments.NodeDescriptor) *** Failure: $($EventArgs.ErrorMessageBrief)" } } Write-Host "Subscribing..." $handleArray = $client.SubscribeMultipleMonitoredItems(@( (New-Object UAMonitoredItemArguments( (New-Object UAAttributeArguments($endpointDescriptor, [UANodeDescriptor]"nsu=http://test.org/UA/Data/ ;i=10845")), 1000)), (New-Object UAMonitoredItemArguments( (New-Object UAAttributeArguments($endpointDescriptor, [UANodeDescriptor]"nsu=http://test.org/UA/Data/ ;i=10853")), 1000)), (New-Object UAMonitoredItemArguments( (New-Object UAAttributeArguments($endpointDescriptor, [UANodeDescriptor]"nsu=http://test.org/UA/Data/ ;i=10855")), 1000)) )) Write-Host Write-Host "Processing monitored item changed events for 10 seconds..." $stopwatch = [System.Diagnostics.Stopwatch]::StartNew() while ($stopwatch.Elapsed.TotalSeconds -lt 10) { Start-Sleep -Seconds 1 } Write-Host "Unsubscribing..." $client.UnsubscribeAllMonitoredItems() Write-Host "Waiting for 5 seconds..." Start-Sleep -Seconds 5 Write-Host "Finished."
# This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item # with 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 Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python . # 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, e): # Display value. if e.Succeeded: print(e.Arguments.NodeDescriptor, ': ', e.AttributeData.Value, sep='') else: print(e.Arguments.NodeDescriptor, ' *** Failure: ', e.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 and hook events. client = EasyUAClient() client.DataChangeNotification += dataChangeNotification print('Subscribing...') client.SubscribeMultipleMonitoredItems([ EasyUAMonitoredItemArguments( None, endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10845'), UAMonitoringParameters(1000)), EasyUAMonitoredItemArguments( None, endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'), UAMonitoringParameters(1000)), EasyUAMonitoredItemArguments( None, endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10855'), UAMonitoringParameters(1000)), ]) print('Processing data change events for 10 seconds...') time.sleep(10) print('Unsubscribing...') client.UnsubscribeAllMonitoredItems() print('Waiting for 5 seconds...') time.sleep(5) print('Finished.')
' This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with ' each change. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Imports OpcLabs.EasyOpc.UA Imports OpcLabs.EasyOpc.UA.OperationModel Namespace _EasyUAClient Partial Friend Class SubscribeMultipleMonitoredItems Public Shared Sub Main1() ' Define which server we will work with. 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 and hook events Dim client = New EasyUAClient() AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification Console.WriteLine("Subscribing...") client.SubscribeMultipleMonitoredItems(New EasyUAMonitoredItemArguments() _ { New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10845", 1000), New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000), New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10855", 1000) } ) Console.WriteLine("Processing monitored item changed events for 10 seconds...") Threading.Thread.Sleep(10 * 1000) Console.WriteLine("Unsubscribing...") client.UnsubscribeAllMonitoredItems() Console.WriteLine("Waiting for 5 seconds...") Threading.Thread.Sleep(5 * 1000) End Sub Private Shared Sub client_DataChangeNotification(ByVal sender As Object, ByVal e As EasyUADataChangeNotificationEventArgs) ' Display value If e.Succeeded Then Console.WriteLine($"{e.Arguments.NodeDescriptor}: {e.AttributeData.Value}") Else Console.WriteLine($"{e.Arguments.NodeDescriptor} *** Failure: {e.ErrorMessageBrief}") End If End Sub End Class End Namespace
// This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with // each change. // // Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . #include "stdafx.h" // Includes "QuickOpc.h", and other commonly used files #include <atlcom.h> #include <atlsafe.h> #include "SubscribeMultipleMonitoredItems.h" namespace _EasyUAClient { // CEasyUAClientEvents class CEasyUAClientEvents : public IDispEventImpl<1, CEasyUAClientEvents> { public: BEGIN_SINK_MAP(CEasyUAClientEvents) // Event handlers must have the __stdcall calling convention SINK_ENTRY(1, DISPID_EASYUACLIENTEVENTS_DATACHANGENOTIFICATION, &CEasyUAClientEvents::DataChangeNotification) END_SINK_MAP() public: // The handler for EasyUAClient.DataChangeNotification event STDMETHOD(DataChangeNotification)(VARIANT varSender, _EasyUADataChangeNotificationEventArgs* pEventArgs) { // Display the data _tprintf(_T("%s: "), (LPCTSTR)CW2CT(pEventArgs->Arguments->NodeDescriptor->ToString)); // Remark: Production code would check EventArgsPtr->Exception before accessing EventArgsPtr->AttributeData. _UAAttributeDataPtr AttributeDataPtr(pEventArgs->AttributeData); _tprintf(_T("%s\n"), (LPCTSTR)CW2CT(AttributeDataPtr->ToString)); return S_OK; } }; void SubscribeMultipleMonitoredItems::Main() { // Initialize the COM library CoInitializeEx(NULL, COINIT_MULTITHREADED); { // Instantiate the client object _EasyUAClientPtr ClientPtr(__uuidof(EasyUAClient)); // Hook events CEasyUAClientEvents* pClientEvents = new CEasyUAClientEvents(); AtlGetObjectSourceInterface(ClientPtr, &pClientEvents->m_libid, &pClientEvents->m_iid, &pClientEvents->m_wMajorVerNum, &pClientEvents->m_wMinorVerNum); pClientEvents->m_iid = _uuidof(DEasyUAClientEvents); pClientEvents->DispEventAdvise(ClientPtr, &pClientEvents->m_iid); // _tprintf(_T("Subscribing...\n")); _UAMonitoringParametersPtr MonitoringParametersPtr(_uuidof(UAMonitoringParameters)); MonitoringParametersPtr->SamplingInterval = 1000; _UAMonitoredItemArgumentsPtr MonitoringArguments1Ptr(_uuidof(EasyUAMonitoredItemArguments)); MonitoringArguments1Ptr->EndpointDescriptor->UrlString = //L"http://opcua.demo-this.com:51211/UA/SampleServer"; L"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"; MonitoringArguments1Ptr->NodeDescriptor->NodeId->ExpandedText = L"nsu=http://test.org/UA/Data/ ;i=10845"; MonitoringArguments1Ptr->MonitoringParameters = MonitoringParametersPtr; _UAMonitoredItemArgumentsPtr MonitoringArguments2Ptr(_uuidof(EasyUAMonitoredItemArguments)); MonitoringArguments2Ptr->EndpointDescriptor->UrlString = //L"http://opcua.demo-this.com:51211/UA/SampleServer"; L"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"; MonitoringArguments2Ptr->NodeDescriptor->NodeId->ExpandedText = L"nsu=http://test.org/UA/Data/ ;i=10853"; MonitoringArguments2Ptr->MonitoringParameters = MonitoringParametersPtr; _UAMonitoredItemArgumentsPtr MonitoringArguments3Ptr(_uuidof(EasyUAMonitoredItemArguments)); MonitoringArguments3Ptr->EndpointDescriptor->UrlString = //L"http://opcua.demo-this.com:51211/UA/SampleServer"; L"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"; MonitoringArguments3Ptr->NodeDescriptor->NodeId->ExpandedText = L"nsu=http://test.org/UA/Data/ ;i=10855"; MonitoringArguments3Ptr->MonitoringParameters = MonitoringParametersPtr; CComSafeArray<VARIANT> arguments(3); arguments.SetAt(0, _variant_t((IDispatch*)MonitoringArguments1Ptr)); arguments.SetAt(1, _variant_t((IDispatch*)MonitoringArguments2Ptr)); arguments.SetAt(2, _variant_t((IDispatch*)MonitoringArguments3Ptr)); CComVariant vArguments(arguments); CComSafeArray<VARIANT> handles; handles.Attach(ClientPtr->SubscribeMultipleMonitoredItems(&vArguments)); for (int i = handles.GetLowerBound(); i <= handles.GetUpperBound(); i++) { _variant_t vString; vString.ChangeType(VT_BSTR, &_variant_t(handles[i])); _tprintf(_T("handleArray(d)s\n"), i, (LPCTSTR)CW2CT((_bstr_t)vString)); } _tprintf(_T("Processing monitored item changed events for 10 seconds...\n")); Sleep(10*1000); _tprintf(_T("Unsubscribing...\n")); ClientPtr->UnsubscribeAllMonitoredItems(); _tprintf(_T("Waiting for 5 seconds...\n")); Sleep(5*1000); // Unhook events pClientEvents->DispEventUnadvise(ClientPtr, &pClientEvents->m_iid); } // Release all interface pointers BEFORE calling CoUninitialize() CoUninitialize(); } }
// This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with // each change. // // Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . { type TClientEventHandlers = class procedure OnDataChangeNotification( Sender: TObject; sender0: OleVariant; eventArgs: _EasyUADataChangeNotificationEventArgs); end; procedure TClientEventHandlers.OnDataChangeNotification( Sender: TObject; sender0: OleVariant; eventArgs: _EasyUADataChangeNotificationEventArgs); begin // Display the data // Remark: Production code would check eventArgs.Exception before accessing // eventArgs.AttributeData. WriteLn(eventArgs.Arguments.NodeDescriptor.ToString, ': ', eventArgs.AttributeData.ToString); end; } class procedure SubscribeMultipleMonitoredItems.Main; var Arguments: OleVariant; EvsClient: TEvsEasyUAClient; Client: EasyUAClient; ClientEventHandlers: TClientEventHandlers; Handle: Cardinal; HandleArray: OleVariant; I: Cardinal; MonitoredItemArguments1, MonitoredItemArguments2, MonitoredItemArguments3: _EasyUAMonitoredItemArguments; MonitoringParameters: _UAMonitoringParameters; begin // Instantiate the client object and hook events EvsClient := TEvsEasyUAClient.Create(nil); Client := EvsClient.ComServer; ClientEventHandlers := TClientEventHandlers.Create; EvsClient.OnDataChangeNotification := @ClientEventHandlers.OnDataChangeNotification; WriteLn('Subscribing...'); MonitoringParameters := CoUAMonitoringParameters.Create; MonitoringParameters.SamplingInterval := 1000; MonitoredItemArguments1 := CoEasyUAMonitoredItemArguments.Create; MonitoredItemArguments1.EndpointDescriptor.UrlString := //'http://opcua.demo-this.com:51211/UA/SampleServer'; '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 := CoEasyUAMonitoredItemArguments.Create; MonitoredItemArguments2.EndpointDescriptor.UrlString := //'http://opcua.demo-this.com:51211/UA/SampleServer'; '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 := CoEasyUAMonitoredItemArguments.Create; MonitoredItemArguments3.EndpointDescriptor.UrlString := //'http://opcua.demo-this.com:51211/UA/SampleServer'; '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 := VarArrayCreate([0, 2], varVariant); Arguments[0] := MonitoredItemArguments1; Arguments[1] := MonitoredItemArguments2; Arguments[2] := MonitoredItemArguments3; TVarData(HandleArray).VType := varArray or varVariant; TVarData(HandleArray).VArray := PVarArray( Client.SubscribeMultipleMonitoredItems(PSafeArray(TVarData(Arguments).VArray))); for I := VarArrayLowBound(HandleArray, 1) to VarArrayHighBound(HandleArray, 1) do begin Handle := Cardinal(HandleArray[I]); WriteLn('HandleArray[', I, ']: ', Handle); end; WriteLn('Processing monitored item changed events for 10 seconds...'); PumpSleep(10*1000); WriteLn('Unsubscribing...'); Client.UnsubscribeAllMonitoredItems; WriteLn('Waiting for 5 seconds...'); Sleep(5*1000); WriteLn('Finished...'); end;
// This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with // each change. // // Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . type TClientEventHandlers123 = class procedure OnDataChangeNotification( ASender: TObject; sender: OleVariant; const eventArgs: _EasyUADataChangeNotificationEventArgs); end; procedure TClientEventHandlers123.OnDataChangeNotification( ASender: TObject; sender: OleVariant; const eventArgs: _EasyUADataChangeNotificationEventArgs); begin // Display the data if eventArgs.Succeeded then WriteLn(eventArgs.Arguments.NodeDescriptor.ToString, ': ', eventArgs.AttributeData.ToString) else WriteLn(eventArgs.Arguments.NodeDescriptor.ToString, ' *** Failure: ', eventArgs.ErrorMessageBrief); end; class procedure SubscribeMultipleMonitoredItems.Main; var Arguments: OleVariant; Client: TEasyUAClient; ClientEventHandlers: TClientEventHandlers123; Handle: Cardinal; HandleArray: OleVariant; I: Cardinal; MonitoredItemArguments1, MonitoredItemArguments2, MonitoredItemArguments3: _EasyUAMonitoredItemArguments; MonitoringParameters: _UAMonitoringParameters; begin // Instantiate the client object and hook events Client := TEasyUAClient.Create(nil); ClientEventHandlers := TClientEventHandlers123.Create; Client.OnDataChangeNotification := ClientEventHandlers.OnDataChangeNotification; WriteLn('Subscribing...'); MonitoringParameters := CoUAMonitoringParameters.Create; MonitoringParameters.SamplingInterval := 1000; MonitoredItemArguments1 := CoEasyUAMonitoredItemArguments.Create; MonitoredItemArguments1.EndpointDescriptor.UrlString := //'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'; MonitoredItemArguments1.NodeDescriptor.NodeId.ExpandedText := 'nsu=http://test.org/UA/Data/ ;i=10845'; MonitoredItemArguments1.MonitoringParameters := MonitoringParameters; MonitoredItemArguments2 := CoEasyUAMonitoredItemArguments.Create; MonitoredItemArguments2.EndpointDescriptor.UrlString := //'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'; MonitoredItemArguments2.NodeDescriptor.NodeId.ExpandedText := 'nsu=http://test.org/UA/Data/ ;i=10853'; MonitoredItemArguments2.MonitoringParameters := MonitoringParameters; MonitoredItemArguments3 := CoEasyUAMonitoredItemArguments.Create; MonitoredItemArguments3.EndpointDescriptor.UrlString := //'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'; MonitoredItemArguments3.NodeDescriptor.NodeId.ExpandedText := 'nsu=http://test.org/UA/Data/ ;i=10855'; MonitoredItemArguments3.MonitoringParameters := MonitoringParameters; Arguments := VarArrayCreate([0, 2], varVariant); Arguments[0] := MonitoredItemArguments1; Arguments[1] := MonitoredItemArguments2; Arguments[2] := MonitoredItemArguments3; TVarData(HandleArray).VType := varArray or varVariant; TVarData(HandleArray).VArray := PVarArray( Client.SubscribeMultipleMonitoredItems(Arguments)); for I := VarArrayLowBound(HandleArray, 1) to VarArrayHighBound(HandleArray, 1) do begin Handle := Cardinal(HandleArray[I]); WriteLn('HandleArray[', I, ']: ', Handle); end; WriteLn('Processing monitored item changed events for 10 seconds...'); PumpSleep(10*1000); WriteLn('Unsubscribing...'); Client.UnsubscribeAllMonitoredItems; WriteLn('Waiting for 5 seconds...'); Sleep(5*1000); WriteLn('Finished.'); VarClear(HandleArray); VarClear(Arguments); FreeAndNil(Client); FreeAndNil(ClientEventHandlers); end;
// This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with // each change. // // Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . class ClientEvents { function DataChangeNotification($Sender, $E) { // Display the data if ($E->Succeeded) printf("s: s\n", $E->Arguments->NodeDescriptor, $E->AttributeData); else printf("s *** Failures\n", $E->Arguments->NodeDescriptor, $E->ErrorMessageBrief); } } // Instantiate the client object and hook events $Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient"); $ClientEvents = new ClientEvents(); com_event_sink($Client, $ClientEvents, "DEasyUAClientEvents"); printf("Subscribing...\n"); $MonitoringParameters = new COM("OpcLabs.EasyOpc.UA.UAMonitoringParameters"); $MonitoringParameters->SamplingInterval = 1000; $MonitoredItemArguments1 = new COM("OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments"); $MonitoredItemArguments1->EndpointDescriptor->UrlString = //"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"; $MonitoredItemArguments1->NodeDescriptor->NodeId->ExpandedText = "nsu=http://test.org/UA/Data/ ;i=10845"; $MonitoredItemArguments1->MonitoringParameters = $MonitoringParameters; $MonitoredItemArguments2 = new COM("OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments"); $MonitoredItemArguments2->EndpointDescriptor->UrlString = //"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"; $MonitoredItemArguments2->NodeDescriptor->NodeId->ExpandedText = "nsu=http://test.org/UA/Data/ ;i=10853"; $MonitoredItemArguments2->MonitoringParameters = $MonitoringParameters; $MonitoredItemArguments3 = new COM("OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments"); $MonitoredItemArguments3->EndpointDescriptor->UrlString = //"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"; $MonitoredItemArguments3->NodeDescriptor->NodeId->ExpandedText = "nsu=http://test.org/UA/Data/ ;i=10855"; $MonitoredItemArguments3->MonitoringParameters = $MonitoringParameters; $arguments[0] = $MonitoredItemArguments1; $arguments[1] = $MonitoredItemArguments2; $arguments[2] = $MonitoredItemArguments3; $handleArray = $Client->SubscribeMultipleMonitoredItems($arguments); for ($i = 0; $i < count($handleArray); $i++) { printf("handleArray[d]d\n", $i, $handleArray[$i]); } printf("Processing monitored item changed events for 10 seconds...\n"); $startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 10); printf("Unsubscribing...\n"); $Client->UnsubscribeAllMonitoredItems; printf("Waiting for 5 seconds...\n"); $startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 5);
REM This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with REM each change. REM REM Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . ' The client object, with events 'Public WithEvents Client2 As EasyUAClient Public Sub SubscribeMultipleMonitoredItems_Main_Command_Click() OutputText = "" Set Client2 = New EasyUAClient OutputText = OutputText & "Subscribing..." & vbCrLf Dim MonitoringParameters As New UAMonitoringParameters MonitoringParameters.SamplingInterval = 1000 Dim MonitoredItemArguments1 As New 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" Set MonitoredItemArguments1.MonitoringParameters = MonitoringParameters MonitoredItemArguments1.SetState ("Item1") Dim MonitoredItemArguments2 As New 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" Set MonitoredItemArguments2.MonitoringParameters = MonitoringParameters MonitoredItemArguments2.SetState ("Item2") Dim MonitoredItemArguments3 As New 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" Set MonitoredItemArguments3.MonitoringParameters = MonitoringParameters MonitoredItemArguments3.SetState ("Item3") Dim arguments(2) As Variant Set arguments(0) = MonitoredItemArguments1 Set arguments(1) = MonitoredItemArguments2 Set arguments(2) = MonitoredItemArguments3 Dim handleArray As Variant handleArray = Client2.SubscribeMultipleMonitoredItems(arguments) Dim i As Long: For i = LBound(handleArray) To UBound(handleArray) OutputText = OutputText & "handleArray(" & i & "): " & handleArray(i) & vbCrLf Next OutputText = OutputText & "Processing monitored item changed events for 10 seconds..." & vbCrLf Pause 10000 OutputText = OutputText & "Unsubscribing..." & vbCrLf Call Client2.UnsubscribeAllMonitoredItems OutputText = OutputText & "Waiting for 5 seconds..." & vbCrLf Pause 5000 Set Client2 = Nothing OutputText = OutputText & "Finished." & vbCrLf End Sub Public Sub Client2_DataChangeNotification(ByVal sender As Variant, ByVal eventArgs As EasyUADataChangeNotificationEventArgs) ' Display the data If eventArgs.Exception Is Nothing Then OutputText = OutputText & "[" & eventArgs.arguments.State & "] " & eventArgs.arguments.nodeDescriptor & ": " & eventArgs.AttributeData & vbCrLf Else OutputText = OutputText & "[" & eventArgs.arguments.State & "] " & eventArgs.arguments.nodeDescriptor & ": " & eventArgs.ErrorMessageBrief & vbCrLf End If End Sub
Rem This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with Rem each change. Rem Rem Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Option Explicit ' Instantiate the client object and hook events Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient") WScript.ConnectObject Client, "Client_" WScript.Echo "Subscribing..." Dim MonitoringParameters: Set MonitoringParameters = CreateObject("OpcLabs.EasyOpc.UA.UAMonitoringParameters") MonitoringParameters.SamplingInterval = 1000 Dim MonitoredItemArguments1: Set MonitoredItemArguments1 = CreateObject("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 Dim MonitoredItemArguments2: Set MonitoredItemArguments2 = CreateObject("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 Dim MonitoredItemArguments3: Set MonitoredItemArguments3 = CreateObject("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 Dim arguments(2) Set arguments(0) = MonitoredItemArguments1 Set arguments(1) = MonitoredItemArguments2 Set arguments(2) = MonitoredItemArguments3 Dim handleArray: handleArray = Client.SubscribeMultipleMonitoredItems(arguments) Dim i: For i = LBound(handleArray) To UBound(handleArray) WScript.Echo "handleArray(" & i & "): " & handleArray(i) Next WScript.Echo "Processing monitored item changed events for 10 seconds..." WScript.Sleep 10 * 1000 WScript.Echo "Unsubscribing..." Client.UnsubscribeAllMonitoredItems WScript.Echo "Waiting for 5 seconds..." WScript.Sleep 5 * 1000 Sub Client_DataChangeNotification(Sender, e) ' Display the data Dim display: If e.Exception Is Nothing Then display = e.AttributeData Else display = e.ErrorMessageBrief WScript.Echo e.Arguments.NodeDescriptor & ":" & display End Sub
// This example shows how to subscribe to changes of all data variables under a specified object in OPC UA address space. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . using System; using System.Linq; using OpcLabs.EasyOpc.UA; using OpcLabs.EasyOpc.UA.AddressSpace; using OpcLabs.EasyOpc.UA.OperationModel; namespace UADocExamples._EasyUAClient { partial class SubscribeMultipleMonitoredItems { public static void AllInObject() { 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 and hook events var client = new EasyUAClient(); client.DataChangeNotification += client_DataChangeNotification_AllInObject; // Obtain variables under "Scalar" node Console.WriteLine("Browsing..."); UANodeElementCollection nodeElementCollection; try { nodeElementCollection = client.BrowseDataVariables(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;ns=2;i=10787"); } catch (UAException uaException) { Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message); return; } // Create array with monitored item arguments EasyUAMonitoredItemArguments[] monitoredItemArgumentsArray = nodeElementCollection .Select(element => new EasyUAMonitoredItemArguments(null, endpointDescriptor, element)) .ToArray(); Console.WriteLine("Subscribing..."); client.SubscribeMultipleMonitoredItems(monitoredItemArgumentsArray); Console.WriteLine("Processing monitored item changed events for 20 seconds..."); System.Threading.Thread.Sleep(20 * 1000); Console.WriteLine("Unsubscribing..."); client.UnsubscribeAllMonitoredItems(); Console.WriteLine("Waiting for 5 seconds..."); System.Threading.Thread.Sleep(5 * 1000); } static void client_DataChangeNotification_AllInObject(object sender, EasyUADataChangeNotificationEventArgs e) { // Display value if (e.Succeeded) Console.WriteLine("{0}: {1}", e.Arguments.NodeDescriptor, e.AttributeData.Value); else Console.WriteLine("{0} *** Failure: {1}", e.Arguments.NodeDescriptor, e.ErrorMessageBrief); } } }
# This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item # with 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 Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python . # 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, e): # Display value. if e.Succeeded: print(e.Arguments.NodeDescriptor, ': ', e.AttributeData.Value, sep='') else: print(e.Arguments.NodeDescriptor, ' *** Failure: ', e.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 and hook events. client = EasyUAClient() client.DataChangeNotification += dataChangeNotification # Obtain variables under "Scalar" node. print('Browsing...') try: nodeElementCollection = IEasyUAClientExtension.BrowseDataVariables(client, endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;ns=2;i=10787')) except UAException as uaException: print('*** Failure: ' + uaException.GetBaseException().Message) exit() # Create array with monitored item arguments. monitoredItemArgumentsArray = list(map( lambda element: EasyUAMonitoredItemArguments(None, endpointDescriptor, element.ToUANodeDescriptor()), nodeElementCollection)) print('Subscribing...') client.SubscribeMultipleMonitoredItems(monitoredItemArgumentsArray) print('Processing data change events for 20 seconds...') time.sleep(20) print('Unsubscribing...') client.UnsubscribeAllMonitoredItems() print('Waiting for 5 seconds...') time.sleep(5) print('Finished.')
' This example shows how to subscribe to changes of all data variables under a specified object in OPC UA address space. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Imports System.Linq Imports OpcLabs.EasyOpc.UA Imports OpcLabs.EasyOpc.UA.AddressSpace Imports OpcLabs.EasyOpc.UA.OperationModel Namespace _EasyUAClient Partial Friend Class SubscribeMultipleMonitoredItems Public Shared Sub AllInObject() ' Define which server we will work with. 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 and hook events Dim client = New EasyUAClient() AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification_AllInObject ' Obtain variables under "Scalar" node Console.WriteLine("Subscribing...") Dim nodeElementCollection As UANodeElementCollection Try nodeElementCollection = client.BrowseDataVariables(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;ns=2;i=10787") Catch uaException As UAException Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message) Exit Sub End Try ' Create array with monitored item arguments Dim monitoredItemArgumentsArray() As EasyUAMonitoredItemArguments = nodeElementCollection.Select(Function(element) New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, element)).ToArray() Console.WriteLine("Subscribing...") client.SubscribeMultipleMonitoredItems(monitoredItemArgumentsArray) Console.WriteLine("Processing monitored item changed events for 20 seconds...") Threading.Thread.Sleep(20 * 1000) Console.WriteLine("Unsubscribing...") client.UnsubscribeAllMonitoredItems() Console.WriteLine("Waiting for 5 seconds...") Threading.Thread.Sleep(5 * 1000) End Sub Private Shared Sub client_DataChangeNotification_AllInObject(ByVal sender As Object, ByVal e As EasyUADataChangeNotificationEventArgs) ' Display value If e.Succeeded Then Console.WriteLine("{0}: {1}", e.Arguments.NodeDescriptor, e.AttributeData.Value) Else Console.WriteLine("{0} *** Failure: {1}", e.Arguments.NodeDescriptor, e.ErrorMessageBrief) End If End Sub End Class End Namespace
// This example shows how to store current state of the subscribed monitored items in a dictionary. // each change. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . using System; using System.Collections.Generic; using System.Threading; using OpcLabs.EasyOpc.UA; using OpcLabs.EasyOpc.UA.OperationModel; namespace UADocExamples._EasyUAClient { partial class SubscribeMultipleMonitoredItems { public static void StoreInDictionary() { 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 and hook events. using (var client = new EasyUAClient()) { client.DataChangeNotification += client_DataChangeNotification_StoreInDictionary; Console.WriteLine("Subscribing..."); client.SubscribeMultipleMonitoredItems(new[] { new EasyUAMonitoredItemArguments(null, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10845", 1000), new EasyUAMonitoredItemArguments(null, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000), new EasyUAMonitoredItemArguments(null, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10855", 1000) }); Console.WriteLine("Processing monitored item changed events for 1 minute..."); int startTickCount = Environment.TickCount; do { Thread.Sleep(5 * 1000); // Each 5 seconds, display the current state of the monitored items we have subscribed to. lock (_serialize) { Console.WriteLine(); foreach (KeyValuePair<UANodeDescriptor, UAAttributeDataResult> pair in _attributeDataResultDictionary) { UANodeDescriptor nodeDescriptor = pair.Key; UAAttributeDataResult attributeDataResult = pair.Value; Console.WriteLine($"{nodeDescriptor}: {attributeDataResult}"); } // The code above shows how you can process the complete contents of the dictionary. In other // scenarios, you may want to access just a specific entry in the dictionary. You can achieve that // by indexing the dictionary by the node descriptor of the monitored item you are interested in. } } while (Environment.TickCount < startTickCount + 60 * 1000); Console.WriteLine("Unsubscribing..."); } Console.WriteLine("Finished."); } static void client_DataChangeNotification_StoreInDictionary(object sender, EasyUADataChangeNotificationEventArgs e) { lock (_serialize) // Convert the event arguments to a UAAttributeData result object, and store it in the dictionary under the // key which is the node descriptor of the monitored item this data change notification is for. _attributeDataResultDictionary[e.Arguments.NodeDescriptor] = (UAAttributeDataResult)e; } // Holds last known state of each subscribed monitored item. private static readonly Dictionary<UANodeDescriptor, UAAttributeDataResult> _attributeDataResultDictionary = new Dictionary<UANodeDescriptor, UAAttributeDataResult>(); // Synchronization object used to prevent simultaneous access to the dictionary. private static readonly object _serialize = new object(); } }
# This example shows how to store current state of the subscribed monitored items in a dictionary. # 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 Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python . # The QuickOPC package is needed. Install it using "pip install opclabs_quickopc". import opclabs_quickopc import threading import time # Import .NET namespaces. from OpcLabs.EasyOpc.UA import * from OpcLabs.EasyOpc.UA.OperationModel import * lock = threading.Lock() attributeDataResultDictionary = {} # Data change notification event handler. def dataChangeNotification(sender, eventArgs): global lock global attributeDataResultDictionary with lock: # Convert the event arguments to a UAAttributeData result object, and store it in the dictionary under the # key which is the node descriptor of the monitored item this data change notification is for. attributeDataResultDictionary[eventArgs.Arguments.NodeDescriptor] = EasyUADataChangeNotificationEventArgs.ToUAAttributeDataResult(eventArgs) 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() # Hook events. client.DataChangeNotification += dataChangeNotification print('Subscribing...') client.SubscribeMultipleMonitoredItems([ EasyUAMonitoredItemArguments( None, endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10845'), UAMonitoringParameters(1000)), EasyUAMonitoredItemArguments( None, endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'), UAMonitoringParameters(1000)), EasyUAMonitoredItemArguments( None, endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10855'), UAMonitoringParameters(1000)), ]) print('Processing data change events for 1 minute...') endTime = time.time() + 60 while time.time() < endTime: time.sleep(5) # # Each 5 seconds, display the current state of the monitored items we have subscribed to. with lock: print() print('Current state of the monitored items:') for nodeDescriptor, attributeDataResult in attributeDataResultDictionary.items(): print(nodeDescriptor, ': ', attributeDataResult, sep='') # # The code above shows how you can process the complete contents of the dictionary. In other # scenarios, you may want to access just a specific entry in the dictionary. You can achieve that # by indexing the dictionary by the node descriptor of the monitored item you are interested in. print() print('Unsubscribing all monitored items...') client.UnsubscribeAllMonitoredItems() print('Waiting for 5 seconds...') time.sleep(5) print('Finished.')
' This example shows how to store current state of the subscribed monitored items in a dictionary. ' each change. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Imports System.Threading Imports OpcLabs.EasyOpc.UA Imports OpcLabs.EasyOpc.UA.OperationModel Namespace _EasyUAClient Partial Friend Class SubscribeMultipleMonitoredItems Public Shared Sub StoreInDictionary() ' Define which server we will work with. 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. Using client = New EasyUAClient() AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification_StoreInDictionary Console.WriteLine("Subscribing...") client.SubscribeMultipleMonitoredItems(New EasyUAMonitoredItemArguments() { New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10845", 1000), New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000), New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10855", 1000) }) Console.WriteLine("Processing monitored item changed events for 1 minute...") Dim startTickCount As Integer = Environment.TickCount Do Thread.Sleep(5 * 1000) ' Each 5 seconds, display the current state of the monitored items we have subscribed to. SyncLock _serialize Console.WriteLine() For Each pair As KeyValuePair(Of UANodeDescriptor, UAAttributeDataResult) In _attributeDataResultDictionary Dim nodeDescriptor As UANodeDescriptor = pair.Key Dim attributeDataResult As UAAttributeDataResult = pair.Value Console.WriteLine($"{nodeDescriptor}: {attributeDataResult}") Next ' The code above shows how you can process the complete contents of the dictionary. In other ' scenarios, you may want to access just a specific entry in the dictionary. You can achieve that ' by indexing the dictionary by the node descriptor of the monitored item you are interested in. End SyncLock Loop While Environment.TickCount < startTickCount + 60 * 1000 Console.WriteLine("Unsubscribing...") End Using Console.WriteLine("Finished.") End Sub Private Shared Sub client_DataChangeNotification_StoreInDictionary(ByVal sender As Object, ByVal e As EasyUADataChangeNotificationEventArgs) SyncLock _serialize ' Convert the event arguments to a UAAttributeData result object, and store it in the dictionary under the ' key which is the node descriptor of the monitored item this data change notification is for. _attributeDataResultDictionary(e.Arguments.NodeDescriptor) = CType(e, UAAttributeDataResult) End SyncLock ' Display value If e.Succeeded Then Console.WriteLine("{0}: {1}", e.Arguments.NodeDescriptor, e.AttributeData.Value) Else Console.WriteLine("{0} *** Failure: {1}", e.Arguments.NodeDescriptor, e.ErrorMessageBrief) End If End Sub ' Holds last known state of each subscribed monitores item. Private Shared ReadOnly _attributeDataResultDictionary As New Dictionary(Of UANodeDescriptor, UAAttributeDataResult) ' Synchronization object used to prevent simultaneous access to the dictionary. Private Shared ReadOnly _serialize As New Object End Class End Namespace
If you are only interested in certain kinds of changes in the monitored item, or need to reduce the amount of incoming notifications by specifying a deadband, use OPC UA Data Change Filter.
Note: It is NOT an error to subscribe to the same item twice (or more times), even with precisely same parameters. You will receive separate subscription handles, and with regard to your application, this situation will look no different from subscribing to different items. Internally, however, the subscription made to the OPC server might be optimized (merged together), depending on other parameters and circumstances.
OPC UA has one underlying mechanism for subscriptions, and the mechanism is further differentiated by the arguments used and the types of notifications generated. The general subscription mechanism refers to "monitored items", and in the current OPC UA version, the monitored item can represent two types of subscriptions: a subscription to either data changes, or events. The distinction is made by the type of filter specified with the subscription (in its monitoring parameters): It is either a data change filter, or an event filter. Depending on which type of subscription (filter) the monitored item uses, either data change notifications, or event notifications, are generated by the subscription.
Subscription methods that have "MonitoredItem" in their name are the most general ones. They allow you to create either data change or event subscriptions, depending on the data you pass in.
Subscription methods that have "DataChange" in their name are designed to create data change subscriptions only. Because of this specialization, they can have simplified set of arguments that makes most sense with data change subscriptions. These methods, however, do not do anything new as far as OPC UA subscriptions go: They just call the SubscribeMultipleMonitoredItems method internally, creating the generalized input arguments for it as needed.
Subscription methods that have "Event" in their name are designed to create event subscriptions only. Because of this specialization, they can have simplified set of arguments that makes most sense with event subscriptions. These methods, however, also do not do anything new as far as OPC UA subscriptions go: They just call the SubscribeMultipleMonitoredItems method internally, creating the generalized input arguments for it as needed.
You can use the more specialized methods if they provide the functionality you need, and give shorter code. In some cases, the more advanced functionality might be missing from the specialized methods, and in that case you should use the generalized methods and assemble the input arguments yourself.
The example below logs OPC Unified Architecture data changes into an XML file.
The main program:
// Logs OPC Unified Architecture data changes into an XML file. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . using System; using System.Diagnostics; using System.Xml; using System.Xml.Serialization; using OpcLabs.EasyOpc.UA; using OpcLabs.EasyOpc.UA.OperationModel; namespace UAXmlLogger { class Program { static void Main() { 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/" Console.WriteLine("Starting up..."); var xmlSerializer = new XmlSerializer(typeof(EasyUADataChangeNotificationEventArgs)); var xmlWriter = XmlWriter.Create("UAData.xml", new XmlWriterSettings { Indent = true, CloseOutput = true }); // The root element can have any name you need, but the name below also allows reading the log back as .NET array xmlWriter.WriteStartElement("ArrayOfEasyUADataChangeNotificationEventArgs"); Console.WriteLine("Logging data for 30 seconds..."); int handle = EasyUAClient.SharedInstance.SubscribeDataChange(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", samplingInterval:100, (_, eventArgs) => { Debug.Assert(!(eventArgs is null)); Console.Write("."); xmlSerializer.Serialize(xmlWriter, eventArgs); }); System.Threading.Thread.Sleep(30 * 1000); Console.WriteLine(); Console.WriteLine("Shutting down..."); EasyUAClient.SharedInstance.UnsubscribeMonitoredItem(handle); xmlWriter.WriteEndElement(); // not really necessary - XmlWriter would write the end tag for us anyway xmlWriter.Close(); Console.WriteLine("Finished."); } } }
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