async_server.js

/* eslint-disable no-console, no-unused-vars, spaced-comment */

// create an empty modbus client
//var ModbusRTU = require("modbus-serial");
var ModbusRTU = require("../index");
var vector = {
    getInputRegister: function(addr, unitID) {
        // Synchronous handling
        return addr;
    },
    getHoldingRegister: function(addr, unitID, callback) {
        // Asynchronous handling (with callback)
        setTimeout(function() {
            // callback = function(err, value)
            callback(null, addr + 8000);
        }, 10);
    },
    getCoil: function(addr, unitID) {
        // Asynchronous handling (with Promises, async/await supported)
        return new Promise(function(resolve) {
            setTimeout(function() {
                resolve(addr % 2 === 0);
            }, 10);
        });
    },
    getDiscreteInput: function(addr, unitID) {
        // Asynchronous handling (with Promises, async/await supported)
        return new Promise(function(resolve) {
            setTimeout(function() {
                resolve(addr % 2 === 0);
            }, 10);
        });
    },
    setRegister: function(addr, value, unitID) {
        // Asynchronous handling supported also here
        console.log("set register", addr, value, unitID);
        return;
    },
    setCoil: function(addr, value, unitID) {
        // Asynchronous handling supported also here
        console.log("set coil", addr, value, unitID);
        return;
    },
    readDeviceIdentification: function(unitID) {
        return new Promise(function(resolve) {
            setTimeout(function() {
                resolve({
                    0x00: "MyVendorName",
                    0x01: "MyProductCode",
                    0x02: "MyMajorMinorRevision",
                    0x05: "MyModelName",
                    0x97: "MyExtendedObject1",
                    0xAB: "MyExtendedObject2"
                });
            }, 10);
        });
    }
};

// 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);
});