Examples - OPC UA Services - Lock and unlock a connection

.NET

C#
VB.NET

// This example shows how to lock and unlock connections to an OPC UA server. The component attempts to keep the locked
// connections open, until unlocked.
//
// 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 Microsoft.Extensions.DependencyInjection;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;
using OpcLabs.EasyOpc.UA.Services;

namespace UADocExamples._EasyUAClientConnectionControl
{
    class LockAndUnlockConnection
    {
        public static void Main1()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            // Instantiate the client object and hook events
            using (var client = new EasyUAClient())
            {
                // Obtain the client connection monitoring service.
                IEasyUAClientConnectionMonitoring clientConnectionMonitoring = client.GetService<IEasyUAClientConnectionMonitoring>();
                if (clientConnectionMonitoring is null)
                {
                    Console.WriteLine("The client connection monitoring service is not available.");
                    return;
                }

                // Obtain the client connection control service.
                IEasyUAClientConnectionControl clientConnectionControl = client.GetService<IEasyUAClientConnectionControl>();
                if (clientConnectionControl is null)
                {
                    Console.WriteLine("The client connection control service is not available.");
                    return;
                }

                // Display the server condition changed events.
                clientConnectionMonitoring.ServerConditionChanged += (sender, args) => Console.WriteLine(args);

                int lockHandle = 0;
                bool locked = false;
                try
                {
                    Console.WriteLine("Reading (1)");
                    // The first read will cause a connection to the server.
                    UAAttributeData attributeData1 =
                        client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853");
                    Console.WriteLine(attributeData1);

                    Console.WriteLine("Waiting for 10 seconds...");
                    // Since the connection is now not used for some time, and it is not locked, it will be closed.
                    System.Threading.Thread.Sleep(10 * 1000);

                    Console.WriteLine("Locking");
                    // Locking the connection causes it to open, if possible.
                    lockHandle = clientConnectionControl.LockConnection(endpointDescriptor);
                    locked = true;

                    Console.WriteLine("Waiting for 10 seconds...");
                    // The connection is locked, it will not be closed now.
                    System.Threading.Thread.Sleep(10 * 1000);

                    Console.WriteLine("Reading (2)");
                    UAAttributeData attributeData2 =
                        client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853");
                    Console.WriteLine(attributeData2);

                    Console.WriteLine("Waiting for 10 seconds...");
                    // The connection is still locked, it will not be closed now.
                    System.Threading.Thread.Sleep(10 * 1000);
                }
                catch (UAException uaException)
                {
                    Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                }
                finally
                {
                    if (locked)
                    {
                        Console.WriteLine("Unlocking");
                        clientConnectionControl.UnlockConnection(lockHandle);
                    }
                }

                Console.WriteLine("Waiting for 10 seconds...");
                // After some delay, the connection will be closed, because there are no subscriptions to the server and no
                // connection locks.
                System.Threading.Thread.Sleep(10 * 1000);

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


        // Example output:
        //
        //Reading (1)
        //"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success; Attempt #1
        //"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
        //-1.034588E+18 {Single} @2021-11-15T15:26:39.169 @@2021-11-15T15:26:39.169; Good
        //Waiting for 10 seconds...
        //"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
        //"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(RetrialDelay=Infinite); Success
        //Locking
        //"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success; Attempt #1
        //"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
        //Waiting for 10 seconds...
        //Reading (2)
        //2.288872E+21 {Single} @2021-11-15T15:26:59.836 @@2021-11-15T15:26:59.836; Good
        //Waiting for 10 seconds...
        //Unlocking
        //Waiting for 10 seconds...
        //"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
        //"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(RetrialDelay=Infinite); Success
        //Finished.
    }
}

' This example shows how to lock and unlock connections to an OPC UA server. The component attempts to keep the locked
' connections open, until unlocked.
'
' 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 Microsoft.Extensions.DependencyInjection
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel
Imports OpcLabs.EasyOpc.UA.Services

Namespace _EasyUAClientConnectionControl
    Partial Friend Class LockAndUnlockConnection
        Public Shared Sub Main1()
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object and hook events
            Using client = New EasyUAClient()
                ' Obtain the client connection monitoring service.
                Dim clientConnectionMonitoring As IEasyUAClientConnectionMonitoring = client.GetService(Of IEasyUAClientConnectionMonitoring)
                If clientConnectionMonitoring Is Nothing Then
                    Console.WriteLine("The client connection monitoring service is not available.")
                    Exit Sub
                End If

                ' Obtain the client connection control service.
                Dim clientConnectionControl As IEasyUAClientConnectionControl = client.GetService(Of IEasyUAClientConnectionControl)
                If clientConnectionControl Is Nothing Then
                    Console.WriteLine("The client connection control service is not available.")
                    Exit Sub
                End If

                ' Display the server condition changed events.
                AddHandler clientConnectionMonitoring.ServerConditionChanged, Sub(sender, args)
                                                                                  Console.WriteLine(args)
                                                                              End Sub

                Dim lockHandle As Integer = 0
                Dim locked As Boolean = False
                Try
                    Console.WriteLine("Reading (1)")
                    ' The first read will cause a connection to the server.
                    Dim attributeData1 As UAAttributeData =
                        client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853")
                    Console.WriteLine(attributeData1)

                    Console.WriteLine("Waiting for 10 seconds...")
                    ' Since the connection is now not used for some time, and it is not locked, it will be closed.
                    System.Threading.Thread.Sleep(10 * 1000)

                    Console.WriteLine("Locking")
                    ' Locking the connection causes it to open, if possible.
                    lockHandle = clientConnectionControl.LockConnection(endpointDescriptor)
                    locked = True

                    Console.WriteLine("Waiting for 10 seconds...")
                    ' The connection is locked, it will not be closed now.
                    System.Threading.Thread.Sleep(10 * 1000)

                    Console.WriteLine("Reading (2)")
                    Dim attributeData2 As UAAttributeData =
                        client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853")
                    Console.WriteLine(attributeData2)

                    Console.WriteLine("Waiting for 10 seconds...")
                    ' The connection is still locked, it will not be closed now.
                    System.Threading.Thread.Sleep(10 * 1000)
                Catch uaException As UAException
                    Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message)
                Finally
                    If locked Then
                        Console.WriteLine("Unlocking")
                        clientConnectionControl.UnlockConnection(lockHandle)
                    End If
                End Try

                Console.WriteLine("Waiting for 10 seconds...")
                ' After some delay, the connection will be closed, because there are no subscriptions to the server and no
                ' connection locks.
                System.Threading.Thread.Sleep(10 * 1000)

                Console.WriteLine("Finished.")
            End Using
        End Sub

        ' Example output
        '
        'Reading (1)
        '"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success; Attempt #1
        '"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
        '-1.034588E+18 {Single} @2021-11-15T15:26:39.169 @@2021-11-15T15:26:39.169; Good
        'Waiting for 10 seconds...
        '"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
        '"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(RetrialDelay=Infinite); Success
        'Locking
        '"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success; Attempt #1
        '"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
        'Waiting for 10 seconds...
        'Reading (2)
        '2.288872E+21 {Single} @2021-11-15T15:26:59.836 @@2021-11-15T15:26:59.836; Good
        'Waiting for 10 seconds...
        'Unlocking
        'Waiting for 10 seconds...
        '"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
        '"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(RetrialDelay=Infinite); Success
        'Finished.
    End Class
End Namespace

COM

VBScript

Rem This example shows how to lock and unlock connections to an OPC UA server. The component attempts to keep the locked
Rem connections open, until unlocked.
Rem
Rem Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
Rem OPC client and subscriber examples in VBScript on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBScript .
Rem Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
Rem a commercial license in order to use Online Forums, and we reply to every post.

Option Explicit

Dim endpointDescriptorUrlString: endpointDescriptorUrlString = "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
Dim EndpointDescriptor: Set EndpointDescriptor = CreateObject("OpcLabs.EasyOpc.UA.UAEndpointDescriptor")
EndpointDescriptor.UrlString = endpointDescriptorUrlString

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

' Obtain the client connection monitoring service.
Dim ClientConnectionMonitoring: Set ClientConnectionMonitoring = Client.GetServiceByName("OpcLabs.EasyOpc.UA.Services.IEasyUAClientConnectionMonitoring, OpcLabs.EasyOpcUA")
If ClientConnectionMonitoring Is Nothing Then
    WScript.Echo "The client connection monitoring service is not available."
    WScript.Quit
End If

' Obtain the client connection control service.
Dim ClientConnectionControl: Set ClientConnectionControl = Client.GetServiceByName("OpcLabs.EasyOpc.UA.Services.IEasyUAClientConnectionControl, OpcLabs.EasyOpcUA")
If ClientConnectionControl Is Nothing Then
    WScript.Echo "The client connection control service is not available."
    WScript.Quit
End If

' Display the server condition changed events.
WScript.ConnectObject ClientConnectionMonitoring, "ClientConnectionMonitoring_"

WScript.Echo "Reading (1)"
' The first read will cause a connection to the server.
Dim AttributeData1: Set AttributeData1 = Client.Read(endpointDescriptorUrlString, "nsu=http://test.org/UA/Data/ ;i=10853")
WScript.Echo AttributeData1

WScript.Echo "Waiting for 10 seconds..."
' Since the connection is now not used for some time, and it is not locked, it will be closed.
WScript.Sleep 10*1000

WScript.Echo "Locking..."
' Locking the connection causes it to open, if possible.
Dim lockHandle: lockHandle = ClientConnectionControl.LockConnection(EndpointDescriptor)

WScript.Echo "Waiting for 10 seconds..."
' The connection is locked, it will not be closed now.
WScript.Sleep 10*1000

WScript.Echo "Reading (2)"
' The second read, because it closely follows the first one, will reuse the connection that is already open.
Dim AttributeData2: Set AttributeData2 = Client.Read(endpointDescriptorUrlString, "nsu=http://test.org/UA/Data/ ;i=10853")
WScript.Echo AttributeData2

WScript.Echo "Waiting for 10 seconds..."
' The connection is still locked, it will not be closed now.
WScript.Sleep 10*1000

WScript.Echo "Unlocking..."
ClientConnectionControl.UnlockConnection(lockHandle)

WScript.Echo "Waiting for 10 seconds..."
' After some delay, the connection will be closed, because there are no subscriptions to the server and no
' connection locks.
WScript.Sleep 10*1000

WScript.Echo "Finished."



Sub ClientConnectionMonitoring_ServerConditionChanged(Sender, e)
    WScript.Echo e
End Sub


' Example output:
'
'Reading (1)
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success; Attempt #1
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
'-1.034588E+18 {Single} @2021-11-15T15:26:39.169 @@2021-11-15T15:26:39.169; Good
'Waiting for 10 seconds...
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(RetrialDelay=Infinite); Success
'Locking
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success; Attempt #1
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
'Waiting for 10 seconds...
'Reading (2)
'2.288872E+21 {Single} @2021-11-15T15:26:59.836 @@2021-11-15T15:26:59.836; Good
'Waiting for 10 seconds...
'Unlocking
'Waiting for 10 seconds...
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(RetrialDelay=Infinite); Success
'Finished.

Python

Python (.NET)

# This example shows how to lock and unlock connections to an OPC UA server. The component attempts to keep the locked
# connections open, until unlocked.
#
# 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 time
import opclabs_quickopc

# Import .NET namespaces.
from Microsoft.Extensions.DependencyInjection import *
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.OperationModel import *
from OpcLabs.EasyOpc.UA.Services import *


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object and hook events.
client = None
try:
    client = EasyUAClient()

    # Obtain the client connection monitoring service.
    clientConnectionMonitoring = ServiceProviderServiceExtensions.GetService[IEasyUAClientConnectionMonitoring](client)
    if clientConnectionMonitoring is None:
        print('The client connection monitoring service is not available.')
        exit()

    # Obtain the client connection control service.
    clientConnectionControl = ServiceProviderServiceExtensions.GetService[IEasyUAClientConnectionControl](client)
    if clientConnectionControl is None:
        print('The client connection control service is not available.')
        exit()

    # Display the server condition changed events.
    clientConnectionMonitoring.ServerConditionChanged += lambda sender, args: print(args)

    lockHandle = 0
    locked = False
    try:
        print('Reading (1)')
        # The first read will cause a connection to the server.
        attributeData1 = IEasyUAClientExtension.Read(client,
                                                     endpointDescriptor,
                                                     UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'))
        print(attributeData1)

        print('Waiting for 10 seconds...')
        # Since the connection is now not used for some time, and it is not locked, it will be closed.
        time.sleep(10)

        print('Locking')
        # Locking the connection causes it to open, if possible.
        lockHandle = clientConnectionControl.LockConnection(endpointDescriptor)
        locked = True

        print('Waiting for 10 seconds...')
        # The connection is locked, it will not be closed now.
        time.sleep(10)

        print('Reading (2)')
        attributeData2 = IEasyUAClientExtension.Read(client,
                                                     endpointDescriptor,
                                                     UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'))
        print(attributeData2)

        print('Waiting for 10 seconds...')
        # The connection is still locked, it will not be closed now.
        time.sleep(10)

    except UAException as uaException:
        print('*** Failure: ' + uaException.GetBaseException().Message)

    finally:
        if locked:
            print('Unlocking')
            clientConnectionControl.UnlockConnection(lockHandle)

    print('Waiting for 10 seconds...')
    # After some delay, the connection will be closed, because there are no subscriptions to the server and no
    # connection locks.
    time.sleep(10)

    print('Finished.')

finally:
    client and client.Dispose()

Examples - Client OPC Unified Architecture

Examples - OPC Unified Architecture - Read a single value

Concepts

OPC Data Client Component Services

OPC Data Client Operation Control Services

OPC Data Client Operation Monitoring Services