# OPC UA SDK for .NET

> Documentation of the OPC UA .NET SDK: develop OPC UA clients and servers in C# and VB.NET, with access to OPC Classic.

> This content was machine translated and may contain errors. [Read in German](https://www.traeger.de/docs/development/opcua/)

Develop OPC UA clients and servers in C# and VB.NET.

Latest version v2.59.0, released November 9, 2026 ([version history](https://www.traeger.de/en/docs/development/opcua/version-history)).

With the OPC UA .NET SDK, you connect .NET applications to OPC UA servers
and provide your own OPC UA servers. With the OPC Classic add-on, the same
client also accesses OPC DA, OPC HDA, and OPC AE servers.

## Install

The SDK is available as a NuGet package. For clients, `Opc.UaFx.Client` is
enough. For servers and for OPC Classic, use `Opc.UaFx.Advanced`:

```sh
dotnet add package Opc.UaFx.Client
```

```sh
dotnet add package Opc.UaFx.Advanced
```

Free, unlimited evaluation: the trial license runs for 30 minutes per
application start. You do not need a license key for it. ZIP packages, builds for LabVIEW,
Unity, and .NET Framework 3.5, and OPC Watch are available on the
[Downloads](https://www.traeger.de/en/docs/development/opcua/downloads) page.

## Get started

- [OPC UA basics](https://www.traeger.de/en/docs/development/opcua/opc-ua-basics): Nodes, NodeIds and namespaces, address space, views, node managers, and services.

- [Requirements](https://www.traeger.de/en/docs/development/opcua/requirements): Target frameworks, runtime environments, and platforms the SDK supports.

- [Getting started with the client](https://www.traeger.de/en/docs/development/opcua/client/getting-started): Connect to a server, read a value, and close the connection.

- [Getting started with the server](https://www.traeger.de/en/docs/development/opcua/server/getting-started): Create a server, start it, and shut it down again.

## Topics

- **Client development**
  - [Read and write values](https://www.traeger.de/en/docs/development/opcua/client/read-write-values)
  - [Browse nodes](https://www.traeger.de/en/docs/development/opcua/client/browse)
  - [Subscriptions](https://www.traeger.de/en/docs/development/opcua/client/subscriptions)
  - [Events](https://www.traeger.de/en/docs/development/opcua/client/events)
  - [Long-running clients](https://www.traeger.de/en/docs/development/opcua/client/long-running-clients)
  - [All client development topics](https://www.traeger.de/en/docs/development/opcua/client/)

- **Server development**
  - [Provide data from a device](https://www.traeger.de/en/docs/development/opcua/server/device-gateway)
  - [Manage nodes](https://www.traeger.de/en/docs/development/opcua/server/node-management)
  - [Read and write values](https://www.traeger.de/en/docs/development/opcua/server/read-write-values)
  - [Historical data](https://www.traeger.de/en/docs/development/opcua/server/historical-data)
  - [NodeSets](https://www.traeger.de/en/docs/development/opcua/server/nodesets)
  - [All server development topics](https://www.traeger.de/en/docs/development/opcua/server/)

- **Security**
  - [Understand certificates](https://www.traeger.de/en/docs/development/opcua/security/certificates)
  - [Users and roles](https://www.traeger.de/en/docs/development/opcua/security/users-roles)
  - [Secure clients](https://www.traeger.de/en/docs/development/opcua/security/client)
  - [Secure servers](https://www.traeger.de/en/docs/development/opcua/security/server)

- **Licensing**
  - [Licenses](https://www.traeger.de/en/docs/development/opcua/license)
  - [Set up the license](https://www.traeger.de/en/docs/development/opcua/license-setup)

- **Resources**
  - [Downloads](https://www.traeger.de/en/docs/development/opcua/downloads)
  - [Sample applications](https://www.traeger.de/en/docs/development/opcua/samples)
  - [OPC Watch](https://releases.traeger.de/artifacts/OpcWatch/windows/any/latest)
  - [llms.txt](https://www.traeger.de/en/docs/llms.txt): this documentation for AI assistants

- **Help and reference**
  - [FAQ](https://www.traeger.de/en/docs/development/opcua/faqs)
  - [SDK internals](https://www.traeger.de/en/docs/development/opcua/internals)
  - [Tracing](https://www.traeger.de/en/docs/development/opcua/tracing)
  - [Version history](https://www.traeger.de/en/docs/development/opcua/version-history)
  - [Upgrade to a new version](https://www.traeger.de/en/docs/development/opcua/upgrade)

- [API reference](https://www.traeger.de/en/docs/development/opcua/api/v2.59/): all classes, methods and properties of the SDK, by namespace and by topic.

## Get help

The [FAQ](https://www.traeger.de/en/docs/development/opcua/faqs) page already answers many questions. If you do not find an
answer there, our support team helps you, even during the evaluation:

- E-mail: [support@traeger.de](mailto:support@traeger.de), Reply usually within one business day
- Phone: [+49 961 48 23 0-0](tel:+49961482300), Mon. to Thu. 8:00⁠–⁠17:00 CET, Fri. 8:00⁠–⁠14:00 CET
- Request form: [Send a request](https://www.traeger.de/en/contact?intent=support), We get back to you within 24 hours

**What helps us respond faster:**

- Identification: SDK variant, version, serial number¹
- Problem: description of the behavior, steps to reproduce, logs or screenshots

¹ Not required during the evaluation.