A lightweight wrapper for OPCDAAuto.dll that brings classic OPC DA connectivity to Node-RED. A C# background worker handles COM operations through a persistent asynchronous stdin/stdout

Prerequisites

OPC DA is a legacy Windows-only technology built on COM/DCOM architecture. To use these nodes, you must satisfy the following requirements:

Operating System: Windows (Windows 7/10/11, Windows Server, etc.)

register OPCDAAuto.dll(If a notification hasn't been set up, a prompt to register will appear upon the first login.)

It is recommended to run Node-RED on the same machine as the OPC DA server.

Main Features

• Persistent Connection Management: Spawns a single, shared background C# instance per OPC server connection to keep resource usage minimal.
• Dynamic Server Discovery: Automatically queries and displays all installed local or remote (via DCOM) OPC DA servers in a dropdown selection.
• Read Mode: Performs fast synchronous batch tag reads, returning values, quality codes, and ISO timestamps.
• Write Mode: Support writing typed values (Int16, Int32, Float, Double, Boolean, String, etc.) to OPC DA variables.
• Browse Mode: Features a tree explorer UI in the editor configuration modal to browse tags and folders dynamically.
• Browse Recursive Mode: Automatically walks folder hierarchies recursively, gathers all child leaves, and returns a fully populated nested tree containing all read tag values.
• Subscription Mode: Subscribes to real-time value changes on selected groups of tags, emitting change events immediately.
• Configurable Command Timeouts: Fully parameterizable command execution timeout to avoid flow blocks during slow DCOM network reads.

Node Configurations

1. Connection Configuration (opcda-client-config)

• Node Name (Optional): Specifies the computer name or IP address of a remote DCOM host. If left empty, discovery and connection are performed on the local machine.
• Select Server: A dropdown list with a refresh button to scan and choose registered OPC DA servers.
• Server ProgID: The exact programmatic identifier of the OPC server (e.g. Matrikon.OPC.Simulation.1, Kepware.KEPServerEX.V6).
• Command Timeout (ms): Adjustable timeout (in milliseconds) for execution commands.

2. Client Node (opcda-client)

• Mode: Choose between Read, Write, Browse, Browse Recursive, and Subscription.
• Browse Tree: Click to open a visual explorer modal supporting folder expansion, Ctrl + click multi-selections, and instant itemID copying.
• Update Rate (ms): Available in subscription mode to control polling check frequency.

Client config

Client Editor

Support the Project

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@vitormnm