Client and Subscriber Development > Development Models > Imperative Programming Model > Imperative Programming Model for OPC Classic A&E > Subscribing to Information (OPC A&E) > Refreshing Condition States (OPC A&E) |
Your application can obtain the current state of all conditions which are active, or which are inactive but unacknowledged, by requesting a “refresh” from an event subscription. The component will respond by sending the appropriate event notifications to the application, via the event handlers, for all conditions selected by the event subscription filter. When invoking the event handler, the component will indicate whether the invocation is for a refresh or is an original notification. Refresh and original event notifications will not be mixed in the same event notifications.
If you want to force a refresh, call the RefreshEventSubscription method, passing it the subscription handle.
// This example shows how to for a refresh for all active conditions and inactive, unacknowledged conditions. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . using System; using System.Threading; using OpcLabs.EasyOpc.AlarmsAndEvents; using OpcLabs.EasyOpc.AlarmsAndEvents.OperationModel; using OpcLabs.EasyOpc.DataAccess; using OpcLabs.EasyOpc.OperationModel; namespace DocExamples.AlarmsAndEvents._EasyAEClient { class RefreshEventSubscription { // Instantiate the OPC-A&E client object. static readonly EasyAEClient AEClient = new EasyAEClient(); // Instantiate the OPC-DA client object. static readonly EasyDAClient DAClient = new EasyDAClient(); public static void Main1() { var eventHandler = new EasyAENotificationEventHandler(AEClient_Notification); AEClient.Notification += eventHandler; Console.WriteLine("Processing event notifications..."); var subscriptionFilter = new AESubscriptionFilter { Sources = new AENodeDescriptor[] { "Simulation.ConditionState1", "Simulation.ConditionState2", "Simulation.ConditionState3" } }; int handle = AEClient.SubscribeEvents("", "OPCLabs.KitEventServer.2", 1000, null, subscriptionFilter); // The component will perform auto-refresh at this point, give it time to happen Console.WriteLine("Waiting for 10 seconds..."); Thread.Sleep(10 * 1000); // Set some events to active state, which will cause them to appear in refresh Console.WriteLine("Activating conditions and waiting for 10 seconds..."); try { DAClient.WriteItemValue("", "OPCLabs.KitServer.2", "SimulateEvents.ConditionState1.Activate", true); DAClient.WriteItemValue("", "OPCLabs.KitServer.2", "SimulateEvents.ConditionState2.Activate", true); } catch (OpcException opcException) { Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message); return; } Thread.Sleep(10 * 1000); Console.WriteLine("Refreshing subscription and waiting for 10 seconds..."); AEClient.RefreshEventSubscription(handle); Thread.Sleep(10 * 1000); AEClient.UnsubscribeEvents(handle); AEClient.Notification -= eventHandler; } // Notification event handler static void AEClient_Notification(object sender, EasyAENotificationEventArgs e) { Console.WriteLine(); if (!e.Succeeded) { Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief); return; } Console.WriteLine("Refresh: {0}", e.Refresh); Console.WriteLine("RefreshComplete: {0}", e.RefreshComplete); AEEventData eventData = e.EventData; if (!(eventData is null)) { Console.WriteLine("Event.QualifiedSourceName: {0}", eventData.QualifiedSourceName); Console.WriteLine("Event.Message: {0}", eventData.Message); Console.WriteLine("Event.Active: {0}", eventData.Active); Console.WriteLine("Event.Acknowledged: {0}", eventData.Acknowledged); } } } }
# This example shows how to for a refresh for all active conditions and inactive, unacknowledged conditions. # # 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 import * from OpcLabs.EasyOpc.AlarmsAndEvents import * from OpcLabs.EasyOpc.DataAccess import * from OpcLabs.EasyOpc.OperationModel import * # Notification event handler def notification(sender, e): if not e.Succeeded: print('*** Failure: ', e.ErrorMessageBrief, sep='') return print('Refresh: ', e.Refresh, sep='') print('RefreshComplete: ', e.RefreshComplete, sep='') eventData = e.EventData if eventData is not None: print('Event.QualifiedSourceName: ', eventData.QualifiedSourceName, sep='') print('Event.Message: ', eventData.Message, sep='') print('Event.Active: ', eventData.Active, sep='') print('Event.Acknowledged: ', eventData.Acknowledged, sep='') # Instantiate the OPC-A&E client object. aeClient = EasyAEClient() # Instantiate the OPC-DA client object. daClient = EasyDAClient() # aeClient.Notification += notification print('Processing event notifications...') subscriptionFilter = AESubscriptionFilter() subscriptionFilter.Sources = [ AENodeDescriptor('Simulation.ConditionState1'), AENodeDescriptor('Simulation.ConditionState2'), AENodeDescriptor('Simulation.ConditionState3'), ] handle = IEasyAEClientExtension.SubscribeEvents(aeClient, '', 'OPCLabs.KitEventServer.2', 1000, None, subscriptionFilter) # The component will perform auto-refresh at this point, give it time to happen. print('Waiting for 10 seconds...') time.sleep(10) # Set some events to active state, which will cause them to appear in refresh. print('Activating conditions and waiting for 10 seconds...') try: IEasyDAClientExtension.WriteItemValue(daClient, '', 'OPCLabs.KitServer.2', 'SimulateEvents.ConditionState1.Activate', True) IEasyDAClientExtension.WriteItemValue(daClient, '', 'OPCLabs.KitServer.2', 'SimulateEvents.ConditionState2.Activate', True) except OpcException as opcException: print('*** Failure: ' + opcException.GetBaseException().Message) exit() time.sleep(10) print('Refreshing event subscription and waiting for 10 seconds...') aeClient.RefreshEventSubscription(handle) time.sleep(10) aeClient.UnsubscribeEvents(handle) aeClient.Notification -= notification print('Finished.')
' This example shows how to for a refresh for all active conditions and inactive, unacknowledged conditions. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Imports System.Threading Imports OpcLabs.EasyOpc.AlarmsAndEvents Imports OpcLabs.EasyOpc.AlarmsAndEvents.OperationModel Imports OpcLabs.EasyOpc.DataAccess Imports OpcLabs.EasyOpc.OperationModel Namespace AlarmsAndEvents._EasyAEClient Friend Class RefreshEventSubscription _ Private Shared ReadOnly AEClient As New EasyAEClient() _ Private Shared ReadOnly DAClient As New EasyDAClient() Public Shared Sub Main1() Dim eventHandler = New EasyAENotificationEventHandler(AddressOf AEClient_Notification) AddHandler AEClient.Notification, eventHandler Console.WriteLine("Processing event notifications...") Dim subscriptionFilter As New AESubscriptionFilter subscriptionFilter.Sources = New AENodeDescriptor() {"Simulation.ConditionState1", "Simulation.ConditionState2", "Simulation.ConditionState3"} Dim handle As Integer = AEClient.SubscribeEvents("", "OPCLabs.KitEventServer.2", 1000, Nothing, subscriptionFilter) ' The component will perform auto-refresh at this point, give it time to happen Console.WriteLine("Waiting for 10 seconds...") Thread.Sleep(10 * 1000) ' Set some events to active state, which will cause them to appear in refresh Console.WriteLine("Activating conditions and waiting for 10 seconds...") Try DAClient.WriteItemValue("", "OPCLabs.KitServer.2", "SimulateEvents.ConditionState1.Activate", True) DAClient.WriteItemValue("", "OPCLabs.KitServer.2", "SimulateEvents.ConditionState2.Activate", True) Catch opcException As OpcException Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message) Exit Sub End Try Thread.Sleep(10 * 1000) Console.WriteLine("Refreshing subscription and waiting for 10 seconds...") AEClient.RefreshEventSubscription(handle) Thread.Sleep(10 * 1000) AEClient.UnsubscribeEvents(handle) RemoveHandler AEClient.Notification, eventHandler End Sub ' Notification event handler Private Shared Sub AEClient_Notification(ByVal sender As Object, ByVal e As EasyAENotificationEventArgs) Console.WriteLine() If Not e.Succeeded Then Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief) Exit Sub End If Console.WriteLine("Refresh: {0}", e.Refresh) Console.WriteLine("RefreshComplete: {0}", e.RefreshComplete) If e.EventData IsNot Nothing Then Dim eventData As AEEventData = e.EventData Console.WriteLine("Event.QualifiedSourceName: {0}", eventData.QualifiedSourceName) Console.WriteLine("Event.Message: {0}", eventData.Message) Console.WriteLine("Event.Active: {0}", eventData.Active) Console.WriteLine("Event.Acknowledged: {0}", eventData.Acknowledged) End If End Sub End Class End Namespace
Rem This example shows how to for a refresh for all active conditions and inactive, unacknowledged conditions. Rem Rem Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Option Explicit Dim DAClient: Set DAClient = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient") Dim AEClient: Set AEClient = CreateObject("OpcLabs.EasyOpc.AlarmsAndEvents.EasyAEClient") WScript.ConnectObject AEClient, "AEClient_" WScript.Echo "Processing event notifications..." Dim ServerDescriptor: Set ServerDescriptor = CreateObject("OpcLabs.EasyOpc.ServerDescriptor") ServerDescriptor.ServerClass = "OPCLabs.KitEventServer.2" Dim SourceDescriptor1: Set SourceDescriptor1 = CreateObject("OpcLabs.EasyOpc.AlarmsAndEvents.AENodeDescriptor") SourceDescriptor1.QualifiedName = "Simulation.ConditionState1" Dim SourceDescriptor2: Set SourceDescriptor2 = CreateObject("OpcLabs.EasyOpc.AlarmsAndEvents.AENodeDescriptor") SourceDescriptor2.QualifiedName = "Simulation.ConditionState1" Dim SourceDescriptor3: Set SourceDescriptor3 = CreateObject("OpcLabs.EasyOpc.AlarmsAndEvents.AENodeDescriptor") SourceDescriptor3.QualifiedName = "Simulation.ConditionState1" Dim SubscriptionParameters: Set SubscriptionParameters = CreateObject("OpcLabs.EasyOpc.AlarmsAndEvents.AESubscriptionParameters") SubscriptionParameters.Filter.Sources = Array(SourceDescriptor1, SourceDescriptor2, SourceDescriptor3) SubscriptionParameters.NotificationRate = 1000 Dim handle: handle = AEClient.SubscribeEvents(ServerDescriptor, SubscriptionParameters, True, Nothing) Rem The component will perform auto-refresh at this point, give it time to happen WScript.Echo "Waiting for 10 seconds..." WScript.Sleep 10*1000 Rem Set some events to active state, which will cause them to appear in refresh On Error Resume Next WScript.Echo "Activating conditions and waiting for 10 seconds..." DAClient.WriteItemValue "", "OPCLabs.KitServer.2", "SimulateEvents.ConditionState1.Activate", True DAClient.WriteItemValue "", "OPCLabs.KitServer.2", "SimulateEvents.ConditionState2.Activate", True If Err.Number <> 0 Then WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description WScript.Quit End If On Error Goto 0 WScript.Sleep 10*1000 WScript.Echo "Refreshing subscription and waiting for 10 seconds..." AEClient.RefreshEventSubscription handle WScript.Sleep 10*1000 AEClient.UnsubscribeEvents handle Rem Notification event handler Sub AEClient_Notification(Sender, e) If Not (e.Succeeded) Then WScript.Echo "*** Failure: " & e.ErrorMessageBrief Exit Sub End If WScript.Echo WScript.Echo "Refresh: " & e.Refresh WScript.Echo "RefreshComplete: " & e.RefreshComplete If Not (e.EventData Is Nothing) Then With e.EventData WScript.Echo "EventData.QualifiedSourceName: " & .QualifiedSourceName WScript.Echo "EventData.Message: " & .Message WScript.Echo "EventData.Active: " & .Active WScript.Echo "EventData.Acknowledged: " & .Acknowledged End With End If End Sub
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