Tutorial

Getting started

• ClientClient.Temperature

  This sample demonstrates how to connect to an OPC UA server and read the value of a node once per second.

  C#VB.NET
• ServerServer.Temperature

  This sample demonstrates how to setup an OPC UA server that provides a temperature node and updates its value once per second.

  C#VB.NET

Repository on GitHub

Start the server first, then the client in a second terminal.

git clone https://github.com/Traeger-GmbH/opcuanet-samples.git
cd opcuanet-samples
dotnet run --project cs/Scenarios/Server.Temperature -f net8.0
dotnet run --project cs/Scenarios/Client.Temperature -f net8.0

Prerequisites

• Target framework: .NET or .NET Framework 4.7.2 or later, all supported frameworks under Target frameworks
• NuGet package: Opc.UaFx.Client, for OPC Classic Opc.UaFx.Advanced (Downloads)
• OPC UA server: a reachable server, for first tests for example the server from the complete example of server development
• License: not required for the evaluation. Without a license key, the SDK runs with its full feature set, limited to 30 minutes per application launch (Set up the license)

Connect to an OPC UA server

1. Add a reference to the client namespace Opc.UaFx.Client:

C#

using Opc.UaFx.Client;

VB.NET

Imports Opc.UaFx.Client

2. Create an instance of the OpcClient class with the address of the server:

C#

var client = new OpcClient("opc.tcp://localhost:4840/");

VB.NET

Dim client = New OpcClient("opc.tcp://localhost:4840/")

3. Connect to the server and start the session:

C#

client.Connect();

VB.NET

client.Connect()

4. Work with the server (your code):

C#

// Your code to interact with the server.

VB.NET

'Your code to interact with the server.

5. Disconnect before the application exits:

C#

client.Disconnect();

VB.NET

client.Disconnect()

6. With a using block, it looks like this:

C#

using (var client = new OpcClient("opc.tcp://localhost:4840/")) {
    client.Connect();
    // Your code to interact with the server.
}

VB.NET

Using client As New OpcClient("opc.tcp://localhost:4840/")
    client.Connect()
    'Your code to interact with the server.
End Using

How you continue depends on whether you know the nodes and NodeIds of the server:

• Unknown: The section Explore the address space shows which nodes the server provides.
• Known: Read values or Write values

Find servers

Types usedOpcDiscoveryClientOpcApplicationDescription

If you do not know the address of a server, a discovery server (for example the Local Discovery Server on port 4840) returns the servers registered with it, along with their discovery addresses. For each server, DiscoverServers returns its name, its type, and its addresses. An overload of DiscoverServers restricts the result to servers with specific application URIs, and an overload of DiscoverEndpoints restricts it to endpoints with specific transport profiles. To find out which endpoints a server offers, continue with the section Choose a secure endpoint:

C#

using (var discovery = new OpcDiscoveryClient("opc.tcp://localhost:4840/")) {
    foreach (OpcApplicationDescription server in discovery.DiscoverServers()) {
        Console.WriteLine("{0} ({1})", server.Name, server.Type);
 
        foreach (Uri url in server.DiscoveryUrls)
            Console.WriteLine("  {0}", url);
    }
}

VB.NET

Using discovery = New OpcDiscoveryClient("opc.tcp://localhost:4840/")
    For Each server As OpcApplicationDescription In discovery.DiscoverServers()
        Console.WriteLine("{0} ({1})", server.Name, server.Type)

        For Each url As Uri In server.DiscoveryUrls
            Console.WriteLine("  {0}", url)
        Next
    Next
End Using

Connect to an OPC Classic server

To connect to an OPC Classic server, the client must run on Windows, and the OPC Classic runtime must be installed on the computer. Support for OPC Classic is only included in the Opc.UaFx.Advanced package.

The page OPC Classic describes what you can do after connecting to a Classic server (DA, AE, and HDA with the same API).

1. Add references to the Classic and client namespaces:

C#

using Opc.UaFx.Client;
using Opc.UaFx.Client.Classic;

VB.NET

Imports Opc.UaFx.Client
Imports Opc.UaFx.Client.Classic

2. Create an instance of the OpcClient class with the address of the server:

C#

var client = new OpcClient("opc.com://localhost:48410/<progId>/<classId>");

VB.NET

Dim client As New OpcClient("opc.com://localhost:48410/<progId>/<classId>")

3. Connect to the server and start the session:

C#

client.Connect();

VB.NET

client.Connect()

4. Work with the server (your code):

C#

// Your code to interact with the server.

VB.NET

'Your code to interact with the server.

5. Disconnect before the application exits:

C#

client.Disconnect();

VB.NET

client.Disconnect()

6. With a using block, it looks like this:

C#

using (var client = new OpcClient("opc.com://localhost:48410/<progId>/<classId>")) {
    client.Connect();
    // Your code to interact with the server.
}

VB.NET

Using client As New OpcClient("opc.com://localhost:48410/<progId>/<classId>")
    client.Connect()
    'Your code to interact with the server.
End Using

How you continue depends on whether you know the nodes and NodeIds of the server:

• Unknown: The section Explore the address space shows which nodes the server provides.
• Known: Read values or Write values

The address of the server is structured like this: opc.com://localhost:48410/<progId>/<classId>

• opc.com states that the client connects to an OPC Classic server.
• localhost stands for the name or IP address of the computer on which the OPC Classic server runs.
• 48410 is the optional port number that the OPC UA wrapper server^[1] uses. If you omit it, the wrapper server uses a free port assigned by the system.
• <progId> is an optional placeholder. Replace it with the ProgID from the DCOM application information of the OPC Classic server, for example OPCManager.DA.XML-DA.Server.DA. The address opc.com://localhost/<classId> without <progId> works as well.
• <classId> is a placeholder. Replace it with the ClassId (also CLSID or AppID) from the DCOM application information of the OPC Classic server, for example {E4EBF7FA-CCAC-4125-A611-EAC4981C00EA}. You must specify the ClassId as a GUID.

Determine the <classId> or <progId> of the server:

Method: OpcClassicDiscoveryClient

C#

using (var discoveryClient = new OpcClassicDiscoveryClient("<host>")) {
    var servers = discoveryClient.DiscoverServers();

    foreach (var server in servers) {
        Console.WriteLine(
                "- {0}, ClassId={1}, ProgId={2}",
                server.Name,
                server.ClassId,
                server.ProgId);
    }
}

VB.NET

Using discoveryClient As New OpcClassicDiscoveryClient("<host>")
    Dim servers = discoveryClient.DiscoverServers()

    For Each server In servers
        Console.WriteLine( _
                "- {0}, ClassId={1}, ProgId={2}", _
                server.Name, _
                server.ClassId, _
                server.ProgId)
    Next
End Using

Method: system information. Perform the following steps on the computer of the OPC Classic server:

1. Determine the AppID in Component Services
   • Control Panel
   • Administrative Tools
   • Component Services
   • Expand "Component Services"
   • Expand "Computers"
   • Expand "My Computer"
   • Expand "DCOM Config"
   • Select <OPC Classic Server>
   • Open "Properties"
   • First tab "General"
   • Copy "Application ID:", which is the AppID
2. Determine the ProgId in the system registry
   • "Windows key" + "R"
   • Type regedit
   • Click "OK"
   • Expand the "Computer" key
   • Then the "HKEY_LOCAL_MACHINE" key
   • Expand "SOFTWARE"
   • Expand "WOW6432Node" (only on 64-bit systems, otherwise skip this step)
   • Expand "Classes"
   • Expand "CLSID"
   • Expand <classId>
   • Select ProgID
   • Copy the value "(Default)" in the "Data" column, which is the ProgID

Complete example

Complete program: a client that connects to a server and reads a temperature node once per second:

C#

namespace Client
{
    using System;
    using System.Threading;

    using Opc.UaFx.Client;

    /// <summary>
    /// This sample demonstrates how to connect to an OPC UA server and read the value of a node
    /// once per second.
    /// </summary>
    public class Program
    {
        public static void Main()
        {
            using (var client = new OpcClient("opc.tcp://localhost:4840")) {
                client.Connect();

                while (true) {
                    var temperature = client.ReadNode("ns=2;s=Temperature");
                    Console.WriteLine("Current Temperature is {0} °C", temperature);

                    Thread.Sleep(1000);
                }
            }
        }
    }
}

VB.NET

Imports System
Imports System.Threading

Imports Opc.UaFx.Client

Namespace Client
    ''' <summary>
    ''' This sample demonstrates how to connect to an OPC UA server and read the value of a node
    ''' once per second.
    ''' </summary>
    Public Class Program
        Public Shared Sub Main()
            Using client = New OpcClient("opc.tcp://localhost:4840")
                client.Connect()

                While True
                    Dim temperature = client.ReadNode("ns=2;s=Temperature")
                    Console.WriteLine("Current Temperature is {0} °C", temperature)

                    Thread.Sleep(1000)
                End While
            End Using
        End Sub
    End Class
End Namespace

If the server from the complete example of server development runs on the same computer, the client prints a line Current Temperature is … °C once per second. The value rises from 100 to 110 and then starts again at 100.

Next steps

How-to guide

Browse nodes

Explore the address space of a server: node by node from the ObjectsFolder, or several levels in one pass.

→

How-to guide

Read and write values

Read and write the values of single and multiple nodes, access other attributes and parts of arrays, and evaluate the results with their status.

→

How-to guide

Subscriptions

Subscribe to value changes and events of nodes, handle notifications, manage subscriptions, and narrow them down with filters.

→

How-to guide

Secure clients

Secure the client: choose an endpoint, validate server certificates, protect your own certificate, authenticate users, and use a checklist for production.

→

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1. The OPC UA client starts the OPC UA wrapper server automatically and stops it when it disconnects. Each client starts its own wrapper server. The OPC UA wrapper server wraps the requests of the OPC UA client and sends them to the OPC Classic server. The OPC UA wrapper server sends the responses of the OPC Classic server back to the OPC UA client as OPC UA responses. ↩︎