Uni.UaClient 1.0.4

opc-ua-client

Communicate using OPC Unified Architecture and Visual Studio. With this library, your app can browse, read, write and subscribe to the live data published by the OPC UA servers on your network.

Supports .NET Core, Universal Windows Platform (UWP), Windows Presentation Framework (WPF) and Xamarin applications.

Industrial Resilient Client (Out-of-the-Box 24×7)

For mission-critical shop floor, SCADA, and background services, use Uni.UaClient.Resilient.OpcClient. It encapsulates automatic reconnection with exponential backoff, single-flight session concurrency locks, non-intrusive industrial network probes, self-healing subscriptions, and PLC handshakes:

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Uni.UaClient.Resilient;
using Uni.UaClient.Resilient.Operations;
using Uni.UaClient.Resilient.Options;

// 1. Configure and connect
await using var client = new OpcClient(new OpcClientOptions
{
    EndpointUrl = "opc.tcp://192.168.1.100:4840",
    AutoReconnect = true,
    ReconnectBaseDelay = TimeSpan.FromSeconds(1),
    ReconnectMaxDelay = TimeSpan.FromSeconds(30)
});
await client.ConnectAsync();

// 2. Strongly-typed read and write
double speed = await client.ReadNodeAsync<double>("ns=2;s=Line1.Speed");
await client.WriteNodeAsync("ns=2;s=Line1.SetPoint", 1500.0);

// 3. Self-healing subscriptions with System.Threading.Channels decoupling
var sub = client.CreateSubscription(publishingInterval: 250);
await sub.AddNodeAsync("ns=2;s=Line1.Trigger", (nodeId, dataValue, _) =>
{
    Console.WriteLine($"[Update] {nodeId} = {dataValue.Value}");
    return Task.CompletedTask;
});

// 4. Closed-loop PLC handshake (Write Request -> Wait Condition -> Auto Reset)
var result = await client.HandshakeAsync(new HandshakeRequest
{
    RequestNodes = new Dictionary<string, object> { ["ns=2;s=Machine.Trigger"] = 1 },
    ResponseNodeId = "ns=2;s=Machine.Feedback",
    Condition = val => Convert.ToInt32(val.Value) == 2,
    ResetNodes = new Dictionary<string, object> { ["ns=2;s=Machine.Trigger"] = 0 },
    AlwaysResetOnFailure = true,
    Timeout = TimeSpan.FromSeconds(5)
});

ASP.NET Core / Generic Host Dependency Injection:

services.AddResilientOpcClient(options =>
{
    options.EndpointUrl = "opc.tcp://192.168.1.100:4840";
    options.AutoReconnect = true;
});

Low-Level Session Channel (Getting Started)

Install package Uni.UaClient from Nuget to get the latest release for your hmi project.

Here's an example of reading the variable ServerStatus using the low-level ClientSessionChannel.

using System;
using System.Threading.Tasks;
using Uni.UaClient;
using Uni.UaClient.Channels;
					
public class Program
{
    /// <summary>
    /// Connects to server and reads the current ServerState. 
    /// </summary>
    public static async Task Main()
    {
        // describe this client application.
        var clientDescription = new ApplicationDescription
        {
            ApplicationName = "Uni.UaClient.FeatureTests",
            ApplicationUri = $"urn:{System.Net.Dns.GetHostName()}:Uni.UaClient.FeatureTests",
            ApplicationType = ApplicationType.Client
        };

        // create a 'ClientSessionChannel', a client-side channel that opens a 'session' with the server.
        var channel = new ClientSessionChannel(
            clientDescription,
            null, // no x509 certificates
            new AnonymousIdentity(), // no user identity
            "opc.tcp://opcua.umati.app:4840", // the public endpoint of the umati sample server.
            SecurityPolicyUris.None); // no encryption
        try
        {
            // try opening a session and reading a few nodes.
            await channel.OpenAsync();

            Console.WriteLine($"Opened session with endpoint '{channel.RemoteEndpoint.EndpointUrl}'.");
            Console.WriteLine($"SecurityPolicy: '{channel.RemoteEndpoint.SecurityPolicyUri}'.");
            Console.WriteLine($"SecurityMode: '{channel.RemoteEndpoint.SecurityMode}'.");
            Console.WriteLine($"UserIdentityToken: '{channel.UserIdentity}'.");

            // build a ReadRequest. See 'OPC UA Spec Part 4' paragraph 5.10.2
            var readRequest = new ReadRequest {
                // set the NodesToRead to an array of ReadValueIds.
                NodesToRead = new[] {
                    // construct a ReadValueId from a NodeId and AttributeId.
                    new ReadValueId {
                        // you can parse the nodeId from a string.
                        // e.g. NodeId.Parse("ns=2;s=Demo.Static.Scalar.Double")
                        NodeId = NodeId.Parse(VariableIds.Server_ServerStatus),
                        // variable class nodes have a Value attribute.
                        AttributeId = AttributeIds.Value
                    }
                }
            };
            // send the ReadRequest to the server.
            var readResult = await channel.ReadAsync(readRequest);

            // DataValue is a class containing value, timestamps and status code.
            // the 'Results' array returns DataValues, one for every ReadValueId.
            var serverStatus = readResult.Results[0].GetValueOrDefault<ServerStatusDataType>();

            Console.WriteLine("\nServer status:");
            Console.WriteLine("  ProductName: {0}", serverStatus.BuildInfo.ProductName);
            Console.WriteLine("  SoftwareVersion: {0}", serverStatus.BuildInfo.SoftwareVersion);
            Console.WriteLine("  ManufacturerName: {0}", serverStatus.BuildInfo.ManufacturerName);
            Console.WriteLine("  State: {0}", serverStatus.State);
            Console.WriteLine("  CurrentTime: {0}", serverStatus.CurrentTime);

            Console.WriteLine($"\nClosing session '{channel.SessionId}'.");
            await channel.CloseAsync();
        }
        catch(Exception ex)
        {
		 	 await channel.AbortAsync();
            Console.WriteLine(ex.Message);
        }
    }
}

// Server status:
//   ProductName: open62541 OPC UA Server
//   SoftwareVersion: 1.4.0-rc1
//   ManufacturerName: open62541
//   State: Running

Model, View, ViewModel (MVVM)

For HMI applications, you can use XAML bindings to connect your UI elements to live data.

First add a UaApplication instance and initialize it during startup:

public partial class App : Application
{
    private UaApplication application;

    protected override void OnStartup(StartupEventArgs e)
    {
        // Build and run an OPC UA application instance.
        this.application = new UaApplicationBuilder()
            .SetApplicationUri($"urn:{Dns.GetHostName()}:Uni.StatusHmi")
            .SetDirectoryStore($"{Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData)}\\Uni.StatusHmi\\pki")
            .SetIdentity(this.ShowSignInDialog)
            .Build();

        this.application.Run();

        // Create and show the main view.
        var view = new MainView();
        view.Show();
    }
	...
}

Then any view model can be transformed into a OPC UA subscription.

[Subscription(endpointUrl: "opc.tcp://localhost:48010", publishingInterval: 500, keepAliveCount: 20)]
public class MainViewModel : SubscriptionBase
{
    /// <summary>
    /// Gets the value of ServerServerStatus.
    /// </summary>
    [MonitoredItem(nodeId: "i=2256")]
    public ServerStatusDataType ServerServerStatus
    {
        get { return this.serverServerStatus; }
        private set { this.SetProperty(ref this.serverServerStatus, value); }
    }

    private ServerStatusDataType serverServerStatus;
}

Configure EndpointUrl at runtime (MVVM)

You can use a configuration file to replace all instances of an EndpointUrl at runtime. Use this approach to specify different endpoints for development versus production.

using Microsoft.Extensions.Configuration;

var config = new ConfigurationBuilder()
    .SetBasePath(Directory.GetCurrentDirectory())
    .AddJsonFile("appSettings.json", true)
    .Build();

var app = new UaApplicationBuilder()
    ...
    .AddMappedEndpoints(config)
    .Build();

[Subscription(endpointUrl: "MainPLC", publishingInterval: 500, keepAliveCount: 20)]
public class MainViewModel : SubscriptionBase
{
    /// <summary>
    /// Gets the value of ServerServerStatus.
    /// </summary>
    [MonitoredItem(nodeId: "i=2256")]
    public ServerStatusDataType ServerServerStatus
    {
        get { return this.serverServerStatus; }
        private set { this.SetProperty(ref this.serverServerStatus, value); }
    }

    private ServerStatusDataType serverServerStatus;
}

appSettings.json

{
  "MappedEndpoints": [
    {
      "RequestedUrl": "MainPLC",
      "Endpoint": {
        "EndpointUrl": "opc.tcp://192.168.1.100:48010",
        "SecurityPolicyUri": "http://opcfoundation.org/UA/SecurityPolicy#None"
      }
    }
  ]
}