OPC Studio User's Guide and Reference
IEasyUASubscriber Interface
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OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA.PubSub Namespace : IEasyUASubscriber Interface
Provides easy OPC UA PubSub subscriber functionality.
Syntax
'Declaration
 
<ComVisibleAttribute(False)>
<ExceptionContractAnnotationAttribute(True)>
<ExceptionContractVerificationAttribute(True)>
Public Interface IEasyUASubscriber 
   Inherits System.IServiceProvider 
 
'Usage
 
Dim instance As IEasyUASubscriber
Remarks

Defines the interface for a subscriber in the OPC UA PubSub communication model. This interface provides the necessary methods for managing subscriptions to OPC UA published data. Provides creation, maintenance, and disposal of subscriptions, and facilitates the reception of published data from OPC UA publishers.

 

This chapter gives guidance in implementing common tasks when dealing with data made available over OPC UA PubSub. You achieve these tasks mainly by calling methods on the EasyUASubscriber object. Depending on what you need, see:

Subscribing to Information (OPC UA PubSub)
The features discussed here, or some of them, may not be available in all editions of the product. Check the QuickOPC Product Editions page for differences between the editions. The trial license has all features enabled (and is limited in period for which it provides valid data), but licenses for specific commercial editions may have functionality limitations.

OPC UA PubSub is a large specification, and not all its parts are commonly used and have the same significance. QuickOPC implements the parts that are relevant for its purpose. Some parts OPC UA PubSub functionality is not available in QuickOPC. The parts that are not (yet) available include:

Most of the OPC UA PubSub examples work with the OPC UA Demo Publisher that is installed with the product, or can be downloaded separately. It supports Windows, Linux and macOS.

 

Example
// This example shows how to subscribe to all dataset messages on an OPC-UA PubSub connection with UDP UADP mapping.
//
// In order to produce network messages for this example, run the UADemoPublisher tool. For documentation, see
// https://kb.opclabs.com/UADemoPublisher_Basics . In some cases, you may have to specify the interface name to be used.
//
// 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.Collections.Generic;
using System.Threading;
using OpcLabs.EasyOpc.UA.PubSub;
using OpcLabs.EasyOpc.UA.PubSub.OperationModel;

namespace UASubscriberDocExamples.PubSub._EasyUASubscriber
{
    partial class SubscribeDataSet
    {
        public static void Main1()
        {
            // Define the PubSub connection we will work with. Uses implicit conversion from a string.
            UAPubSubConnectionDescriptor pubSubConnectionDescriptor = "opc.udp://239.0.0.1";
            // In some cases you may have to set the interface (network adapter) name that needs to be used, similarly to
            // the statement below. Your actual interface name may differ, of course.
            //pubSubConnectionDescriptor.ResourceAddress.InterfaceName = "Ethernet";

            // Instantiate the subscriber object and hook events.
            var subscriber = new EasyUASubscriber();
            subscriber.DataSetMessage += subscriber_DataSetMessage;

            Console.WriteLine("Subscribing...");
            subscriber.SubscribeDataSet(pubSubConnectionDescriptor);

            Console.WriteLine("Processing dataset message events for 20 seconds...");
            Thread.Sleep(20 * 1000);

            Console.WriteLine("Unsubscribing...");
            subscriber.UnsubscribeAllDataSets();

            Console.WriteLine("Waiting for 1 second...");
            // Unsubscribe operation is asynchronous, messages may still come for a short while.
            Thread.Sleep(1 * 1000);

            Console.WriteLine("Finished.");
        }

        static void subscriber_DataSetMessage(object sender, EasyUADataSetMessageEventArgs e)
        {
            // Display the dataset.
            if (e.Succeeded)
            {
                // An event with null DataSetData just indicates a successful connection.
                if (!(e.DataSetData is null))
                {
                    Console.WriteLine();
                    Console.WriteLine($"Dataset data: {e.DataSetData}");
                    foreach (KeyValuePair<string, UADataSetFieldData> pair in e.DataSetData.FieldDataDictionary)
                        Console.WriteLine(pair);
                }
            }
            else
            {
                Console.WriteLine();
                Console.WriteLine($"*** Failure: {e.ErrorMessageBrief}");
            }
        }


        // Example output (truncated):
        //
        //Subscribing...
        //Processing dataset message events for 20 seconds...
        //
        //Dataset data: Good; Data; publisher="32", writer=1, class=eae79794-1af7-4f96-8401-4096cd1d8908, fields: 4
        //[#0, True {System.Boolean} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#1, 7945 {System.Int32} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#2, 5246 {System.Int32} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#3, 9/30/2019 11:19:14 AM {System.DateTime} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //
        //Dataset data: Good; Data; publisher="32", writer=3, class=96976b7b-0db7-46c3-a715-0979884b55ae, fields: 100
        //[#0, 45 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#1, 145 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#2, 245 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#3, 345 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#4, 445 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#5, 545 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#6, 645 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#7, 745 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#8, 845 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#9, 945 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#10, 1045 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //...
    }
}
# This example shows how to subscribe to all dataset messages on an OPC-UA PubSub connection, and pull events, and display
# the incoming datasets.
#
# In order to produce network messages for this example, run the UADemoPublisher tool. For documentation, see
# https://kb.opclabs.com/UADemoPublisher_Basics . In some cases, you may have to specify the interface name to be used.
#
# The Python for Windows (pywin32) extensions package is needed. Install it using "pip install pypiwin32".
# CAUTION: We now recommend using Python.NET package instead. Full set of examples with Python.NET is available!
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
import time
import win32com.client

# Define the PubSub connection we will work with.
subscribeDataSetArguments = win32com.client.Dispatch('OpcLabs.EasyOpc.UA.PubSub.OperationModel.EasyUASubscribeDataSetArguments')
connectionDescriptor = subscribeDataSetArguments.DataSetSubscriptionDescriptor.ConnectionDescriptor
connectionDescriptor.ResourceAddress.ResourceDescriptor.UrlString = 'opc.udp://239.0.0.1'
# In some cases you may have to set the interface (network adapter) name that needs to be used, similarly to
# the statement below. Your actual interface name may differ, of course.
#connectionDescriptor.ResourceAddress.InterfaceName = 'Ethernet'

# Instantiate the subscriber object.
subscriber = win32com.client.Dispatch('OpcLabs.EasyOpc.UA.PubSub.EasyUASubscriber') 
# In order to use event pull, you must set a non-zero queue capacity upfront.
subscriber.PullDataSetMessageQueueCapacity = 1000

print('Subscribing...')
subscriber.SubscribeDataSet(subscribeDataSetArguments)

print('Processing dataset message events for 20 seconds...')
endTime = time.time() + 20
while time.time() < endTime:
    eventArgs = subscriber.PullDataSetMessage(2*1000)
    if eventArgs is not None:
        # Display the dataset.
        if eventArgs.Succeeded:
            # An event with null DataSetData just indicates a successful connection.
            if eventArgs.DataSetData is not None:
                print('')
                print('Dataset data: ', eventArgs.DataSetData)
                for pair in eventArgs.DataSetData.FieldDataDictionary:
                    print(pair)
        else:
            print('')
            print('*** Failure: ', eventArgs.ErrorMessageBrief)

print('Unsubscribing...')
subscriber.UnsubscribeAllDataSets

print('Waiting for 1 second...')
# Unsubscribe operation is asynchronous, messages may still come for a short while.
endTime = time.time() + 1
while time.time() < endTime:
    pass

print('Finished.')



# Example output:
#
#Subscribing...
#Processing dataset message events for 20 seconds...
#
##Dataset data: Good; Data; publisher="32", writer=1, class=eae79794-1af7-4f96-8401-4096cd1d8908, fields: 4
#[#0, True {System.Boolean} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#1, 7945 {System.Int32} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#2, 5246 {System.Int32} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#3, 9/30/2019 11:19:14 AM {System.DateTime} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#
#Dataset data: Good; Data; publisher="32", writer=3, class=96976b7b-0db7-46c3-a715-0979884b55ae, fields: 100
#[#0, 45 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#1, 145 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#2, 245 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#3, 345 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#4, 445 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#5, 545 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#6, 645 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#7, 745 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#8, 845 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#9, 945 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#[#10, 1045 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
#...
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