OPC Studio User's Guide and Reference
Subscribing to OPC UA Events
Concepts > OPC Data Client Concepts > OPC Data Client Development Models > Imperative Programming Model > Imperative Programming Model for OPC UA Alarms & Conditions > Subscribing to Information (OPC UA Alarms & Conditions) > Subscribing to OPC UA Events
In This Topic

General

Generally speaking, you subscribe to OPC UA Events similarly to data changes, but by using monitoring parameters that contain an event filter instead of data change filter. Besides the UAMonitoringParameters.DataChangeFilter property, the UAMonitoringParameters class also has an EventFilter property (of UAEventFilter type). The developer can specify either a data change filter, or an event filter, with monitoring parameters.

As the UAMonitoringParameters are part of the information that gets passed (directly or indirectly) to any EasyUAClient.SubscribeMonitoredItem or SubscribeMultipleMonitoredItems call, the introduction of the EventFilter property and the EventNotification event (both described above) are, in fact, the only core features that already in itself allow the Alarms & Conditions support to work. Many other features simply provide better developer experience above this.

A single event

Instead of putting together the monitoring parameters with an event filter, you can subscribe to events a bit easier using the IEasyUAClient.SubscribeEvent extension method, with several overloads. Similarly to the IEasyUAClient.SubscribeDataChange extension method (for data changes), the SubscribeEvent method provides a simplified way to subscribe to events.

.NET

// This example shows how to subscribe to event notifications and display each incoming event.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// 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.

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

namespace UADocExamples.AlarmsAndConditions
{
    partial class SubscribeEvent
    {
        public static void Overload1()
        {
            // Define which server we will work with.
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

            // Instantiate the client object and hook events.
            var client = new EasyUAClient();
            client.EventNotification += client_EventNotification;

            Console.WriteLine("Subscribing...");
            client.SubscribeEvent(endpointDescriptor, UAObjectIds.Server, 1000);

            Console.WriteLine("Processing event notifications for 30 seconds...");
            System.Threading.Thread.Sleep(30 * 1000);

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

            Console.WriteLine("Waiting for 5 seconds...");
            System.Threading.Thread.Sleep(5 * 1000);

            Console.WriteLine("Finished.");
        }

        static void client_EventNotification(object sender, EasyUAEventNotificationEventArgs e)
        {
            // Display the event.
            Console.WriteLine(e);
        }



        // Example output (truncated):
        //Subscribing...
        //Processing event notifications for 30 seconds...
        //[] Success
        //[] Success; Refresh; RefreshInitiated
        //[] Success; Refresh; [EastTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
        //[] Success; Refresh; [EastTank] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
        //[] Success; Refresh; [EastTank] 500! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
        //[] Success; Refresh; [EastTank] 900! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
        //[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:03 PM (10 fields)
        //[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:03 PM (10 fields)
        //[] Success; Refresh; [NorthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
        //[] Success; Refresh; [NorthMotor] 500! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
        //[] Success; Refresh; [NorthMotor] 900! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
        //[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
        //[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:08 PM (10 fields)
        //[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:14 PM (10 fields)
        //[] Success; Refresh; [WestTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
        //[] Success; Refresh; [WestTank] 900! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
        //[] Success; Refresh; [WestTank] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
        //[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
        //[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:55 PM (10 fields)
        //[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:43 PM (10 fields)
        //[] Success; Refresh; [SouthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
        //[] Success; Refresh; [SouthMotor] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
        //[] Success; Refresh; [SouthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
        //[] Success; Refresh; [SouthMotor] 500! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
        //[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:51 PM (10 fields)
        //[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:57 PM (10 fields)
        //[] Success; Refresh; RefreshComplete
        //[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:39 PM (10 fields)
        //[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:39 PM (10 fields)
        //[] Success; [EastTank] 100! {TripAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
        //[] Success; [NorthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
        //[] Success; [WestTank] 100! {ExclusiveDeviationAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
        //[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:40 PM (10 fields)
        //[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:40 PM (10 fields)
        //[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:41 PM (10 fields)
        //[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:41 PM (10 fields)
        //[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:42 PM (10 fields)
        //[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:42 PM (10 fields)
        //[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:43 PM (10 fields)
        //[] Success; [NorthMotor] 300! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
        //[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:43 PM (10 fields)
        //[] Success; [WestTank] 300! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
        //[] Success; [SouthMotor] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
        //[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:44 PM (10 fields)
        //[] Success; [EastTank] 700! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
        //[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:44 PM (10 fields)
        //[] Success; [NorthMotor] 700! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
        //[] Success; [SouthMotor] 700! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
        //[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:45 PM (10 fields)
        //[] Success; [EastTank] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:45 PM (10 fields)
        //[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:45 PM (10 fields)
        //...
    }
}

# This example shows how to subscribe to event notifications and display each incoming event.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in PowerShell on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PowerShell .
# 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.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.UA
using namespace OpcLabs.EasyOpc.UA.AddressSpace
using namespace OpcLabs.EasyOpc.UA.AddressSpace.Standard

# 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"

# Define which server we will work with.
[UAEndpointDescriptor]$endpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"

# Instantiate the client object.
$client = New-Object EasyUAClient

# Event notification handler
Register-ObjectEvent -InputObject $client -EventName EventNotification -Action { 
    # Display the event.
    Write-Host $EventArgs
}

Write-Host "Subscribing..."
[IEasyUAClientExtension]::SubscribeEvent($client, $endpointDescriptor, [UAObjectIds]::Server, 1000)

Write-Host "Processing event notifications for 30 seconds..."
$stopwatch =  [System.Diagnostics.Stopwatch]::StartNew() 
while ($stopwatch.Elapsed.TotalSeconds -lt 30) {    
    Start-Sleep -Seconds 1
}

Write-Host "Unsubscribing..."
$client.UnsubscribeAllMonitoredItems()

Write-Host "Waiting for 5 seconds..."
Start-Sleep -Seconds 5

Write-Host "Finished."


# Example output (truncated):
#Subscribing...
#Processing event notifications for 30 seconds...
#[] Success
#[] Success; Refresh; RefreshInitiated
#[] Success; Refresh; [EastTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
#[] Success; Refresh; [EastTank] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
#[] Success; Refresh; [EastTank] 500! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
#[] Success; Refresh; [EastTank] 900! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
#[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:03 PM (10 fields)
#[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:03 PM (10 fields)
#[] Success; Refresh; [NorthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
#[] Success; Refresh; [NorthMotor] 500! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
#[] Success; Refresh; [NorthMotor] 900! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
#[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
#[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:08 PM (10 fields)
#[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:14 PM (10 fields)
#[] Success; Refresh; [WestTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
#[] Success; Refresh; [WestTank] 900! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
#[] Success; Refresh; [WestTank] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
#[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
#[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:55 PM (10 fields)
#[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:43 PM (10 fields)
#[] Success; Refresh; [SouthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
#[] Success; Refresh; [SouthMotor] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
#[] Success; Refresh; [SouthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
#[] Success; Refresh; [SouthMotor] 500! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
#[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:51 PM (10 fields)
#[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:57 PM (10 fields)
#[] Success; Refresh; RefreshComplete
#[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:39 PM (10 fields)
#[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:39 PM (10 fields)
#[] Success; [EastTank] 100! {TripAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
#[] Success; [NorthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
#[] Success; [WestTank] 100! {ExclusiveDeviationAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
#[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:40 PM (10 fields)
#[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:40 PM (10 fields)
#[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:41 PM (10 fields)
#[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:41 PM (10 fields)
#[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:42 PM (10 fields)
#[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:42 PM (10 fields)
#[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:43 PM (10 fields)
#[] Success; [NorthMotor] 300! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
#[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:43 PM (10 fields)
#[] Success; [WestTank] 300! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
#[] Success; [SouthMotor] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
#[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:44 PM (10 fields)
#[] Success; [EastTank] 700! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
#[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:44 PM (10 fields)
#[] Success; [NorthMotor] 700! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
#[] Success; [SouthMotor] 700! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
#[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:45 PM (10 fields)
#[] Success; [EastTank] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:45 PM (10 fields)
#[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:45 PM (10 fields)
#...


' This example shows how to subscribe to event notifications and display each incoming event.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.AddressSpace.Standard
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace AlarmsAndConditions
    Friend Class SubscribeEvent
        Public Shared Sub Overload1()
            ' Instantiate the client object and hook events
            Dim client = New EasyUAClient()
            AddHandler client.EventNotification, AddressOf client_EventNotification

            Console.WriteLine("Subscribing...")
            client.SubscribeEvent( _
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer", _
                UAObjectIds.Server, _
                1000)

            Console.WriteLine("Processing event notifications 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_EventNotification(ByVal sender As Object, ByVal e As EasyUAEventNotificationEventArgs)
            ' Display the event
            Console.WriteLine(e)
        End Sub



        ' Example output (truncated):
        'Subscribing...
        'Processing event notifications for 30 seconds...
        '[] Success
        '[] Success; Refresh; RefreshInitiated
        '[] Success; Refresh; [EastTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
        '[] Success; Refresh; [EastTank] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
        '[] Success; Refresh; [EastTank] 500! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
        '[] Success; Refresh; [EastTank] 900! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
        '[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:03 PM (10 fields)
        '[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:03 PM (10 fields)
        '[] Success; Refresh; [NorthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
        '[] Success; Refresh; [NorthMotor] 500! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
        '[] Success; Refresh; [NorthMotor] 900! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
        '[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
        '[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:08 PM (10 fields)
        '[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:14 PM (10 fields)
        '[] Success; Refresh; [WestTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
        '[] Success; Refresh; [WestTank] 900! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
        '[] Success; Refresh; [WestTank] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
        '[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
        '[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:55 PM (10 fields)
        '[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:43 PM (10 fields)
        '[] Success; Refresh; [SouthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
        '[] Success; Refresh; [SouthMotor] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
        '[] Success; Refresh; [SouthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
        '[] Success; Refresh; [SouthMotor] 500! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
        '[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:51 PM (10 fields)
        '[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:57 PM (10 fields)
        '[] Success; Refresh; RefreshComplete
        '[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:39 PM (10 fields)
        '[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:39 PM (10 fields)
        '[] Success; [EastTank] 100! {TripAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
        '[] Success; [NorthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
        '[] Success; [WestTank] 100! {ExclusiveDeviationAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
        '[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:40 PM (10 fields)
        '[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:40 PM (10 fields)
        '[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:41 PM (10 fields)
        '[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:41 PM (10 fields)
        '[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:42 PM (10 fields)
        '[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:42 PM (10 fields)
        '[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:43 PM (10 fields)
        '[] Success; [NorthMotor] 300! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
        '[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:43 PM (10 fields)
        '[] Success; [WestTank] 300! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
        '[] Success; [SouthMotor] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
        '[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:44 PM (10 fields)
        '[] Success; [EastTank] 700! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
        '[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:44 PM (10 fields)
        '[] Success; [NorthMotor] 700! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
        '[] Success; [SouthMotor] 700! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
        '[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:45 PM (10 fields)
        '[] Success; [EastTank] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:45 PM (10 fields)
        '[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:45 PM (10 fields)
        '...

    End Class
End Namespace

COM

// This example shows how to subscribe to event notifications and display each incoming event.
//
// 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.

type
  TClientEventHandlers18 = class
    procedure Client_EventNotification(
      ASender: TObject;
      sender: OleVariant;
      const eventArgs: _EasyUAEventNotificationEventArgs);
  end;

procedure TClientEventHandlers18.Client_EventNotification(
  ASender: TObject;
  sender: OleVariant;
  const eventArgs: _EasyUAEventNotificationEventArgs);
begin
  // Display the event
  if eventArgs.Succeeded then
    WriteLn(eventArgs.ToString)
  else
    WriteLn(Format('*** Failure: %s', [eventArgs.ErrorMessageBrief]));
end;

class procedure SubscribeEvent.Main;
const
  UAObjectIds_Server = 'nsu=http://opcfoundation.org/UA/;i=2253';
var
  Client: TEasyUAClient;
  ClientEventHandlers: TClientEventHandlers18;
  EndpointDescriptor: string;
begin
  EndpointDescriptor := 'opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer';

  // Instantiate the client object and hook events
  Client := TEasyUAClient.Create(nil);
  ClientEventHandlers := TClientEventHandlers18.Create;
  Client.OnEventNotification := ClientEventHandlers.Client_EventNotification;

  WriteLn('Subscribing...');
  Client.SubscribeEvent(EndpointDescriptor, UAObjectIds_Server, 1000);

  WriteLn('Processing event notifications for 30 seconds...');
  PumpSleep(30*1000);

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

  WriteLn('Waiting for 5 seconds...');
  Sleep(5*1000);

  WriteLn('Finished.');
  FreeAndNil(Client);
  FreeAndNil(ClientEventHandlers);

end;



// Example output (truncated):
//Subscribing...
//Processing event notifications for 30 seconds...
//[] Success
//[] Success; Refresh; RefreshInitiated
//[] Success; Refresh; [EastTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
//[] Success; Refresh; [EastTank] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
//[] Success; Refresh; [EastTank] 500! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
//[] Success; Refresh; [EastTank] 900! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
//[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:03 PM (10 fields)
//[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:03 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 500! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 900! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:08 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:14 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
//[] Success; Refresh; [WestTank] 900! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:55 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:43 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 500! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:51 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:57 PM (10 fields)
//[] Success; Refresh; RefreshComplete
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [EastTank] 100! {TripAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [NorthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [WestTank] 100! {ExclusiveDeviationAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:40 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:40 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:41 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:41 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:42 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:42 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [NorthMotor] 300! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [WestTank] 300! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [SouthMotor] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [EastTank] 700! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [NorthMotor] 700! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [SouthMotor] 700! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:45 PM (10 fields)
//[] Success; [EastTank] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:45 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:45 PM (10 fields)
//...


// This example shows how to subscribe to event notifications and display each incoming event.
//
// 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.


class ClientEvents {
    function EventNotification($Sender, $E)
    {
        // Display the event
        if ($E->Succeeded) {
            printf("%s\n", $E);
        }
        else {
            printf(" *** Failure: %s\n", $E->ErrorMessageBrief);
        }
    }
}

const UAObjectIds_Server = "nsu=http://opcfoundation.org/UA/;i=2253";

$EndpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

// 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");
$Client->SubscribeEvent($EndpointDescriptor, UAObjectIds_Server, 1000);

printf("Processing event notifications for 30 seconds...\n");
$startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 30);

printf("Unsubscribing...\n");
$Client->UnsubscribeAllMonitoredItems;

printf("Waiting for 5 seconds...\n");
$startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 5);



// Example output (truncated):
//Subscribing...
//Processing event notifications for 30 seconds...
//[] Success
//[] Success; Refresh; RefreshInitiated
//[] Success; Refresh; [EastTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
//[] Success; Refresh; [EastTank] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
//[] Success; Refresh; [EastTank] 500! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
//[] Success; Refresh; [EastTank] 900! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
//[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:03 PM (10 fields)
//[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:03 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 500! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 900! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:08 PM (10 fields)
//[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:14 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
//[] Success; Refresh; [WestTank] 900! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:55 PM (10 fields)
//[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:43 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 500! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:51 PM (10 fields)
//[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:57 PM (10 fields)
//[] Success; Refresh; RefreshComplete
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [EastTank] 100! {TripAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [NorthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [WestTank] 100! {ExclusiveDeviationAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:40 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:40 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:41 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:41 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:42 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:42 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [NorthMotor] 300! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [WestTank] 300! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [SouthMotor] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [EastTank] 700! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [NorthMotor] 700! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [SouthMotor] 700! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
//[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:45 PM (10 fields)
//[] Success; [EastTank] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:45 PM (10 fields)
//[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:45 PM (10 fields)
//...


REM This example shows how to subscribe to event notifications and display each incoming event.
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.

Private Sub SubscribeEvent_Main_Command_Click()
    OutputText = ""
    
    Const UAObjectIds_Server = "nsu=http://opcfoundation.org/UA/;i=2253"
    
    Dim endpointDescriptor As String
    endpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"
    
    ' Instantiate the client object and hook events
    Set Client1 = New EasyUAClient

    OutputText = OutputText & "Subscribing..." & vbCrLf
    Call Client1.SubscribeEvent(endpointDescriptor, UAObjectIds_Server, 1000)

    OutputText = OutputText & "Processing event notifications for 30 seconds..." & vbCrLf
    Pause 30000

    OutputText = OutputText & "Unsubscribing..." & vbCrLf
    Client1.UnsubscribeAllMonitoredItems

    OutputText = OutputText & "Waiting for 5 seconds..." & vbCrLf
    Pause 5000

    OutputText = OutputText & "Finished." & vbCrLf

    Set Client1 = Nothing
End Sub

Private Sub Client1_EventNotification(ByVal sender As Variant, ByVal eventArgs As EasyUAEventNotificationEventArgs)
    ' Display the event
    If eventArgs.Succeeded Then
        OutputText = OutputText & eventArgs & vbCrLf
    Else
        OutputText = OutputText & eventArgs.ErrorMessageBrief & vbCrLf
    End If
End Sub

Rem This example shows how to subscribe to event notifications and display each incoming event.
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

Const uaObjectIds_Server = "nsu=http://opcfoundation.org/UA/;i=2253"

' Instantiate the client object and hook events
Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient")
WScript.ConnectObject Client, "Client_"

WScript.Echo "Subscribing..."
Client.SubscribeEvent "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer", uaObjectIds_Server, 1000

WScript.Echo "Processing event notifications for 30 seconds..."
WScript.Sleep 30*1000



Sub Client_EventNotification(Sender, e)
    ' Display the event
    WScript.Echo e
End Sub



' Example output (truncated):
'Subscribing...
'Processing event notifications for 30 seconds...
'[] Success
'[] Success; Refresh; RefreshInitiated
'[] Success; Refresh; [EastTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
'[] Success; Refresh; [EastTank] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
'[] Success; Refresh; [EastTank] 500! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
'[] Success; Refresh; [EastTank] 900! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
'[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:03 PM (10 fields)
'[] Success; Refresh; [EastTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:03 PM (10 fields)
'[] Success; Refresh; [NorthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
'[] Success; Refresh; [NorthMotor] 500! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
'[] Success; Refresh; [NorthMotor] 900! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
'[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
'[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:08 PM (10 fields)
'[] Success; Refresh; [NorthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:40:14 PM (10 fields)
'[] Success; Refresh; [WestTank] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
'[] Success; Refresh; [WestTank] 900! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:29 PM (10 fields)
'[] Success; Refresh; [WestTank] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
'[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
'[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:55 PM (10 fields)
'[] Success; Refresh; [WestTank] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:43 PM (10 fields)
'[] Success; Refresh; [SouthMotor] 100! {DialogConditionType} "The dialog was activated" @9/9/2021 2:22:18 PM (10 fields)
'[] Success; Refresh; [SouthMotor] 100! {ExclusiveDeviationAlarmType} "The alarm is active." @9/9/2021 4:19:32 PM (10 fields)
'[] Success; Refresh; [SouthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm is active." @9/9/2021 4:19:37 PM (10 fields)
'[] Success; Refresh; [SouthMotor] 500! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:35 PM (10 fields)
'[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:39:51 PM (10 fields)
'[] Success; Refresh; [SouthMotor] 100! {TripAlarmType} "The alarm severity has increased." @9/9/2021 3:38:57 PM (10 fields)
'[] Success; Refresh; RefreshComplete
'[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:39 PM (10 fields)
'[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:39 PM (10 fields)
'[] Success; [EastTank] 100! {TripAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
'[] Success; [NorthMotor] 100! {NonExclusiveLevelAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
'[] Success; [WestTank] 100! {ExclusiveDeviationAlarmType} "The alarm was deactivated by the system." @9/9/2021 4:19:39 PM (10 fields)
'[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:40 PM (10 fields)
'[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:40 PM (10 fields)
'[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:41 PM (10 fields)
'[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:41 PM (10 fields)
'[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:42 PM (10 fields)
'[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:42 PM (10 fields)
'[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:43 PM (10 fields)
'[] Success; [NorthMotor] 300! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
'[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:43 PM (10 fields)
'[] Success; [WestTank] 300! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
'[] Success; [SouthMotor] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:43 PM (10 fields)
'[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:44 PM (10 fields)
'[] Success; [EastTank] 700! {NonExclusiveLevelAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
'[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:44 PM (10 fields)
'[] Success; [NorthMotor] 700! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
'[] Success; [SouthMotor] 700! {TripAlarmType} "The alarm severity has increased." @9/9/2021 4:19:44 PM (10 fields)
'[] Success; [Internal] 500! {SystemEventType} "Raising Events" @9/9/2021 4:19:45 PM (10 fields)
'[] Success; [EastTank] 300! {ExclusiveDeviationAlarmType} "The alarm severity has increased." @9/9/2021 4:19:45 PM (10 fields)
'[] Success; [Internal] 500! {AuditEventType} "Events Raised" @9/9/2021 4:19:45 PM (10 fields)
'...

Python

# This example shows how to subscribe to event notifications and display each incoming event.
#
# 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 .
# 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.
# 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.AddressSpace.Standard import *
from OpcLabs.EasyOpc.UA.OperationModel import *


def eventNotification(sender, eventArgs):
    # Display the event.
    print(eventArgs)


# Define which server we will work with.
endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer')

# Instantiate the client object and hook events.
client = EasyUAClient()
client.EventNotification += eventNotification

print('Subscribing...')
IEasyUAClientExtension.SubscribeEvent(
    client,
    endpointDescriptor,
    UANodeDescriptor(UAObjectIds.Server),
    1000)

print('Processing event notifications for 30 seconds...')
time.sleep(30)

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

print('Waiting for 5 seconds...')
time.sleep(5)

print('Finished.')

 

Multiple events

Multiple events are more efficiently subscribed using the SubscribeMultipleMonitoredItems method:

.NET

// This example shows how to subscribe to multiple events.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// 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.

using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.AddressSpace;
using OpcLabs.EasyOpc.UA.AddressSpace.Standard;
using OpcLabs.EasyOpc.UA.AlarmsAndConditions;
using OpcLabs.EasyOpc.UA.Filtering;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.AlarmsAndConditions
{
    class SubscribeMultipleMonitoredItems
    {
        public static void Events()
        {
            // Define which server we will work with.
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

            // Instantiate the client object and hook events.
            var client = new EasyUAClient();
            client.EventNotification += client_EventNotification;

            Console.WriteLine("Subscribing...");
            client.SubscribeMultipleMonitoredItems(new[]
                {
                    new EasyUAMonitoredItemArguments("firstState", 
                        endpointDescriptor, 
                        UAObjectIds.Server,
                        new UAMonitoringParameters(1000, new UAEventFilterBuilder(
                            UAFilterElements.GreaterThanOrEqual(UABaseEventObject.Operands.Severity, 500),
                            UABaseEventObject.AllFields)))
                        { AttributeId = UAAttributeId.EventNotifier },
                    new EasyUAMonitoredItemArguments("secondState",
                        endpointDescriptor, 
                        UAObjectIds.Server,
                        new UAMonitoringParameters(2000, new UAEventFilterBuilder(
                            UAFilterElements.Equals(
                                UABaseEventObject.Operands.SourceNode, 
                                new UANodeId("nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=1:Metals/SouthMotor")),
                            UABaseEventObject.AllFields)))
                        { AttributeId = UAAttributeId.EventNotifier }
                });

            Console.WriteLine("Processing event notifications for 30 seconds...");
            System.Threading.Thread.Sleep(30 * 1000);

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

            Console.WriteLine("Waiting for 5 seconds...");
            System.Threading.Thread.Sleep(5 * 1000);

            Console.WriteLine("Finished.");
        }

        static void client_EventNotification(object sender, EasyUAEventNotificationEventArgs e)
        {
            // Display the event
            Console.WriteLine(e);
        }
        

        // Example output (truncated):
        //Subscribing...
        //Processing monitored item changed events for 30 seconds...
        //[firstState] Success
        //[secondState] Success
        //[firstState] Success; Refresh; RefreshInitiated
        //[firstState] Success; Refresh; (10 field results) [EastTank] 500! "The alarm was acknoweledged." @10/14/2019 4:00:13 PM
        //[firstState] Success; Refresh; (10 field results) [EastTank] 500! "The alarm was acknoweledged." @10/14/2019 4:00:17 PM
        //[firstState] Success; Refresh; (10 field results) [NorthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:02 PM
        //[firstState] Success; Refresh; (10 field results) [NorthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:16 PM
        //[firstState] Success; Refresh; (10 field results) [SouthMotor] 700! "The alarm was acknoweledged." @10/14/2019 4:00:21 PM
        //[firstState] Success; Refresh; (10 field results) [SouthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:03 PM
        //[firstState] Success; Refresh; RefreshComplete
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:08 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:08 PM
        //[secondState] Success; Refresh; RefreshInitiated
        //[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The dialog was activated" @9/10/2019 8:08:25 PM
        //[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm is active." @11/8/2019 7:48:07 PM
        //[secondState] Success; Refresh; (10 field results) [SouthMotor] 700! "The alarm was acknoweledged." @10/14/2019 4:00:21 PM
        //[secondState] Success; Refresh; (10 field results) [SouthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:03 PM
        //[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm severity has increased." @9/10/2019 8:09:02 PM
        //[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm severity has increased." @9/10/2019 8:09:59 PM
        //[secondState] Success; Refresh; RefreshComplete
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:09 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:09 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:10 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:10 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:11 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:11 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:12 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:12 PM
        //[firstState] Success; (10 field results) [EastTank] 500! "The alarm severity has increased." @11/8/2019 7:48:13 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:13 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:13 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:14 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:14 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:15 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:15 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:16 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:16 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:17 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:17 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:18 PM
        //[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:18 PM
        //[secondState] Success; (10 field results) [SouthMotor] 300! "The alarm severity has increased." @11/8/2019 7:48:18 PM
        //...
    }
}

# This example shows how to subscribe to multiple events.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in PowerShell on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PowerShell .
# 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.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.UA
using namespace OpcLabs.EasyOpc.UA.AddressSpace
using namespace OpcLabs.EasyOpc.UA.AddressSpace.Standard
using namespace OpcLabs.EasyOpc.UA.AlarmsAndConditions
using namespace OpcLabs.EasyOpc.UA.Filtering
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"

# Define which server we will work with.
[UAEndpointDescriptor]$endpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"

# Instantiate the client object.
$client = New-Object EasyUAClient

# Event notification handler
Register-ObjectEvent -InputObject $client -EventName EventNotification -Action { 
    # Display the event.
    Write-Host $EventArgs
}

Write-Host "Subscribing..."
$client.SubscribeMultipleMonitoredItems(@(
        (New-Object EasyUAMonitoredItemArguments("firstState",
            $endpointDescriptor, 
            [UAObjectIds]::Server,
            (New-Object UAMonitoringParameters(1000, [UAEventFilter](New-Object UAEventFilterBuilder(
                [UAFilterElements]::GreaterThanOrEqual([UABaseEventObject+Operands]::Severity, 500),
                [UABaseEventObject]::AllFields))))) `
            -Property @{ AttributeId = [UAAttributeId]::EventNotifier }),
        (New-Object EasyUAMonitoredItemArguments("secondState",
            $endpointDescriptor, 
            [UAObjectIds]::Server,
            (New-Object UAMonitoringParameters(2000, [UAEventFilter](New-Object UAEventFilterBuilder(
                [UAFilterElements]::Equals(
                    [UABaseEventObject+Operands]::SourceNode, 
                    (New-Object UANodeId("nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=1:Metals/SouthMotor"))),
                [UABaseEventObject]::AllFields))))) `
            -Property @{ AttributeId = [UAAttributeId]::EventNotifier })
    ))

Write-Host "Processing event notifications for 30 seconds..."
$stopwatch =  [System.Diagnostics.Stopwatch]::StartNew() 
while ($stopwatch.Elapsed.TotalSeconds -lt 30) {    
    Start-Sleep -Seconds 1
}

Write-Host "Unsubscribing..."
$client.UnsubscribeAllMonitoredItems()

Write-Host "Waiting for 5 seconds..."
Start-Sleep -Seconds 5

Write-Host "Finished."
      

# Example output (truncated):
#Subscribing...
#Processing monitored item changed events for 30 seconds...
#[firstState] Success
#[secondState] Success
#[firstState] Success; Refresh; RefreshInitiated
#[firstState] Success; Refresh; (10 field results) [EastTank] 500! "The alarm was acknoweledged." @10/14/2019 4:00:13 PM
#[firstState] Success; Refresh; (10 field results) [EastTank] 500! "The alarm was acknoweledged." @10/14/2019 4:00:17 PM
#[firstState] Success; Refresh; (10 field results) [NorthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:02 PM
#[firstState] Success; Refresh; (10 field results) [NorthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:16 PM
#[firstState] Success; Refresh; (10 field results) [SouthMotor] 700! "The alarm was acknoweledged." @10/14/2019 4:00:21 PM
#[firstState] Success; Refresh; (10 field results) [SouthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:03 PM
#[firstState] Success; Refresh; RefreshComplete
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:08 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:08 PM
#[secondState] Success; Refresh; RefreshInitiated
#[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The dialog was activated" @9/10/2019 8:08:25 PM
#[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm is active." @11/8/2019 7:48:07 PM
#[secondState] Success; Refresh; (10 field results) [SouthMotor] 700! "The alarm was acknoweledged." @10/14/2019 4:00:21 PM
#[secondState] Success; Refresh; (10 field results) [SouthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:03 PM
#[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm severity has increased." @9/10/2019 8:09:02 PM
#[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm severity has increased." @9/10/2019 8:09:59 PM
#[secondState] Success; Refresh; RefreshComplete
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:09 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:09 PM
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:10 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:10 PM
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:11 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:11 PM
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:12 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:12 PM
#[firstState] Success; (10 field results) [EastTank] 500! "The alarm severity has increased." @11/8/2019 7:48:13 PM
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:13 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:13 PM
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:14 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:14 PM
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:15 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:15 PM
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:16 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:16 PM
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:17 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:17 PM
#[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:18 PM
#[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:18 PM
#[secondState] Success; (10 field results) [SouthMotor] 300! "The alarm severity has increased." @11/8/2019 7:48:18 PM
#...


' This example shows how to subscribe to multiple events.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.AddressSpace
Imports OpcLabs.EasyOpc.UA.AddressSpace.Standard
Imports OpcLabs.EasyOpc.UA.AlarmsAndConditions
Imports OpcLabs.EasyOpc.UA.Filtering
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace AlarmsAndConditions
    Partial Friend Class SubscribeMultipleMonitoredItems
        Public Shared Sub Events()

            ' Instantiate the client object and hook events
            Dim client = New EasyUAClient()
            AddHandler client.EventNotification, AddressOf client_EventNotification

            Console.WriteLine("Subscribing...")

            client.SubscribeMultipleMonitoredItems(New EasyUAMonitoredItemArguments() _
                { _
                    New EasyUAMonitoredItemArguments("firstState", _
                        "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer", _
                        UAObjectIds.Server, _
                        New UAMonitoringParameters(1000, New UAEventFilterBuilder( _
                            UAFilterElements.GreaterThanOrEqual(UABaseEventObject.Operands.Severity, 500), _
                            UABaseEventObject.AllFields))) _
                        With {.AttributeId = UAAttributeId.EventNotifier}, _
                    New EasyUAMonitoredItemArguments("secondState", _
                        "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer", _
                        UAObjectIds.Server, _
                        New UAMonitoringParameters(2000, New UAEventFilterBuilder( _
                            UAFilterElements.Equals( _
                                UABaseEventObject.Operands.SourceNode, _
                                New UANodeId("nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=1:Metals/SouthMotor")), _
                            UABaseEventObject.AllFields))) _
                        With {.AttributeId = UAAttributeId.EventNotifier} _
                } _
             )

            Console.WriteLine("Processing event notifications for 30 seconds...")
            Threading.Thread.Sleep(30 * 1000)

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

            Console.WriteLine("Waiting for 5 seconds...")
            Threading.Thread.Sleep(5 * 1000)
        End Sub

        Private Shared Sub client_EventNotification(ByVal sender As Object, ByVal e As EasyUAEventNotificationEventArgs)
            ' Display the event
            Console.WriteLine(e)
        End Sub
    End Class
End Namespace

COM

// This example shows how to subscribe to multiple events.
//
// 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.

type
  THelperMethods19 = class
    class function ObjectTypeIds_BaseEventType: _UANodeId; static;
    class function UAFilterElements_SimpleAttribute(TypeId: _UANodeId; simpleRelativeBrowsePathString: string): _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_NodeId: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_EventId: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_EventType: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_SourceNode: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_SourceName: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_Time: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_ReceiveTime: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_LocalTime: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_Message: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_Severity: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_AllFields: _UAAttributeFieldCollection; static;
  end;

type
  TClientEventHandlers19 = class
    procedure Client_EventNotification(
      ASender: TObject;
      sender: OleVariant;
      const eventArgs: _EasyUAEventNotificationEventArgs);
  end;

procedure TClientEventHandlers19.Client_EventNotification(
  ASender: TObject;
  sender: OleVariant;
  const eventArgs: _EasyUAEventNotificationEventArgs);
begin
  // Display the event
    WriteLn(eventArgs.ToString);
end;


class procedure SubscribeMultipleMonitoredItems.Events;
var
  Arguments: OleVariant;
  Client: TEasyUAClient;
  ClientEventHandlers: TClientEventHandlers19;
  EndpointDescriptor: string;
  EventFilter1, EventFilter2: _UAEventFilter;
  MonitoredItemArguments1, MonitoredItemArguments2: _EasyUAMonitoredItemArguments;
  MonitoringParameters1, MonitoringParameters2: _UAMonitoringParameters;
  Operand11, Operand21: _UASimpleAttributeOperand;
  Operand12, Operand22: _UALiteralOperand;
  ServerNodeId1, ServerNodeId2: _UANodeId;
  SourceNodeId: _UANodeId;
  WhereClause1, WhereClause2: _UAContentFilterElement;
begin
  EndpointDescriptor := 'opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer';

  // set MonitoredItemArguments1
  // Event filter: The severity is >= 500.
  Operand11 := THelperMethods19.UABaseEventObject_Operands_Severity;
  Operand12 := CoUALiteralOperand.Create;
  Operand12.Value := 500;
  WhereClause1 := CoUAContentFilterElement.Create;
  WhereClause1.FilterOperator := UAFilterOperator_GreaterThanOrEqual;
  WhereClause1.FilterOperands.Add(Operand11);
  WhereClause1.FilterOperands.Add(Operand12);

  EventFilter1 := CoUAEventFilter.Create;
  EventFilter1.SelectClauses := THelperMethods19.UABaseEventObject_AllFields;
  EventFilter1.WhereClause := WhereClause1;

  ServerNodeId1 := CoUANodeId.Create;
  ServerNodeId1.StandardName := 'Server';

  MonitoringParameters1 := CoUAMonitoringParameters.Create;
  MonitoringParameters1.EventFilter := EventFilter1;
  MonitoringParameters1.QueueSize := 1000;
  MonitoringParameters1.SamplingInterval := 1000;

  MonitoredItemArguments1 := CoEasyUAMonitoredItemArguments.Create;
  MonitoredItemArguments1.AttributeId := UAAttributeId_EventNotifier;
  MonitoredItemArguments1.EndpointDescriptor.UrlString := EndpointDescriptor;
  MonitoredItemArguments1.MonitoringParameters := MonitoringParameters1;
  MonitoredItemArguments1.NodeDescriptor.NodeId := ServerNodeId1;
  MonitoredItemArguments1.State := 'firstState';

  // set MonitoredItemArguments2
  // Event filter: The event comes from a specified source node.
  Operand21 := THelperMethods19.UABaseEventObject_Operands_SourceNode;
  SourceNodeId := CoUANodeId.Create;
  SourceNodeId.ExpandedText := 'nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=1:Metals/SouthMotor';
  Operand22 := CoUALiteralOperand.Create;
  Operand22.Value := SourceNodeId;
  WhereClause2 := CoUAContentFilterElement.Create;
  WhereClause2.FilterOperator := UAFilterOperator_Equals;
  WhereClause2.FilterOperands.Add(Operand21);
  WhereClause2.FilterOperands.Add(Operand22);

  EventFilter2 := CoUAEventFilter.Create;
  EventFilter2.SelectClauses := THelperMethods19.UABaseEventObject_AllFields;
  EventFilter2.WhereClause := WhereClause2;

  ServerNodeId2 := CoUANodeId.Create;
  ServerNodeId2.StandardName := 'Server';

  MonitoringParameters2 := CoUAMonitoringParameters.Create;
  MonitoringParameters2.EventFilter := EventFilter2;
  MonitoringParameters2.QueueSize := 1000;
  MonitoringParameters2.SamplingInterval := 2000;

  MonitoredItemArguments2 := CoEasyUAMonitoredItemArguments.Create;
  MonitoredItemArguments2.AttributeId := UAAttributeId_EventNotifier;
  MonitoredItemArguments2.EndpointDescriptor.UrlString := EndpointDescriptor;
  MonitoredItemArguments2.MonitoringParameters := MonitoringParameters2;
  MonitoredItemArguments2.NodeDescriptor.NodeId := ServerNodeId2;
  MonitoredItemArguments2.State := 'secondState';


  // Instantiate the client object and hook events
  Client := TEasyUAClient.Create(nil);
  ClientEventHandlers := TClientEventHandlers19.Create;
  Client.OnEventNotification := ClientEventHandlers.Client_EventNotification;

  Arguments := VarArrayCreate([0, 1], varVariant);
  Arguments[0] := MonitoredItemArguments1;
  Arguments[1] := MonitoredItemArguments2;

  WriteLn('Subscribing...');
  Client.SubscribeMultipleMonitoredItems(Arguments);

  WriteLn('Processing monitored item changed events for 30 seconds...');
  PumpSleep(30*1000);

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

  WriteLn('Waiting for 5 seconds...');
  Sleep(5*1000);

  WriteLn('Finished.');
  VarClear(Arguments);
  FreeAndNil(Client);
  FreeAndNil(ClientEventHandlers);
end;

class function THelperMethods19.ObjectTypeIds_BaseEventType: _UANodeId;
  var NodeId: _UANodeId;
  begin
    NodeId := CoUANodeId.Create;
    NodeId.StandardName := 'BaseEventType';
    Result := NodeId;
  end;

class function THelperMethods19.UAFilterElements_SimpleAttribute(TypeId: _UANodeId; simpleRelativeBrowsePathString: string): _UASimpleAttributeOperand;
var
  BrowsePathParser: _UABrowsePathParser;
  Operand: _UASimpleAttributeOperand;
begin
  BrowsePathParser := CoUABrowsePathParser.Create;
  Operand := CoUASimpleAttributeOperand.Create;
  Operand.TypeId.NodeId := TypeId;
  Operand.QualifiedNames := BrowsePathParser.ParseRelative(simpleRelativeBrowsePathString).ToUAQualifiedNameCollection;
  Result := Operand;
end;

class function THelperMethods19.UABaseEventObject_Operands_NodeId: _UASimpleAttributeOperand;
var
  Operand: _UASimpleAttributeOperand;
begin
  Operand := CoUASimpleAttributeOperand.Create;
  Operand.TypeId.NodeId.StandardName := 'BaseEventType';
  Operand.AttributeId := UAAttributeId_NodeId;
  Result := Operand;
end;

class function THelperMethods19.UABaseEventObject_Operands_EventId: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/EventId');
end;

class function THelperMethods19.UABaseEventObject_Operands_EventType: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/EventType');
end;

class function THelperMethods19.UABaseEventObject_Operands_SourceNode: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/SourceNode');
end;

class function THelperMethods19.UABaseEventObject_Operands_SourceName: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/SourceName');
end;

class function THelperMethods19.UABaseEventObject_Operands_Time: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/Time');
end;

class function THelperMethods19.UABaseEventObject_Operands_ReceiveTime: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/ReceiveTime');
end;

class function THelperMethods19.UABaseEventObject_Operands_LocalTime: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/LocalTime');
end;

class function THelperMethods19.UABaseEventObject_Operands_Message: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/Message');
end;

class function THelperMethods19.UABaseEventObject_Operands_Severity: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/Severity');
end;

class function THelperMethods19.UABaseEventObject_AllFields: _UAAttributeFieldCollection;
var
  Fields: _UAAttributeFieldCollection;
begin
  Fields := CoUAAttributeFieldCollection.Create;
  Fields.Add(UABaseEventObject_Operands_NodeId.ToUAAttributeField);
  Fields.Add(UABaseEventObject_Operands_EventId.ToUAAttributeField);
  Fields.Add(UABaseEventObject_Operands_EventType.ToUAAttributeField);
  Fields.Add(UABaseEventObject_Operands_SourceNode.ToUAAttributeField);
  Fields.Add(UABaseEventObject_Operands_SourceName.ToUAAttributeField);
  Fields.Add(UABaseEventObject_Operands_Time.ToUAAttributeField);
  Fields.Add(UABaseEventObject_Operands_ReceiveTime.ToUAAttributeField);
  Fields.Add(UABaseEventObject_Operands_LocalTime.ToUAAttributeField);
  Fields.Add(UABaseEventObject_Operands_Message.ToUAAttributeField);
  Fields.Add(UABaseEventObject_Operands_Severity.ToUAAttributeField);

  Result := Fields;
end;

// This example shows how to subscribe to multiple events.
//
// 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.

const UAAttributeId_NodeId = 1;
const UAAttributeId_EventNotifier = 12;

const UAFilterOperator_Equals = 1;
const UAFilterOperator_GreaterThanOrEqual = 5;

class ClientEvents {
    function EventNotification($Sender, $E)
    {
        // Display the event
        printf("%s\n", $E);
    }
}

$EndpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

// set MonitoredItemArguments1
// Event filter: The severity is >= 500.
$Operand11 = UABaseEventObject_Operands_Severity();
$Operand12 = new COM("OpcLabs.EasyOpc.UA.Filtering.UALiteralOperand");
$Operand12->Value = 500;
$WhereClause1 = new COM("OpcLabs.EasyOpc.UA.Filtering.UAContentFilterElement");
$WhereClause1->FilterOperator = UAFilterOperator_GreaterThanOrEqual;
$WhereClause1->FilterOperands->Add($Operand11);
$WhereClause1->FilterOperands->Add($Operand12);

$EventFilter1 = new COM("OpcLabs.EasyOpc.UA.UAEventFilter");
$EventFilter1->SelectClauses = UABaseEventObject_AllFields();
$EventFilter1->WhereClause = $WhereClause1;

$ServerNodeId1 = new COM("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId");
$ServerNodeId1->StandardName = "Server";

$MonitoringParameters1 = new COM("OpcLabs.EasyOpc.UA.UAMonitoringParameters");
$MonitoringParameters1->EventFilter = $EventFilter1;
$MonitoringParameters1->QueueSize = 1000;
$MonitoringParameters1->SamplingInterval = 1000;

$MonitoredItemArguments1 = new COM("OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments");
$MonitoredItemArguments1->AttributeId = UAAttributeId_EventNotifier;
$MonitoredItemArguments1->EndpointDescriptor->UrlString = $EndpointDescriptor;
$MonitoredItemArguments1->MonitoringParameters = $MonitoringParameters1;
$MonitoredItemArguments1->NodeDescriptor->NodeId = $ServerNodeId1;
$MonitoredItemArguments1->State = "firstState";

// set MonitoredItemArguments2
// Event filter: The event comes from a specified source node.
$Operand21 = UABaseEventObject_Operands_SourceNode();
$SourceNodeId = new COM("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId");
$SourceNodeId->ExpandedText = "nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=1:Metals/SouthMotor";
$Operand22 = new COM("OpcLabs.EasyOpc.UA.Filtering.UALiteralOperand");
$Operand22->Value = $SourceNodeId;
$WhereClause2 = new COM("OpcLabs.EasyOpc.UA.Filtering.UAContentFilterElement");
$WhereClause2->FilterOperator = UAFilterOperator_Equals;
$WhereClause2->FilterOperands->Add($Operand21);
$WhereClause2->FilterOperands->Add($Operand22);

$EventFilter2 = new COM("OpcLabs.EasyOpc.UA.UAEventFilter");
$EventFilter2->SelectClauses = UABaseEventObject_AllFields();
$EventFilter2->WhereClause = $WhereClause2;

$ServerNodeId2 = new COM("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId");
$ServerNodeId2->StandardName = "Server";

$MonitoringParameters2 = new COM("OpcLabs.EasyOpc.UA.UAMonitoringParameters");
$MonitoringParameters2->EventFilter = $EventFilter2;
$MonitoringParameters2->QueueSize = 1000;
$MonitoringParameters2->SamplingInterval = 2000;

$MonitoredItemArguments2 = new COM("OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments");
$MonitoredItemArguments2->AttributeId = UAAttributeId_EventNotifier;
$MonitoredItemArguments2->EndpointDescriptor->UrlString = $EndpointDescriptor;
$MonitoredItemArguments2->MonitoringParameters = $MonitoringParameters2;
$MonitoredItemArguments2->NodeDescriptor->NodeId = $ServerNodeId2;
$MonitoredItemArguments2->State = "secondState";

// Instantiate the client object and hook events
$Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient");
$ClientEvents = new ClientEvents();
com_event_sink($Client, $ClientEvents, "DEasyUAClientEvents");

$arguments[0] = $MonitoredItemArguments1;
$arguments[1] = $MonitoredItemArguments2;

printf("Subscribing...\n");
$Client->SubscribeMultipleMonitoredItems($arguments);

printf("Processing monitored item changed events for 30 seconds...\n");
$startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 30);

printf("Unsubscribing...\n");
$Client->UnsubscribeAllMonitoredItems;

printf("Waiting for 5 seconds...\n");
$startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 5);


function ObjectTypeIds_BaseEventType() {
    $NodeId = new COM("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId");
    $NodeId->StandardName = "BaseEventType";
    return $NodeId;
}

function UAFilterElements_SimpleAttribute($TypeId, $simpleRelativeBrowsePathString) {
  $BrowsePathParser = new COM("OpcLabs.EasyOpc.UA.Navigation.Parsing.UABrowsePathParser");
  $Operand = new COM("OpcLabs.EasyOpc.UA.Filtering.UASimpleAttributeOperand");
  $Operand->TypeId->NodeId = $TypeId;
  $Operand->QualifiedNames = $BrowsePathParser->ParseRelative($simpleRelativeBrowsePathString)->ToUAQualifiedNameCollection;
  return $Operand;
}

function UABaseEventObject_Operands_NodeId() {
    $Operand = new COM("OpcLabs.EasyOpc.UA.Filtering.UASimpleAttributeOperand");
    $Operand->TypeId->NodeId->StandardName = "BaseEventType";
    $Operand->AttributeId = UAAttributeId_NodeId;
    return $Operand;
}

function UABaseEventObject_Operands_EventId() {
  return UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType(), "/EventId");
}

function UABaseEventObject_Operands_EventType() {
  return UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType(), "/EventType");
}

function UABaseEventObject_Operands_SourceNode() {
  return UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType(), "/SourceNode");
}

function UABaseEventObject_Operands_SourceName() {
  return UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType(), "/SourceName");
}

function UABaseEventObject_Operands_Time() {
  return UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType(), "/Time");
}

function UABaseEventObject_Operands_ReceiveTime() {
  return UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType(), "/ReceiveTime");
}

function UABaseEventObject_Operands_LocalTime() {
  return UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType(), "/LocalTime");
}

function UABaseEventObject_Operands_Message() {
  return UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType(), "/Message");
}

function UABaseEventObject_Operands_Severity() {
  return UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType(), "/Severity");
}


function UABaseEventObject_AllFields() {
    $Fields = new COM("OpcLabs.EasyOpc.UA.UAAttributeFieldCollection");
    $Fields->Add(UABaseEventObject_Operands_NodeId()->ToUAAttributeField);
    $Fields->Add(UABaseEventObject_Operands_EventId()->ToUAAttributeField);
    $Fields->Add(UABaseEventObject_Operands_EventType()->ToUAAttributeField);
    $Fields->Add(UABaseEventObject_Operands_SourceNode()->ToUAAttributeField);
    $Fields->Add(UABaseEventObject_Operands_SourceName()->ToUAAttributeField);
    $Fields->Add(UABaseEventObject_Operands_Time()->ToUAAttributeField);
    $Fields->Add(UABaseEventObject_Operands_ReceiveTime()->ToUAAttributeField);
    $Fields->Add(UABaseEventObject_Operands_LocalTime()->ToUAAttributeField);
    $Fields->Add(UABaseEventObject_Operands_Message()->ToUAAttributeField);
    $Fields->Add(UABaseEventObject_Operands_Severity()->ToUAAttributeField);

    return $Fields;
}

// Example output (truncated):
//Subscribing...
//Processing monitored item changed events for 30 seconds...
//[firstState] Success
//[secondState] Success
//[firstState] Success; Refresh; RefreshInitiated
//[firstState] Success; Refresh; (10 field results) [EastTank] 500! "The alarm was acknoweledged." @10/14/2019 4:00:13 PM
//[firstState] Success; Refresh; (10 field results) [EastTank] 500! "The alarm was acknoweledged." @10/14/2019 4:00:17 PM
//[firstState] Success; Refresh; (10 field results) [NorthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:02 PM
//[firstState] Success; Refresh; (10 field results) [NorthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:16 PM
//[firstState] Success; Refresh; (10 field results) [SouthMotor] 700! "The alarm was acknoweledged." @10/14/2019 4:00:21 PM
//[firstState] Success; Refresh; (10 field results) [SouthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:03 PM
//[firstState] Success; Refresh; RefreshComplete
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:08 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:08 PM
//[secondState] Success; Refresh; RefreshInitiated
//[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The dialog was activated" @9/10/2019 8:08:25 PM
//[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm is active." @11/8/2019 7:48:07 PM
//[secondState] Success; Refresh; (10 field results) [SouthMotor] 700! "The alarm was acknoweledged." @10/14/2019 4:00:21 PM
//[secondState] Success; Refresh; (10 field results) [SouthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:03 PM
//[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm severity has increased." @9/10/2019 8:09:02 PM
//[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm severity has increased." @9/10/2019 8:09:59 PM
//[secondState] Success; Refresh; RefreshComplete
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:09 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:09 PM
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:10 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:10 PM
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:11 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:11 PM
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:12 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:12 PM
//[firstState] Success; (10 field results) [EastTank] 500! "The alarm severity has increased." @11/8/2019 7:48:13 PM
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:13 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:13 PM
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:14 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:14 PM
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:15 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:15 PM
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:16 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:16 PM
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:17 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:17 PM
//[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:18 PM
//[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:18 PM
//[secondState] Success; (10 field results) [SouthMotor] 300! "The alarm severity has increased." @11/8/2019 7:48:18 PM
//...


Rem This example shows how to subscribe to multiple events.
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

Const UAAttributeId_NodeId = 1
Const UAAttributeId_EventNotifier = 12

Const UAFilterOperator_Equals = 1
Const UAFilterOperator_GreaterThanOrEqual = 5

Dim endpointDescriptor
endpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"

' Instantiate the client object and hook events
Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient")
WScript.ConnectObject Client, "Client_"

Dim arguments(1)
Set arguments(0) = CreateMonitoredItemArguments1
Set arguments(1) = CreateMonitoredItemArguments2

WScript.Echo "Subscribing..."
Client.SubscribeMultipleMonitoredItems arguments

WScript.Echo "Processing monitored item changed events for 30 seconds..."
WScript.Sleep 30 * 1000

WScript.Echo "Unsubscribing..."
Client.UnsubscribeAllMonitoredItems

WScript.Echo "Waiting for 5 seconds..."
WScript.Sleep 5 * 1000



Function ObjectTypeIds_BaseEventType
    Dim NodeId: Set NodeId = CreateObject("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId")
    NodeId.StandardName = "BaseEventType"
    Set ObjectTypeIds_BaseEventType = NodeId
End Function

Function UAFilterElements_SimpleAttribute(TypeId, simpleRelativeBrowsePathString)
    Dim BrowsePathParser: Set BrowsePathParser = CreateObject("OpcLabs.EasyOpc.UA.Navigation.Parsing.UABrowsePathParser")
    Dim Operand: Set Operand = CreateObject("OpcLabs.EasyOpc.UA.Filtering.UASimpleAttributeOperand")
    Set Operand.TypeId.NodeId = TypeId
    Set Operand.QualifiedNames = BrowsePathParser.ParseRelative(simpleRelativeBrowsePathString).ToUAQualifiedNameCollection
    Set UAFilterElements_SimpleAttribute = Operand
End Function

Function UABaseEventObject_Operands_NodeId
    Dim Operand: Set Operand = CreateObject("OpcLabs.EasyOpc.UA.Filtering.UASimpleAttributeOperand")
    Operand.TypeId.NodeId.StandardName = "BaseEventType"
    Operand.AttributeId = UAAttributeId_NodeId
    Set UABaseEventObject_Operands_NodeId = Operand
End Function

Function UABaseEventObject_Operands_EventId
    Set UABaseEventObject_Operands_EventId = UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, "/EventId")
End Function

Function UABaseEventObject_Operands_EventType
    Set UABaseEventObject_Operands_EventType = UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, "/EventType")
End Function

Function UABaseEventObject_Operands_SourceNode
    Set UABaseEventObject_Operands_SourceNode = UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, "/SourceNode")
End Function

Function UABaseEventObject_Operands_SourceName
    Set UABaseEventObject_Operands_SourceName = UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, "/SourceName")
End Function

Function UABaseEventObject_Operands_Time
    Set UABaseEventObject_Operands_Time = UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, "/Time")
End Function

Function UABaseEventObject_Operands_ReceiveTime
    Set UABaseEventObject_Operands_ReceiveTime = UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, "/ReceiveTime")
End Function

Function UABaseEventObject_Operands_LocalTime
    Set UABaseEventObject_Operands_LocalTime = UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, "/LocalTime")
End Function

Function UABaseEventObject_Operands_Message
    Set UABaseEventObject_Operands_Message = UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, "/Message")
End Function

Function UABaseEventObject_Operands_Severity
    Set UABaseEventObject_Operands_Severity = UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, "/Severity")
End Function

Function UABaseEventObject_AllFields
    Dim Fields: Set Fields = CreateObject("OpcLabs.EasyOpc.UA.UAAttributeFieldCollection")

    Fields.Add UABaseEventObject_Operands_NodeId.ToUAAttributeField

    Fields.Add UABaseEventObject_Operands_EventId.ToUAAttributeField
    Fields.Add UABaseEventObject_Operands_EventType.ToUAAttributeField
    Fields.Add UABaseEventObject_Operands_SourceNode.ToUAAttributeField
    Fields.Add UABaseEventObject_Operands_SourceName.ToUAAttributeField
    Fields.Add UABaseEventObject_Operands_Time.ToUAAttributeField
    Fields.Add UABaseEventObject_Operands_ReceiveTime.ToUAAttributeField
    Fields.Add UABaseEventObject_Operands_LocalTime.ToUAAttributeField
    Fields.Add UABaseEventObject_Operands_Message.ToUAAttributeField
    Fields.Add UABaseEventObject_Operands_Severity.ToUAAttributeField

    Set UABaseEventObject_AllFields = Fields
End Function

Function CreateMonitoredItemArguments1
    ' Event filter: The severity is >= 500.
    Dim Operand1: Set Operand1 = UABaseEventObject_Operands_Severity
    Dim Operand2: Set Operand2 = CreateObject("OpcLabs.EasyOpc.UA.Filtering.UALiteralOperand")
    Operand2.Value = 500
    Dim WhereClause: Set WhereClause = CreateObject("OpcLabs.EasyOpc.UA.Filtering.UAContentFilterElement")
    WhereClause.FilterOperator = UAFilterOperator_GreaterThanOrEqual
    WhereClause.FilterOperands.Add Operand1
    WhereClause.FilterOperands.Add Operand2

    Dim EventFilter: Set EventFilter = CreateObject("OpcLabs.EasyOpc.UA.UAEventFilter")
    Set EventFilter.SelectClauses = UABaseEventObject_AllFields
    Set EventFilter.WhereClause = WhereClause

    Dim ServerNodeId: Set ServerNodeId = CreateObject("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId")
    ServerNodeId.StandardName = "Server"

    Dim MonitoringParameters: Set MonitoringParameters = CreateObject("OpcLabs.EasyOpc.UA.UAMonitoringParameters")
    Set MonitoringParameters.EventFilter = EventFilter
    MonitoringParameters.QueueSize = 1000
    MonitoringParameters.SamplingInterval = 1000

    Dim MonitoredItemArguments: Set MonitoredItemArguments = CreateObject("OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments")
    MonitoredItemArguments.AttributeId = UAAttributeId_EventNotifier
    MonitoredItemArguments.EndpointDescriptor.UrlString = endpointDescriptor
    Set MonitoredItemArguments.MonitoringParameters = MonitoringParameters
    Set MonitoredItemArguments.NodeDescriptor.NodeId = ServerNodeId
    MonitoredItemArguments.State = "firstState"

    Set CreateMonitoredItemArguments1 = MonitoredItemArguments
End Function

Function CreateMonitoredItemArguments2
    ' Event filter: The event comes from a specified source node.
    Dim Operand1: Set Operand1 = UABaseEventObject_Operands_SourceNode
    Dim SourceNodeId: Set SourceNodeId = CreateObject("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId")
    SourceNodeId.ExpandedText = "nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=1:Metals/SouthMotor"
    Dim Operand2: Set Operand2 = CreateObject("OpcLabs.EasyOpc.UA.Filtering.UALiteralOperand")
    Set Operand2.Value = SourceNodeId
    Dim WhereClause: Set WhereClause = CreateObject("OpcLabs.EasyOpc.UA.Filtering.UAContentFilterElement")
    WhereClause.FilterOperator = UAFilterOperator_Equals
    WhereClause.FilterOperands.Add Operand1
    WhereClause.FilterOperands.Add Operand2

    Dim EventFilter: Set EventFilter = CreateObject("OpcLabs.EasyOpc.UA.UAEventFilter")
    Set EventFilter.SelectClauses = UABaseEventObject_AllFields
    Set EventFilter.WhereClause = WhereClause

    Dim ServerNodeId: Set ServerNodeId = CreateObject("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId")
    ServerNodeId.StandardName = "Server"

    Dim MonitoringParameters: Set MonitoringParameters = CreateObject("OpcLabs.EasyOpc.UA.UAMonitoringParameters")
    Set MonitoringParameters.EventFilter = EventFilter
    MonitoringParameters.QueueSize = 1000
    MonitoringParameters.SamplingInterval = 2000

    Dim MonitoredItemArguments: Set MonitoredItemArguments = CreateObject("OpcLabs.EasyOpc.UA.OperationModel.EasyUAMonitoredItemArguments")
    MonitoredItemArguments.AttributeId = UAAttributeId_EventNotifier
    MonitoredItemArguments.EndpointDescriptor.UrlString = endpointDescriptor
    Set MonitoredItemArguments.MonitoringParameters = MonitoringParameters
    Set MonitoredItemArguments.NodeDescriptor.NodeId = ServerNodeId
    MonitoredItemArguments.State = "secondState"

    Set CreateMonitoredItemArguments2 = MonitoredItemArguments
End Function

Sub Client_EventNotification(Sender, e)
    ' Display the event
    WScript.Echo e
End Sub



' Example output (truncated):
'Subscribing...
'Processing monitored item changed events for 30 seconds...
'[firstState] Success
'[secondState] Success
'[firstState] Success; Refresh; RefreshInitiated
'[firstState] Success; Refresh; (10 field results) [EastTank] 500! "The alarm was acknoweledged." @10/14/2019 4:00:13 PM
'[firstState] Success; Refresh; (10 field results) [EastTank] 500! "The alarm was acknoweledged." @10/14/2019 4:00:17 PM
'[firstState] Success; Refresh; (10 field results) [NorthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:02 PM
'[firstState] Success; Refresh; (10 field results) [NorthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:16 PM
'[firstState] Success; Refresh; (10 field results) [SouthMotor] 700! "The alarm was acknoweledged." @10/14/2019 4:00:21 PM
'[firstState] Success; Refresh; (10 field results) [SouthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:03 PM
'[firstState] Success; Refresh; RefreshComplete
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:08 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:08 PM
'[secondState] Success; Refresh; RefreshInitiated
'[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The dialog was activated" @9/10/2019 8:08:25 PM
'[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm is active." @11/8/2019 7:48:07 PM
'[secondState] Success; Refresh; (10 field results) [SouthMotor] 700! "The alarm was acknoweledged." @10/14/2019 4:00:21 PM
'[secondState] Success; Refresh; (10 field results) [SouthMotor] 500! "The alarm was acknoweledged." @10/14/2019 4:00:03 PM
'[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm severity has increased." @9/10/2019 8:09:02 PM
'[secondState] Success; Refresh; (10 field results) [SouthMotor] 100! "The alarm severity has increased." @9/10/2019 8:09:59 PM
'[secondState] Success; Refresh; RefreshComplete
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:09 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:09 PM
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:10 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:10 PM
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:11 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:11 PM
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:12 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:12 PM
'[firstState] Success; (10 field results) [EastTank] 500! "The alarm severity has increased." @11/8/2019 7:48:13 PM
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:13 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:13 PM
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:14 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:14 PM
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:15 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:15 PM
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:16 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:16 PM
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:17 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:17 PM
'[firstState] Success; (10 field results) [Internal] 500! "Raising Events" @11/8/2019 7:48:18 PM
'[firstState] Success; (10 field results) [Internal] 500! "Events Raised" @11/8/2019 7:48:18 PM
'[secondState] Success; (10 field results) [SouthMotor] 300! "The alarm severity has increased." @11/8/2019 7:48:18 PM
'...

Python

# This example shows how to subscribe to multiple events.
#
# 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 .
# 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.
# 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.AddressSpace import *
from OpcLabs.EasyOpc.UA.AddressSpace.Standard import *
from OpcLabs.EasyOpc.UA.AlarmsAndConditions import *
from OpcLabs.EasyOpc.UA.Filtering import *
from OpcLabs.EasyOpc.UA.OperationModel import *


def eventNotification(sender, eventArgs):
    # Display the event.
    print(eventArgs)


# Define which server we will work with.
endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer')

# Instantiate the client object and hook events.
client = EasyUAClient()
client.EventNotification += eventNotification

print('Subscribing...')

eventFilterBuilder1 = UAEventFilterBuilder(
    UAFilterElements.GreaterThanOrEqual(UABaseEventObject.Operands.Severity, 500),
    UABaseEventObject.AllFields)
monitoringItemArguments1 = EasyUAMonitoredItemArguments('firstState',
    endpointDescriptor,
    UANodeDescriptor(UAObjectIds.Server),
    UAMonitoringParameters(1000, UAEventFilterBuilder.ToUAEventFilter(eventFilterBuilder1)))
monitoringItemArguments1.AttributeId = UAAttributeId.EventNotifier

eventFilterBuilder2 = UAEventFilterBuilder(
    UAFilterElements.Equals(
        UABaseEventObject.Operands.SourceNode,
        UANodeId('nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=1:Metals/SouthMotor')),
    UABaseEventObject.AllFields)
monitoringItemArguments2 = EasyUAMonitoredItemArguments('secondState',
    endpointDescriptor,
    UANodeDescriptor(UAObjectIds.Server),
    UAMonitoringParameters(2000, UAEventFilterBuilder.ToUAEventFilter(eventFilterBuilder2)))
monitoringItemArguments2.AttributeId = UAAttributeId.EventNotifier

IEasyUAClientExtension.SubscribeMultipleMonitoredItems(client, [monitoringItemArguments1, monitoringItemArguments2])

print('Processing event notifications for 30 seconds...')
time.sleep(30)

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

print('Waiting for 5 seconds...')
time.sleep(5)

print('Finished.')

 

Differences between various OPC UA subscription methods

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.

More examples

The example below logs OPC Alarms and Events notifications into an XML file.

The main program:

// Logs OPC UA Alarms&Conditions event notifications into an XML file.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// 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.

using System;
using System.Diagnostics;
using System.Xml;
using System.Xml.Serialization;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.AddressSpace.Standard;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UAXmlEventLogger
{
    class Program
    {
        static void Main()
        {
            // Define which server we will work with.
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

            Console.WriteLine("Starting up...");
            var xmlSerializer = new XmlSerializer(typeof(EasyUAEventNotificationEventArgs));
            var xmlWriter = XmlWriter.Create("UAEvents.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("ArrayOfEasyUAEventNotificationEventArgs");

            Console.WriteLine("Logging events for 30 seconds...");
            int handle = EasyUAClient.SharedInstance.SubscribeEvent(endpointDescriptor, UAObjectIds.Server, 
                samplingInterval:1000,
                (_, 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.");
        }
    }
}

 

 

See Also
Specifying Event Filters (OPC UA Alarms & Conditions)
Changing Existing Subscription (OPC UA Alarms & Conditions)
Unsubscribing from OPC UA Events
Refreshing Condition States (OPC UA Alarms & Conditions)
OPC UA A&C Notification Event
Using Callback Methods Instead of Event Handler (OPC UA Alarms & Conditions)
Subscribing to Information (OPC UA Alarms & Conditions)
Imperative Programming Model for OPC UA Alarms & Conditions
Imperative Programming Model
Subscribing to OPC UA Data Changes

Installed Examples - Client Console

Installed Examples - Client Console - UAXmlEventLogger

 

 

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