melsec-connect

A modern Node.js library for communicating with Mitsubishi MELSEC PLCs using MC Protocol. This library provides a robust, promise-based API with automatic connection management and comprehensive error handling.

Features

• 🚀 Promise-based modern API
• 🔄 Automatic connection management and recovery
• 🛡️ Comprehensive error handling and logging
• 🔌 Support for multiple simultaneous connections
• 📊 Detailed operation results with timestamps and quality indicators
• 🔧 Configurable timeouts and retry mechanisms

Installation

npm install melsec-connect

Quick Start

const { PLCClient } = require("melsec-connect");

// Configure your PLC connection
const config = {
  host: "192.168.1.10",
  port: 1281,
  protocol: "TCP",
  ascii: false,
  frame: "3E",
  plcType: "Q",
  timeout: 30000,
  retryInterval: 2000,
  maxRetries: 3,
};

async function example() {
  const plc = new PLCClient(config);

  try {
    // Read from PLC
    const readResult = await plc.read([{ name: "D100", count: 1 }]);
    console.log("Read result:", readResult);

    // Write to PLC
    const writeResult = await plc.write([{ name: "D200", value: 100 }]);
    console.log("Write result:", writeResult);
  } finally {
    await plc.disconnect();
  }
}

API Reference

PLCClient

Main class for PLC communication.

Constructor

const plc = new PLCClient(config);

Methods

• read(tags): Read values from PLC
• write(tags): Write values to PLC
• connect(): Explicitly connect to PLC
• disconnect(): Close the connection

Configuration Options

{
    host: string,          // PLC IP address
    port: number,          // PLC port number
    protocol: 'TCP',       // Protocol (TCP/UDP)
    ascii: boolean,        // Use ASCII mode
    frame: string,         // Frame type (1E/3E/4E)
    plcType: string,       // PLC type (Q/L/R)
    timeout: number,       // Operation timeout (ms)
    retryInterval: number, // Retry interval (ms)
    maxRetries: number,    // Maximum retry attempts
    logLevel: string      // Log level (DEBUG/INFO/WARN/ERROR)
}

Error Handling

The library provides detailed error information:

try {
    await plc.read([...]);
} catch (error) {
    console.error('PLC error:', error.message);
}

Examples

See the examples directory for more usage examples:

• Basic read/write operations
• Error handling
• Connection management
• Multiple PLC communication

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License - feel free to use this in your projects.

Support

If you encounter any issues or have questions, please file an issue on the GitHub repository.

Credits

This project was inspired by and builds upon the work of:

• mcprotocol
• node-red-contrib-mcprotocol