Modbus Stream

This is a NodeJS module to help you process modbus data. It uses pdu to build the core PDU and then uses transports to extend the rest.

Features

• Support almost every standard function code
• Support standard exceptions
• Support transports
  • TCP
  • RTU
  • ASCII
• Support drivers
  • TCP
  • UDP
  • Serial (RS232, RS485)

Example

This is my current test.js file. It creates a client and a server network socket and the server requests coils as soon as the client connects.

var modbus = require("modbus-stream");

modbus.tcp.server({ debug: "server" }, (connection) => {
    connection.readCoils({ from: 3, to: 7 }, (err, info) => {
        console.log("response", info.response.data);
    });
}).listen(12345, () => {
    modbus.tcp.connect(12345, { debug: "client" }, (err, connection) => {
        connection.on("read-coils", (package, reply) => {
            reply(null, [ 1, 0, 1, 0, 1, 1, 0, 1 ]);
        });
    });
});

Usage

Connection

To connect to a modbus device over TCP, use:

var modbus = require("modbus-stream");

modbus.tcp.connect(502, "134.2.56.231", { debug: "automaton-2454" }, (err, connection) => {
    // do something with connection
});

To listen for connections over TCP, use:

var modbus = require("modbus-stream");

modbus.tcp.server({ debug: "server" }, (connection) => {
    // do something with connection
}).listen(502, () => {
    // ready
});

To connecto to a modbus device over a serial port, use:

var modbus = require("modbus-stream");

modbus.serial.connect("/dev/ttyS123", { debug: "automaton-123" }, (err, connection) => {
    // do something with connection
});

Requests

After having a connection, you can send requests and listen for responses.

modbus.serial.connect("/dev/ttyS123", { debug: "automaton-123" }, (err, connection) => {
    if (err) throw err;

    connection.readCoils({ address: 52, quantity: 8 }, (err, res) => {
        if (err) throw err;

        console.log(res); // response
    })
});

Every method accepts and object options which have defaults parameters (like address = 0) and a callback, in case you want to see the response from the remote device. Here is a list of supported function codes and the corresponding methods:

Base Reads

• readCoils (address = 0, quantity = 1)
• readDiscreteInputs (address = 0, quantity = 1)
• readHoldingRegisters (address = 0, quantity = 1)
• readInputRegisters (address = 0, quantity = 1)

Base Writes

• writeSingleCoil (address = 0, value = 0)
• writeSingleRegister (address = 0, value = <Buffer 0x00 0x00>)
• writeMultipleCoils (address = 0, values = [])
• writeMultipleRegisters (address = 0, values = [ <Buffer 0x00 0x00> ])

File Records

• readFileRecord (requests = [])
• writeFileRecord (requests = [])

FIFO

• readFifoQueue (address = 0)

Advanced

• maskWriteRegister (address = 0, andmask = 0xFFFF, ormask = 0x0000)
• readWriteMultipleRegisters (read_address = 0, read_quantity = 1, write_address = 0, values = [ <Buffer 0x00 0x00> ])
• readDeviceIdentification (type = "BasicDeviceIdentification", id = "ProductName")
• readExceptionStatus ()
• getCommEventCounter ()
• getCommEventLog ()

Responses

To respond to remote requests, listen for events.

modbus.serial.connect("/dev/ttyS123", {
    // except "debug", everything else is the default for serial
    baudRate : 9600,
    dataBits : 8,
    stopBits : 1,
    parity   : "none",
    debug    : "automaton-123"
}, (err, connection) => {
    if (err) throw err;

    connection.events.on("read-coils", (req, reply) => {
        console.log(req); // request

        // ...
        return reply(null, [ data ]);
    })
});