node-red-tienho-modbus-tcp-high-speed

A high-speed, robust realtime Modbus TCP/IP reader node for Node-RED featuring an integrated Connection Pool and Batch Processing support.

This node acts as a Modbus TCP Master (Client) to read coils, inputs, and registers. It is optimized for industrial automation where high-frequency polling and multi-device connection management are critical.

Key Features in v2.1.2

• 🚀 High-Speed Connection Pool: TCP connections are cached and reused by ip:port. Checks raw socket status (destroyed, writable) before reuse. Sockets automatically close after a 10-second idle timeout to prevent PLC connection overload.
• ⚡ Concurrency & Intelligent Queueing: Requests to different IP addresses run in parallel, while requests to the same IP:Port are executed sequentially to prevent network race conditions or connection resets on PLCs/gateways.
• 📦 Batch Processing (Array Input): Pass an array of multiple request configurations in msg.payload.
• 🛡️ Fast Error Propagation: If a connection to a specific IP:Port fails, the node automatically propagates the error to all subsequent queued requests targeting the same IP:Port in the batch without wasting time reconnecting.
• 🎯 Standardized Output Format: Both single and batch requests return detailed objects containing connection metadata, status (success or error), raw response buffers, errors, and response duration times in msg.payload.
• 🛡️ Robust Error Handling: Connection failures or device exceptions do not halt your flow. The error state is safely encapsulated in the output payload, and standard Node-RED Catch Nodes are supported.

Installation

Run the following command in your Node-RED user directory (usually ~/.node-red):

npm install node-red-tienho-modbus-tcp-high-speed

Input Message Structure

You can configure the connection statically in the Node UI or pass it dynamically in msg.payload.

1. Single Request Format (Object)

Pass a single object inside msg.payload:

{
    "payload": {
        "functioncode": 3,
        "address": 1000,
        "quantity": 10,
        "unitid": 1,
        "modbus_ip": "192.168.1.10",    // Optional (falls back to UI config if omitted)
        "modbus_port": 502              // Optional (falls back to UI config if omitted)
    }
}

2. Batch Request Format (Array)

Pass an array of objects inside msg.payload to read from different servers/registers concurrently:

{
    "payload": [
        {
            "modbus_ip": "192.168.1.10",
            "modbus_port": 502,
            "functioncode": 3,
            "address": 100,
            "quantity": 2,
            "unitid": 1
        },
        {
            "modbus_ip": "192.168.1.20",
            "modbus_port": 502,
            "functioncode": 3,
            "address": 200,
            "quantity": 5,
            "unitid": 1
        }
    ]
}

Modbus Function Codes Supported

This node supports both Read and Write operations:

Read Operations

• 1: Read Coils (FC 01) — Requires quantity
• 2: Read Discrete Inputs (FC 02) — Requires quantity
• 3: Read Holding Registers (FC 03) — Requires quantity
• 4: Read Input Registers (FC 04) — Requires quantity

Write Operations (with Smart Data Parsing)

• 5: Write Single Coil (FC 05) — Requires value (accepts boolean true/false or 1/0)
• 6: Write Single Register (FC 06) — Requires value (accepts a number e.g. 123, automatically converted to 2-byte Buffer)
• 15: Write Multiple Coils (FC 15) — Requires values (accepts array e.g. [true, false, true])
• 16: Write Multiple Registers (FC 16) — Requires values (accepts array of numbers e.g. [100, 200], automatically converted to Buffer)

Output Message Structure

The results are always assigned directly to msg.payload with a comprehensive output schema.

1. Successful Query Result Example

{
    "payload": {
        "ip": "192.168.1.10",
        "port": 502,
        "address": 1000,
        "quantity": 10,
        "unitid": 1,
        "functioncode": 3,
        "status": "success",
        "buffer": [25, 218, 80, 100, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        "error": null,
        "durationMs": 15
    }
}

2. Failed Query Result Example

{
    "payload": {
        "ip": "192.168.1.33",
        "port": 502,
        "address": 0,
        "quantity": 10,
        "unitid": 1,
        "functioncode": 3,
        "status": "error",
        "buffer": null,
        "error": "Connection error: Connection refused"
    }
}

Note: For backward compatibility with v1.x, single requests will also populate msg.responseBuffer = { buffer: rawBuffer }, msg.ip, and msg.port on successful reads.

License

This project is licensed under the MIT License.