Browsing for OPC UA Event Sources

In order to browse for event sources, you can use the pre-made browse parameters available in the UABrowseParameters.EventSources static property, and call the IEasyUAClient.Browse Method with them. Alternatively, you can use a dedicated extension method, IEasyUAClient.BrowseEventSources, to perform browsing for event sources easily.

.NET

// This example shows how to browse objects under the "Objects" node and display event sources.

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

namespace UADocExamples.AlarmsAndConditions
{
    class BrowseEventSources
    {
        public static void Overload2()
        {
            // Start browsing from the "Objects" node.
            try
            {
                BrowseFrom(UAObjectIds.ObjectsFolder);
            }
            catch (UAException uaException)
            {
                Console.WriteLine($"*** Failure: {uaException.GetBaseException().Message}");
            }

            Console.WriteLine();
            Console.WriteLine("Finished.");
        }

        private static void BrowseFrom(UANodeDescriptor nodeDescriptor)
        {
            // Define which server we will work with.
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

            Console.WriteLine();
            Console.WriteLine();
            Console.WriteLine($"Parent node: {nodeDescriptor}");

            // Instantiate the client object.
            var client = new EasyUAClient();

            // Obtain event sources.
            UANodeElementCollection eventSourceNodeElementCollection = client.BrowseEventSources(
                endpointDescriptor, nodeDescriptor);

            // Display event sources.
            if (eventSourceNodeElementCollection.Count != 0)
            {
                Console.WriteLine();
                Console.WriteLine("Event sources:");
                foreach (UANodeElement eventSourceNodeElement in eventSourceNodeElementCollection)
                    Console.WriteLine(eventSourceNodeElement);
            }

            // Obtain objects.
            UANodeElementCollection objectNodeElementCollection = client.BrowseObjects(
                endpointDescriptor, nodeDescriptor);

            // Recurse.
            foreach (UANodeElement objectNodeElement in objectNodeElementCollection)
                BrowseFrom(objectNodeElement);
        }


        // Example output (truncated):
        //
        //
        //Parent node: ObjectsFolder
        //
        //
        //Parent node: Server
        //
        //Event sources:
        //Green -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Green (Object)
        //Yellow -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Yellow (Object)
        //
        //
        //Parent node: Server_ServerCapabilities
        //...
    }
}

# This example shows how to browse objects under the "Objects" node and display event sources.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.UA
using namespace OpcLabs.EasyOpc.UA.AddressSpace.Standard
using namespace OpcLabs.EasyOpc.UA.Navigation.Parsing;
using namespace OpcLabs.EasyOpc.UA.OperationModel


function BrowseEventSourcesFrom([UANodeDescriptor]$nodeDescriptor) { 

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

    Write-Host
    Write-Host
    Write-Host "Parent node: $($nodeDescriptor)"

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

    # Obtain event sources.
    $eventSourceNodeElementCollection = [IEasyUAClientExtension]::BrowseEventSources($client,
        $endpointDescriptor, $nodeDescriptor)

    # Display event sources.
    if ($eventSourceNodeElementCollection.Count -ne 0) {
        Write-Host
        Write-Host "Event sources:"
        foreach ($eventSourceNodeElement in $eventSourceNodeElementCollection) {
            Write-Host $eventSourceNodeElement
        }
    }

    # Obtain objects.
    $objectNodeElementCollection = [IEasyUAClientExtension]::BrowseObjects($client,
        $endpointDescriptor, $nodeDescriptor)

    # Recurse.
    foreach ($objectNodeElement in $objectNodeElementCollection) {
        BrowseEventSourcesFrom($objectNodeElement)
    }
}


# 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"

# Start browsing from the "Objects" node.
try {
    [UANodeDescriptor]$startingNodeDescriptor = [UAObjectIds]::ObjectsFolder
    BrowseEventSourcesFrom $startingNodeDescriptor
}
catch [UAException] {
    Write-Host "*** Failure: $($PSItem.Exception.GetBaseException().Message)"
    return
}

Write-Host
Write-Host "Finished."


# Example output (truncated):
#
#
#Parent node: ObjectsFolder
#
#
#Parent node: Server
#
#Event sources:
#Green -> nsu=http:#opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Green (Object)
#Yellow -> nsu=http:#opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Yellow (Object)
#
#
#Parent node: Server_ServerCapabilities
#...

# This example shows how to browse objects under the "Objects" node and display event sources.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# 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.OperationModel import *


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


def browseFrom(nodeDescriptor):
    global endpointDescriptor

    print()
    print()
    print('Parent node: ', nodeDescriptor, sep='')

    # Instantiate the client object.
    client = EasyUAClient()

    # Obtain event sources.
    eventSourceNodeElementCollection = IEasyUAClientExtension.BrowseEventSources(client,
                                                                                 endpointDescriptor,
                                                                                 nodeDescriptor)

    # Display event sources.
    if eventSourceNodeElementCollection.Count != 0:
        print('')
        print('Event sources:')
        for eventSourceNodeElement in eventSourceNodeElementCollection:
            print(eventSourceNodeElement)

    # Obtain objects.
    objectNodeElementCollection = IEasyUAClientExtension.BrowseObjects(client,
                                                                       endpointDescriptor,
                                                                       nodeDescriptor)

    # Recurse.
    for objectNodeElement in objectNodeElementCollection:
        browseFrom(objectNodeElement.ToUANodeDescriptor())


# Start browsing from the "Objects" node.
try:
    browseFrom(UANodeDescriptor(UAObjectIds.ObjectsFolder))
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

print()
print('Finished.')

' This example shows how to browse objects under the "Objects" node and display event sources.

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

Namespace AlarmsAndConditions
    Friend Class BrowseEventSources
        Public Shared Sub Overload2()

            ' Start browsing from the "Objects" node
            Try
                BrowseFrom(UAObjectIds.ObjectsFolder)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
            End Try
        End Sub

        Private Shared Sub BrowseFrom(nodeDescriptor As UANodeDescriptor)

            Console.WriteLine()
            Console.WriteLine()
            Console.WriteLine("Parent node: {0}", nodeDescriptor)

            ' Instantiate the client object
            Dim client = New EasyUAClient()

            ' Obtain notifiers
            Dim eventSourceNodeElementCollection As UANodeElementCollection = client.BrowseEventSources( _
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer", _
                nodeDescriptor)

            ' Display notifiers
            Console.WriteLine()
            Console.WriteLine("Event sources:")
            For Each eventSourceNodeElement As UANodeElement In eventSourceNodeElementCollection
                Console.WriteLine(eventSourceNodeElement)
            Next eventSourceNodeElement

            ' Obtain objects
            Dim objectNodeElementCollection = client.BrowseObjects( _
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer", _
                nodeDescriptor)

            ' Recurse
            For Each objectNodeElement As UANodeElement In objectNodeElementCollection
                BrowseFrom(objectNodeElement)
            Next objectNodeElement
        End Sub
    End Class
End Namespace

COM

// This example shows how to browse objects under the "Objects" node and display event sources.

class procedure BrowseEventSources.Main;
var
  ObjectNodeId: _UANodeId;
begin
  ObjectNodeId := CoUANodeId.Create;
  ObjectNodeId.StandardName := 'Objects';
  try
    BrowseFrom(ObjectNodeId);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;
end;

class procedure BrowseEventSources.BrowseFrom(NodeId: _UANodeId);
var
  Client: OpcLabs_EasyOpcUA_TLB._EasyUAClient;
  Count: Cardinal;
  Element: OleVariant;
  EndpointDescriptor: string;
  EventSourceNodeElement: _UANodeElement;
  EventSourceNodeElementEnumerator: IEnumVariant;
  EventSourceNodeElements: _UANodeElementCollection;
  ObjectNodeElement: _UANodeElement;
  ObjectNodeElementEnumerator: IEnumVariant;
  ObjectNodeElements: _UANodeElementCollection;
begin
  EndpointDescriptor := 'opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer';

  WriteLn;
  WriteLn;
  WriteLn('Parent node: ', NodeId.ToString);

  // Instantiate the client object
  Client := CoEasyUAClient.Create;

  // Obtain event sources
  EventSourceNodeElements := Client.BrowseEventSources(EndpointDescriptor, NodeId.ExpandedText);

  // Display event sources
  if EventSourceNodeElements.Count <> 0 then
  begin
    WriteLn;
    WriteLn('Event sources:');
    EventSourceNodeElementEnumerator := EventSourceNodeElements.GetEnumerator;
    while (EventSourceNodeElementEnumerator.Next(1, Element, Count) = S_OK) do
    begin
      EventSourceNodeElement := IUnknown(Element) as _UANodeElement;
      WriteLn(EventSourceNodeElement.ToString);
    end;
  end;

  // Obtain objects
  ObjectNodeElements := Client.BrowseObjects(EndpointDescriptor, NodeId.ExpandedText);

  // Recurse
  ObjectNodeElementEnumerator := ObjectNodeElements.GetEnumerator;
  while (ObjectNodeElementEnumerator.Next(1, Element, Count) = S_OK) do
  begin
    ObjectNodeElement := IUnknown(Element) as _UANodeElement;
    BrowseFrom(ObjectNodeElement.NodeId);
  end;
end;

// This example shows how to browse objects under the "Objects" node and display event sources.


// Start browsing from the "Objects" node
$ObjectNodeId = new COM("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId");
$ObjectNodeId->StandardName = "Objects";
try
{
    BrowseFrom($ObjectNodeId);
}
catch (com_exception $e)
{
    printf("*** Failure: %s\n", $e->getMessage());
    exit();
}

function BrowseFrom($NodeId) {
    $EndpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

    printf("\n");
    printf("\n");
    printf("Parent node: %s\n", $NodeId);

    // Instantiate the client object
    $Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient");

    // Obtain event sources
    $EventSourceNodeElements = $Client->BrowseEventSources($EndpointDescriptor, $NodeId->ExpandedText);

    // Display event sources
    if ($EventSourceNodeElements->Count != 0) {
        printf("\n");
        printf("Event sources:\n");
        foreach ($EventSourceNodeElements as $EventSourceNodeElement)
        {
             printf("%s\n", $EventSourceNodeElement);
        }
     }

    // Obtain objects
    $ObjectNodeElements = $Client->BrowseObjects($EndpointDescriptor, $NodeId->ExpandedText);

    // Recurse
    foreach ($ObjectNodeElements as $ObjectNodeElement)
    {
         BrowseFrom($ObjectNodeElement->NodeId);
    }
}

// Example output (truncated):
//
//
//Parent node: ObjectsFolder
//
//
//Parent node: Server
//
//Event sources:
//Green -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Green (Object)
//Yellow -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Yellow (Object)
//
//
//Parent node: Server_ServerCapabilities
//...

Rem This example shows how to browse objects under the "Objects" node and display event sources.

Option Explicit

' Start browsing from the "Objects" node
Dim ObjectsNodeId: Set ObjectsNodeId = CreateObject("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId")
ObjectsNodeId.StandardName = "Objects"
On Error Resume Next
BrowseFrom ObjectsNodeId
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0



Sub BrowseFrom(NodeId)
    Dim endpointDescriptor
    endpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"

    WScript.Echo 
    WScript.Echo 
    WScript.Echo "Parent node: " & NodeId

    ' Instantiate the client object
    Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient")

    ' Obtain event sources
    Dim EventSourceNodeElementCollection: Set EventSourceNodeElementCollection = Client.BrowseEventSources( _
        endpointDescriptor, NodeId.ExpandedText)

    ' Display event sources
    If EventSourceNodeElementCollection.Count <> 0 Then
        WScript.Echo 
        WScript.Echo "Event sources:"
        Dim EventSourceNodeElement: For Each EventSourceNodeElement In EventSourceNodeElementCollection
            WScript.Echo EventSourceNodeElement
        Next
    End If
    
    ' Obtain objects
    Dim ObjectNodeElementCollection: Set ObjectNodeElementCollection = Client.BrowseObjects( _
        endpointDescriptor, NodeId.ExpandedText)

    ' Recurse
    Dim ObjectNodeElement: For Each ObjectNodeElement In ObjectNodeElementCollection
        BrowseFrom ObjectNodeElement.NodeId
    Next
End Sub



' Example output (truncated):
'
'
'Parent node: ObjectsFolder
'
'
'Parent node: Server
'
'Event sources:
'Green -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Green (Object)
'Yellow -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Yellow (Object)
'
'
'Parent node: Server_ServerCapabilities
'...

Examples - OPC UA Alarms&Conditions

Examples - OPC UA Alarms&Conditions - Browsing for event sources