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PicoOPC is a smallest imaginable OPC Unified Architecture (OPC UA) client library. It works with any .NET 6+ conformant runtime. PicoOPC does not depend on any OPC UA stack. With PicoOPC, you can create and close sessions (opc.tcp), and perform reads and writes, synchronously or asynchronously. There is no support for security, browsing or subscriptions.

Use QuickOPC instead if you need an advanced, high-level OPC client toolkit.

PicoOPC is a commercially licensed product. Without a license key, it runs in a trial mode. The trial provides valid data to a client application for 30 minutes; after that period, the component (your app) needs to be re-started, and so on. For details, see the documentation.

PicoOPC requires a .NET runtime compatible with .NET 6+ 2.0.

Note: OPC Foundation has not published a profile for such small a client, and PicoOPC therefore cannot be officially claimed to comply with the OPC UA specifications, although in a technical sense, PicoOPC is highly interoperable.

PicoOPC for .NET is distributed as NuGet package "OpcLabs.PicoOPC", and is available from the public NuGet repository .

How to start

If you want to see some result quickly, reference the OpcLabs.PicoOPC package from your project, and paste in the example code further below. If you do not mind studying a bit, here is the documentation.


  • AttributeId: Identifiers assigned to attributes.
  • BuiltInType: Enumeration of built-in types.
  • Client: A minimalistic OPC UA client object.
  • DataValue: The value and associated information.
  • NodeId: Unambiguously identifies a node.
  • NodeIdType: Type of the node ID identifier.
  • ReadValueId: Identifier for an item to read.
  • Variant: A union of all built-in data types.
  • WriteValue: Describes a node, and its attribute and value.

Client object methods

  • Connect/ConnectAsync: Connects to the server.
  • Disconnect/DisconnectAsync: Disconnects from the server.
  • Read/ReadAsync: Reads one or more attributes of one or mode nodes.
  • Write/WriteAsync: Writes values to one or more attributes of one or more nodes.

Example code

using OpcLabs.PicoOpc.UA;

var client = new Client();
client.Connect(new Uri("opc.tcp://"));

// Read a node, then write 123 to it.
var nodeId = new NodeId(10221, namespaceIndex: 2);
DataValue dataValue = client.Read(TimeSpan.Zero, new [] {new ReadValueId(nodeId)})[0];

UInt32 statusCode = client.Write(new [] {new WriteValue(nodeId,
    new DataValue(new Variant(BuiltInType.Int32, 123)))})[0];



Footnote & required disclosure: PicoOPC is a software development kit (SDK) for development of OPC clients. Installing PicoOPC does not change system settings.