Examples - OPC Data Access - Isolated client objects

.NET

C#
VB.NET

// This example shows how to create and use two isolated client objects, resulting in two separate connections to the target
// OPC DA server.
//
// 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.Threading;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    class Isolated
    {
        public static void Main1()
        {
            // Instantiate the client objects and make them isolated
            var client1 = new EasyDAClient { Isolated = true };
            var client2 = new EasyDAClient { Isolated = true };

            // The callback is a local method the displays the value
            void ItemChangedCallback(object sender, EasyDAItemChangedEventArgs eventArgs)
            {
                Debug.Assert(!(eventArgs is null));

                string displayPrefix = $"[{eventArgs.Arguments.State}]";
                if (eventArgs.Succeeded)
                {
                    Debug.Assert(!(eventArgs.Vtq is null));
                    Console.WriteLine($"{displayPrefix} {eventArgs.Vtq}");
                }
                else
                    Console.WriteLine($"{displayPrefix} *** Failure: {eventArgs.ErrorMessageBrief}");
            }

            Console.WriteLine("Subscribing...");
            client1.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, ItemChangedCallback, state: 1);
            client2.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, ItemChangedCallback, state: 2);

            Console.WriteLine("Processing item changed events for 10 seconds...");
            Thread.Sleep(10 * 1000);

            Console.WriteLine("Unsubscribing...");
            client1.UnsubscribeAllItems();
            client2.UnsubscribeAllItems();

            Console.WriteLine("Waiting for 2 seconds...");
            Thread.Sleep(2 * 1000);
        }
    }
}

' This example shows how to create and use two isolated client objects, resulting in two separate connections to the target
' OPC DA server.
'
' 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.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class Isolated
        Shared Sub Main1()
            ' Instantiate the client objects and make them isolated
            Dim client1 As New EasyDAClient() With {.Isolated = True}
            Dim client2 As New EasyDAClient() With {.Isolated = True}

            ' The callback is a local method the displays the value
            Dim ItemChagedCallback = Sub(sender As Object, eventArgs As EasyDAItemChangedEventArgs)
                                         Debug.Assert(eventArgs IsNot Nothing)

                                         Dim displayPrefix As String = $"[{eventArgs.Arguments.State}]"
                                         If eventArgs.Succeeded Then
                                             Debug.Assert(eventArgs.Vtq IsNot Nothing)
                                             Console.WriteLine($"{displayPrefix} {eventArgs.Vtq}")
                                         Else
                                             Console.WriteLine($"{displayPrefix} *** Failure: {eventArgs.ErrorMessageBrief}")
                                         End If
                                     End Sub

            Console.WriteLine("Subscribing...")
            client1.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, ItemChagedCallback, state:=1)
            client2.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, ItemChagedCallback, state:=2)

            Console.WriteLine("Processing item changed events for 10 seconds...")
            Threading.Thread.Sleep(10 * 1000)

            Console.WriteLine("Unsubscribing...")
            client1.UnsubscribeAllItems()
            client2.UnsubscribeAllItems()

            Console.WriteLine("Waiting for 2 seconds...")
            Threading.Thread.Sleep(2 * 1000)
        End Sub
    End Class
End Namespace

Python

Python (.NET)

# This example shows how to create and use two isolated client objects, resulting in two separate connections to the
# target OPC DA server.
#
# 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.DataAccess import *


# Item changed event handler
def itemChangedCallback(sender, eventArgs):
    assert eventArgs is not None
    displayPrefix = '[{}]'.format(eventArgs.Arguments.State)
    if eventArgs.Succeeded:
        assert eventArgs.Vtq is not None
        print(displayPrefix + ' ' + eventArgs.Vtq.ToString() + '\n', end='')
    else:
        print(displayPrefix + ' *** Failure: ' + eventArgs.ErrorMessageBrief + '\n', end='')


# Instantiate the client objects and make them isolated.
client1 = EasyDAClient()
client1.Isolated = True
client2 = EasyDAClient()
client2.Isolated = True

print('Subscribing item changes...')
IEasyDAClientExtension.SubscribeItem(client1,
                                     '', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000,
                                     EasyDAItemChangedEventHandler(itemChangedCallback), 1)
IEasyDAClientExtension.SubscribeItem(client2,
                                     '', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000,
                                     EasyDAItemChangedEventHandler(itemChangedCallback), 2)

print('Processing item change notifications for 10 seconds...')
time.sleep(10)

print('Unsubscribing all items...')
client1.UnsubscribeAllItems()
client2.UnsubscribeAllItems()

print('Waiting for 2 seconds...')
time.sleep(2)

print('Finished.')

Fundamentals

Isolated Clients and Subscribers