Connectivity Software User's Guide and Reference
HostId Property (SparkplugHostDescriptor)
Example 



OpcLabs.EasySparkplug Assembly > OpcLabs.EasySparkplug Namespace > SparkplugHostDescriptor Class : HostId Property
Sparkplug host ID of the Sparkplug host application.
Syntax
'Declaration
 
<JetBrains.Annotations.NotNullAttribute()>
Public Property HostId As String
'Usage
 
Dim instance As SparkplugHostDescriptor
Dim value As String
 
instance.HostId = value
 
value = instance.HostId
[JetBrains.Annotations.NotNull()]
public string HostId {get; set;}
[JetBrains.Annotations.NotNull()]
public:
property String^ HostId {
   String^ get();
   void set (    String^ value);
}

Property Value

The value represents a Sparkplug host ID. It must be a string with valid UTF-8 characters except for the reserved characters of '+' (plus) and '#' (number sign).

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

The default value of this property is "" (String.Empty).

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

When this value is empty (which is the default), the component will auto-generate a host ID that is conformant with the Sparkplug syntactic rules. It also attempts to make it unique within the Sparkplug system.

Sparkplug edge nodes can be configured to use this host ID as the primary host application ID, and adjust their behavior based on the status of the primary host.

 

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 consume Sparkplug data while specifying own Sparkplug host application ID.
//
// 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 OpcLabs.EasySparkplug;
using OpcLabs.EasySparkplug.OperationModel;
using System;
using System.Collections.Generic;

namespace SparkplugDocExamples.Consumer._SparkplugHostDescriptor
{
    class HostId
    {
        public static void Main1()
        {
            // Note that the default port for the "mqtt" scheme is 1883.
            // The second parameter is the host ID of this Sparkplug host application. Other Sparkplug components can use
            // this host ID to detect whether the application is online or offline.
            var hostDescriptor = new SparkplugHostDescriptor("mqtt://localhost", "easyApplication");

            // Instantiate the consumer object.
            var consumer = new EasySparkplugConsumer();

            Console.WriteLine("Subscribing...");
            consumer.SubscribeEdgeNodePayload(hostDescriptor, "easyGroup", "easySparkplugDemo",
                (sender, eventArgs) =>
                {
                    // Handle different types of notifications.
                    Console.WriteLine();
                    switch (eventArgs.NotificationType)
                    {
                        case SparkplugNotificationType.Connect:
                            Console.WriteLine($"Connected to Sparkplug host, client ID: {eventArgs.ClientId}.");
                            break;
                        case SparkplugNotificationType.Disconnect:
                            Console.WriteLine("Disconnected from Sparkplug host.");
                            break;
                        case SparkplugNotificationType.Data:
                        case SparkplugNotificationType.Birth:
                            Console.WriteLine("Received birth or data message from Sparkplug host.");
                            // Display the metrics name and data for each metric delivered in the payload.
                            foreach (KeyValuePair<string, SparkplugMetricElement> pair in eventArgs.Payload)
                                Console.WriteLine($"{pair.Key}: {pair.Value.MetricData}");
                            break;
                        case SparkplugNotificationType.Death:
                            Console.WriteLine("Received death message from Sparkplug host.");
                            break;
                    }
                    if (!eventArgs.Succeeded)
                        Console.WriteLine($"*** Failure: {eventArgs.ErrorMessageBrief}");
                });

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

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

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

            Console.WriteLine("Finished.");
        }
    }
}
' This example shows how to consume Sparkplug data while specifying own Sparkplug host application ID.
'
' 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._SparkplugHostDescriptor
    Class HostId
        Public Shared Sub Main1()
            ' Note that the default port for the "mqtt" scheme is 1883.
            ' The second parameter is the host ID of this Sparkplug host application. Other Sparkplug components can use
            ' this host ID to detect whether the application is online or offline.
            Dim hostDescriptor = New SparkplugHostDescriptor("mqtt://localhost", "easyApplication")

            ' Instantiate the consumer object.
            Dim consumer = New EasySparkplugConsumer()

            Console.WriteLine("Subscribing...")
            consumer.SubscribeEdgeNodePayload(hostDescriptor, "easyGroup", "easySparkplugDemo",
                Sub(sender, eventArgs)
                    ' Handle different types of notifications.
                    Console.WriteLine()
                    Select Case eventArgs.NotificationType
                        Case SparkplugNotificationType.Connect
                            Console.WriteLine($"Connected to Sparkplug host, client ID: {eventArgs.ClientId}.")
                        Case SparkplugNotificationType.Disconnect
                            Console.WriteLine("Disconnected from Sparkplug host.")
                        Case SparkplugNotificationType.Data,
                            SparkplugNotificationType.Birth
                            Console.WriteLine("Received birth or data message from Sparkplug host.")
                            ' Display the metrics name and data for each metric delivered in the payload.
                            For Each pair As KeyValuePair(Of String, SparkplugMetricElement) In eventArgs.Payload
                                Console.WriteLine($"{pair.Key}: {pair.Value.MetricData}")
                            Next
                        Case SparkplugNotificationType.Death
                            Console.WriteLine("Received death message from Sparkplug host.")
                    End Select
                    If Not eventArgs.Succeeded Then
                        Console.WriteLine($"*** Failure: {eventArgs.ErrorMessageBrief}")
                    End If
                End Sub)

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

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

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

            Console.WriteLine("Finished.")
        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