// create an empty modbus client
var ModbusRTU = require("modbus-serial");
var client = new ModbusRTU();

// open connection to a serial port
client.connectRTU("/dev/ttyUSB0", { baudrate: 9600 }, write);

function write() {
    client.setID(1);

    // write the values 0, 0xffff to registers starting at address 5
    // on device number 1.
    client.writeRegisters(5, [0 , 0xffff])
        .then(read);
}

function read() {
    // read the 2 registers starting at address 5
    // on device number 1.
    client.readHoldingRegisters(5, 2)
        .then(console.log);
}

// create an empty modbus client
var ModbusRTU = require("modbus-serial");
var client = new ModbusRTU();

// open connection to a serial port
client.connectRTUBuffered("/dev/ttyUSB0", { baudrate: 9600 });
client.setID(1);

// read the values of 10 registers starting at address 0
// on device number 1. and log the values to the console.
setInterval(function() {
    client.readHoldingRegisters(0, 10, function(err, data) {
        console.log(data.data);
    });
}, 1000);

// create an empty modbus client
var ModbusRTU = require("modbus-serial");
var client = new ModbusRTU();

// open connection to a tcp line
client.connectTCP("127.0.0.1", { port: 8502 });
client.setID(1);

// read the values of 10 registers starting at address 0
// on device number 1. and log the values to the console.
setInterval(function() {
    client.readHoldingRegisters(0, 10, function(err, data) {
        console.log(data.data);
    });
}, 1000);

// create an empty modbus client
var ModbusRTU = require("modbus-serial");
var vector = {
    getInputRegister: function(addr, unitID) { return addr; },
    getHoldingRegister: function(addr, unitID) { return addr + 8000; },
    getCoil: function(addr, unitID) { return (addr % 2) === 0; },
    setRegister: function(addr, value, unitID) { console.log("set register", addr, value, unitID); return; },
    setCoil: function(addr, value, unitID) { console.log("set coil", addr, value, unitID); return; }
};

// set the server to answer for modbus requests
console.log("ModbusTCP listening on modbus://0.0.0.0:8502");
var serverTCP = new ModbusRTU.ServerTCP(vector, { host: "0.0.0.0", port: 8502, debug: true, unitID: 1 });

serverTCP.on("socketError", function(err){
    // Handle socket error if needed, can be ignored
    console.error(err);
});