Connectivity Software User's Guide and Reference
SubscribeEdgeNodeMetric(IEasySparkplugConsumer,SparkplugHostDescriptor,String,String,String) Method
Example 



OpcLabs.EasySparkplug Assembly > OpcLabs.EasySparkplug Namespace > IEasySparkplugConsumerExtension Class > SubscribeEdgeNodeMetric Method : SubscribeEdgeNodeMetric(IEasySparkplugConsumer,SparkplugHostDescriptor,String,String,String) Method
The consumer object that will perform the operation.

The value of this parameter cannot be null (Nothing in Visual Basic).

The Sparkplug host descriptor.

The value of this parameter cannot be null (Nothing in Visual Basic).

The Sparkplug group ID.

The value represents a Sparkplug group ID, or a filter for Sparkplug group IDs. It must be a string with valid UTF-8 characters except for the reserved character '/' (forward slash). Characters '+' (plus) and '#' are filters, and can only be used when they are the single character in the string.

The value of this parameter cannot be null (Nothing in Visual Basic).

The Sparkplug edge node ID.

The value represents a Sparkplug edge node ID, or a filter for Sparkplug edge node IDs. It must be a string with valid UTF-8 characters except for the reserved character '/' (forward slash). Characters '+' (plus) and '#' are filters, and can only be used when they are the single character in the string.

The value of this parameter cannot be null (Nothing in Visual Basic).

The Sparkplug metric name.

The value of this parameter cannot be null (Nothing in Visual Basic).

Subscribes to an edge node metric, specifying the host descriptor, group ID, edge node ID and metric name.
Syntax
'Declaration
 
<ExtensionAttribute()>
Public Overloads Shared Function SubscribeEdgeNodeMetric( _
   ByVal consumer As IEasySparkplugConsumer, _
   ByVal hostDescriptor As SparkplugHostDescriptor, _
   ByVal groupId As String, _
   ByVal edgeNodeId As String, _
   ByVal metricName As String _
) As Integer
'Usage
 
Dim consumer As IEasySparkplugConsumer
Dim hostDescriptor As SparkplugHostDescriptor
Dim groupId As String
Dim edgeNodeId As String
Dim metricName As String
Dim value As Integer
 
value = IEasySparkplugConsumerExtension.SubscribeEdgeNodeMetric(consumer, hostDescriptor, groupId, edgeNodeId, metricName)

Parameters

consumer
The consumer object that will perform the operation.

The value of this parameter cannot be null (Nothing in Visual Basic).

hostDescriptor
The Sparkplug host descriptor.

The value of this parameter cannot be null (Nothing in Visual Basic).

groupId
The Sparkplug group ID.

The value represents a Sparkplug group ID, or a filter for Sparkplug group IDs. It must be a string with valid UTF-8 characters except for the reserved character '/' (forward slash). Characters '+' (plus) and '#' are filters, and can only be used when they are the single character in the string.

The value of this parameter cannot be null (Nothing in Visual Basic).

edgeNodeId
The Sparkplug edge node ID.

The value represents a Sparkplug edge node ID, or a filter for Sparkplug edge node IDs. It must be a string with valid UTF-8 characters except for the reserved character '/' (forward slash). Characters '+' (plus) and '#' are filters, and can only be used when they are the single character in the string.

The value of this parameter cannot be null (Nothing in Visual Basic).

metricName
The Sparkplug metric name.

The value of this parameter cannot be null (Nothing in Visual Basic).

Return Value

Returns a metric subscription handle that can be used to unsubscribe.
Exceptions
ExceptionDescription

A null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.

This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

Remarks

To unsubscribe from the metric, use the UnsubscribeMetric, UnsubscribeAllMetrics or UnsubscribeAll method.

This is an extension method (info: C#, VB.NET). In languages that have support for extensions methods (such as C# and VB.NET), you can use the extension method as if it were a regular method on the object that is its first parameter. In other languages (such as with Python.NET), you will call the extension as a static method, and pass it the object on which it acts as its first parameter.

 

Sparkplug is a trademark of Eclipse Foundation, Inc. "MQTT" is a trademark of the OASIS Open standards consortium. Other related terms are trademarks of their respective owners. Any use of these terms on this site is for descriptive purposes only and does not imply any sponsorship, endorsement or affiliation.

Example
// This example shows how to subscribe to all metrics of a given edge node and display the name and value of the metric with
// each notification.
//
// In order to publish or observe messages for this example, start the SparkplugEdgeNodeConsoleDemo program first.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-ConnectivityStudio/Latest/examples.html .
// Sparkplug examples in C# on GitHub: https://github.com/OPCLabs/Examples-ConnectivityStudio-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.EasySparkplug;
using OpcLabs.EasySparkplug.OperationModel;

namespace SparkplugDocExamples.Consumer._EasySparkplugConsumer
{
    partial class SubscribeEdgeNodeMetric
    {
        public static void Overload1()
        {
            // Note that the default port for the "mqtt" scheme is 1883.
            var hostDescriptor = new SparkplugHostDescriptor("mqtt://localhost");

            // Instantiate the consumer object and hook events.
            var consumer = new EasySparkplugConsumer();
            consumer.MetricNotification += consumer_Overload1_MetricNotification;

            Console.WriteLine("Subscribing...");
            // In this example, we specify the precise Sparkplug group ID and edge node ID, but allow any metric name.
            consumer.SubscribeEdgeNodeMetric(hostDescriptor, 
                "easyGroup", "easySparkplugDemo", "#");

            Console.WriteLine("Processing notifications for 20 seconds...");
            System.Threading.Thread.Sleep(20 * 1000);

            Console.WriteLine("Unsubscribing...");
            consumer.UnsubscribeAllMetrics();

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

            Console.WriteLine("Finished.");
        }


        static void consumer_Overload1_MetricNotification(object sender, EasySparkplugMetricNotificationEventArgs eventArgs)
        {
            // Handle different types of notifications.
            Console.WriteLine();
            switch (eventArgs.NotificationType)
            {
                case SparkplugNotificationType.Connect:
                    Console.WriteLine($"Connected to Sparkplug host, client ID: {eventArgs.ClientId}.");
                    break;
                case SparkplugNotificationType.Disconnect:
                    Console.WriteLine("Disconnected from Sparkplug host.");
                    break;
                case SparkplugNotificationType.Data:
                    Console.WriteLine("Received data from Sparkplug host.");
                    Console.WriteLine($"Metric name: {eventArgs.MetricName}");
                    Console.WriteLine($"Value: {eventArgs.MetricData?.Value}");
                    break;
                case SparkplugNotificationType.Birth:
                    Console.WriteLine("Received birth message from Sparkplug host.");
                    Console.WriteLine($"Metric name: {eventArgs.MetricName}");
                    Console.WriteLine($"Value: {eventArgs.MetricData?.Value}");
                    break;
                case SparkplugNotificationType.Death:
                    Console.WriteLine("Received death message from Sparkplug host.");
                    Console.WriteLine($"Metric name: {eventArgs.MetricName}");
                    break;
            }
            if (!eventArgs.Succeeded)
                Console.WriteLine($"*** Failure: {eventArgs.ErrorMessageBrief}");
        }
    }
}
' This example shows how to subscribe to all metrics of a given edge node and display the name and value of the metric with
' each notification.
'
' In order to publish or observe messages for this example, start the SparkplugEdgeNodeConsoleDemo program first.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-ConnectivityStudio/Latest/examples.html .
' Sparkplug examples in C# on GitHub: https://github.com/OPCLabs/Examples-ConnectivityStudio-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.

Imports OpcLabs.EasySparkplug
Imports OpcLabs.EasySparkplug.OperationModel

Namespace Global.SparkplugDocExamples.Consumer._EasySparkplugConsumer
    Partial Class SubscribeEdgeNodeMetric
        Public Shared Sub Overload1()
            ' Note that the default port for the "mqtt" scheme is 1883.
            Dim hostDescriptor = New SparkplugHostDescriptor("mqtt://localhost")

            ' Instantiate the consumer object and hook events.
            Dim consumer = New EasySparkplugConsumer()
            AddHandler consumer.MetricNotification, AddressOf consumer_Overload1_MetricNotification

            Console.WriteLine("Subscribing...")
            ' In this example, we specify the precise Sparkplug group ID and edge node ID, but allow any metric name.
            consumer.SubscribeEdgeNodeMetric(hostDescriptor,
                "easyGroup", "easySparkplugDemo", "#")

            Console.WriteLine("Processing notifications for 20 seconds...")
            Threading.Thread.Sleep(20 * 1000)

            Console.WriteLine("Unsubscribing...")
            consumer.UnsubscribeAllMetrics()

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

            Console.WriteLine("Finished.")
        End Sub

        Private Shared Sub consumer_Overload1_MetricNotification(ByVal sender As Object, ByVal eventArgs As EasySparkplugMetricNotificationEventArgs)
            ' Handle different types of notifications.
            Console.WriteLine()
            Select Case eventArgs.NotificationType
                Case SparkplugNotificationType.Connect
                    Console.WriteLine($"Connected to Sparkplug host, client ID: {eventArgs.ClientId}.")
                Case SparkplugNotificationType.Disconnect
                    Console.WriteLine("Disconnected from Sparkplug host.")
                Case SparkplugNotificationType.Data
                    Console.WriteLine("Received data from Sparkplug host.")
                    Console.WriteLine($"Metric name: {eventArgs.MetricName}")
                    Console.WriteLine($"Value: {eventArgs.MetricData?.Value}")
                Case SparkplugNotificationType.Birth
                    Console.WriteLine("Received birth message from Sparkplug host.")
                    Console.WriteLine($"Metric name: {eventArgs.MetricName}")
                    Console.WriteLine($"Value: {eventArgs.MetricData?.Value}")
                Case SparkplugNotificationType.Death
                    Console.WriteLine("Received death message from Sparkplug host.")
                    Console.WriteLine($"Metric name: {eventArgs.MetricName}")
            End Select
            If Not eventArgs.Succeeded Then
                Console.WriteLine($"*** Failure: {eventArgs.ErrorMessageBrief}")
            End If
        End Sub
    End Class
End Namespace
Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

See Also