'UsageDim instance As _EasyAEClient Dim handle As Integer instance.RefreshEventSubscription(handle)
| Exception | Description |
|---|---|
| System.ArgumentException | One of the arguments provided to a method is not valid. 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. |
When the client needs a refreshed list of active conditions, it will request a "refresh" from the server. The server will send event notifications to that specific client indicating that they are "refresh" instead of "original" event notifications. Since the client only needs to get the current state information for conditions, only condition events will be refreshed. Remark: "Refresh" is not a general "replay" capability since the server is not required to maintain an event history. Refresh is only for updating the client's state information for active or unacknowledged conditions.
In addition to the refresh indicator, there may be other differences between original and refresh event notifications. Specifically, since some attribute information available at the time of the original event notification may be unavailable at the time of the refresh, some attributes in the refresh may be null.
Refresh and original event notifications may be interleaved. Thus, it is the responsibility of the client to check time stamps on the event notifications and put them into the correct order, to ensure correct condition status is obtained.
When sending refresh event notifications, the server indicates if there are more refresh event notifications to send (see the RefreshComplete property of EasyAENotificationEventArgs).
This method is applicable to condition-related events only. Notifications for simple events and tracking events are not returned, even if they would satisfy the filter of the event subscription.
This method is applicable both when the subscription is active and when it is inactive (see the discussion of the Active for the SubscribeEvents and ChangeEventSubscription methods).
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.
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 . 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 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