Examples - Server OPC UA - Adjust to sampling interval changes in push model

.NET

C#
VB.NET

// This example shows how to adjust to sampling interval changes in the push data provision model.
// You can use any OPC UA client, including our Connectivity Explorer and OpcCmd utility, to connect to the server. 
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client, server and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-OPCStudio-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.Threading;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.NodeSpace;
using Timer = System.Timers.Timer;

namespace UAServerDocExamples._UAServerNode
{
    class SamplingIntervalChanged
    {
        public static void Main1()
        {
            // Instantiate the server object.
            // By default, the server will run on endpoint URL "opc.tcp://localhost:48040/".
            var server = new EasyUAServer();

            // Create a timer for pushing the data for OPC reads. In a real server the activity may also come from other
            // sources.
            var timer = new Timer { AutoReset = true };

            // Create a read-only data variable.
            var dataVariable = UADataVariable.CreateIn(server.Objects, "SubscribeToThisVariable")
                .ValueType<int>()
                .Writable(false);
            dataVariable.SamplingIntervalChanged += (sender, args) =>
            {
                // Obtain and display the new sampling interval.
                int samplingInterval = dataVariable.SamplingInterval;
                Console.WriteLine($"Sampling interval changed to: {samplingInterval}");

                // Adjust the timer interval accordingly. If the sampling interval is infinite, stop the timer. Otherwise,
                // set the timer interval to half of the sampling interval, but at least 1 millisecond, and start the timer.
                if (samplingInterval == Timeout.Infinite)
                    timer.Enabled = false;
                else
                {
                    timer.Interval = Math.Max(samplingInterval/2, 1);
                    timer.Enabled = true;
                }
                args.Handled = true;
            };
            
            // Set the read attribute data of the data variable to a random value whenever the timer interval elapses.
            var random = new Random();
            timer.Elapsed += (sender, args) => dataVariable.UpdateReadAttributeData(random.Next());

            // Start the server.
            Console.WriteLine("The server is starting...");
            server.Start();

            Console.WriteLine("The server is started.");
            Console.WriteLine();

            // Let the user decide when to stop.
            Console.WriteLine("Press Enter to stop the server...");
            Console.ReadLine();

            // Stop the server.
            Console.WriteLine("The server is stopping...");
            server.Stop();

            // Stop the timer.
            timer.Stop();

            Console.WriteLine("The server is stopped.");
        }
    }
}

' This example shows how to adjust to sampling interval changes in the push data provision model.
' You can use any OPC UA client, including our Connectivity Explorer and OpcCmd utility, to connect to the 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 System
Imports System.Threading
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.NodeSpace
Imports Timer = System.Timers.Timer

Namespace _UAServerNode
    Partial Friend Class SamplingIntervalChanged
        Shared Sub Main1()
            ' Instantiate the server object.
            ' By default, the server will run on endpoint URL "opc.tcp://localhost:48040/".
            Dim server = New EasyUAServer()

            ' Create a timer for pushing the data for OPC reads. In a real server the activity may also come from other
            ' sources.
            Dim timer = New Timer With {.AutoReset = True}

            ' Create a read-only data variable.
            Dim dataVariable = UADataVariable.CreateIn(server.Objects, "SubscribeToThisVariable") _
                .ValueType(Of Integer)() _
                .Writable(False)

            AddHandler dataVariable.SamplingIntervalChanged, Sub(sender, args)
                                                                 ' Obtain and display the new sampling interval.
                                                                 Dim samplingInterval As Integer = dataVariable.SamplingInterval
                                                                 Console.WriteLine($"Sampling interval changed to: {samplingInterval}")

                                                                 ' Adjust the timer interval accordingly. If the sampling interval is infinite, stop the timer. Otherwise,
                                                                 ' set the timer interval to half of the sampling interval, but at least 1 millisecond, and start the timer.
                                                                 If samplingInterval = Timeout.Infinite Then
                                                                     timer.Enabled = False
                                                                 Else
                                                                     timer.Interval = Math.Max(samplingInterval / 2, 1)
                                                                     timer.Enabled = True
                                                                 End If
                                                                 args.Handled = True
                                                             End Sub

            ' Set the read attribute data of the data variable to a random value whenever the timer interval elapses.
            Dim random = New Random()
            AddHandler timer.Elapsed, Sub(sender, args) dataVariable.UpdateReadAttributeData(random.Next())

            ' Start the server.
            Console.WriteLine("The server is starting...")
            server.Start()

            Console.WriteLine("The server is started.")
            Console.WriteLine()

            ' Let the user decide when to stop.
            Console.WriteLine("Press Enter to stop the server...")
            Console.ReadLine()

            ' Stop the server.
            Console.WriteLine("The server is stopping...")
            server.Stop()

            Console.WriteLine("The server is stopped.")
        End Sub
    End Class
End Namespace

Concepts

Custom Data Subscriptions

Push Data Provision Model