https://github.com/tootallnate/node-modbus-stack

A `StreamStack` implementation of the MODBUS protocol, for NodeJS.
https://github.com/tootallnate/node-modbus-stack

Last synced: 4 days ago
JSON representation

A `StreamStack` implementation of the MODBUS protocol, for NodeJS.

• Host: GitHub
• URL: https://github.com/tootallnate/node-modbus-stack
• Owner: TooTallNate
• License: mit
• Created: 2010-11-24T02:45:30.000Z (about 14 years ago)
• Default Branch: master
• Last Pushed: 2012-10-05T14:53:49.000Z (about 12 years ago)
• Last Synced: 2024-04-10T02:24:13.007Z (9 months ago)
• Language: JavaScript
• Homepage:
• Size: 177 KB
• Stars: 87
• Watchers: 9
• Forks: 37
• Open Issues: 5
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

README

        
node-modbus-stack

=================

### A [StreamStack][] implementation of the [MODBUS][Modbus] protocol for [Node][].

This module exposes two concrete `StreamStack` implementations:

`ModbusRequestStack` can be used as a MODBUS client (i.e. Master), and can write

MODBUS compliant requests and listen for the response.

`ModbusResponseStack` can be used to create a MODBUS server (i.e. Slave), by

listening for requests and providing a convenient API to respond with.

[MODBUS][ModbusWiki] is an open building automation protocol that is widely used

in various monitoring and controlling equipment. It's used with a variety of

different transports, including TCP.

Currently only communication through the TCP protocol is supported, however

RS-485 serial support should be possible with [node-serialport]. I haven't

had a chance to look into it yet.

A MODBUS Master (Client)

------------------------

You will need to know which _Function Code_ (defined in the MODBUS specification)

you are invoking on the remote MODBUS slave. In this example, we'll request to

read from the current values of the first 50 __Input Registers__ on the slave:

    // 'RIR' contains the "Function Code" that we are going to invoke on the remote device

    var RIR = require('modbus-stack').FUNCTION_CODES.READ_INPUT_REGISTERS;

    

    // IP and port of the MODBUS slave, default port is 502

    var client = require('modbus-stack/client').createClient(502, '10.0.1.50');

    

    // 'req' is an instance of the low-level `ModbusRequestStack` class

    var req = client.request(RIR, // Function Code: 4

                             0,    // Start at address 0

                             50);  // Read 50 contiguous registers from 0

    

    // 'response' is emitted after the entire contents of the response has been received.

    req.on('response', function(registers) {

      // An Array of length 50 filled with Numbers of the current registers.

      console.log(registers);

      client.end();

    });

A MODBUS Slave (Server)

-----------------------

`node-modbus-stack` makes it dead simple to create a compliant MODBUS Slave (or Server)

written in pure JavaScript. Here's an example of a server that would respond to the

request above:

    var FC = require('modbus-stack').FUNCTION_CODES;

    

    // 'handlers' is an Object with keys containing the "Function Codes" that your MODBUS

    // server will handle. Anything function code requested without a handler defined here

    // will have the Server transparently respond with Exception Code 1 ("Illegal Function")

    var handlers = {};

    

    // Define a handler for "Read Input Registers". We'll just respond with the register

    // number requested. In a real-world situation, you'd probably look up these values from

    // a database, etc.

    handlers[FC.READ_INPUT_REGISTERS] = function(request, response) {

      var start = request.startAddress;

      var length = request.quantity;

      

      var resp = new Array(length);

      for (var i=0; i