app.js

var http = require('http');
var fs = require('fs');
var index = fs.readFileSync('index.html');
var SerialPort = require('serialport');
const parsers = SerialPort.parsers;

const parser = new parsers.Readline({
    delimiter: '\r\n'
});

var port = new SerialPort('/dev/cu.usbserial-A50285BI', {
    baudRate: 9600,
    dataBits: 8,
    parity: 'none',
    stopBits: 1,
    flowControl: false
});

port.pipe(parser);

var app = http.createServer(function (req, res) {
    res.writeHead(200, { 'Content-Type': 'text/html' });
    res.end(index);
});

var io = require('socket.io').listen(app);

io.on('connection', function (socket) {

    socket.on('smarties', function (data) {

        console.log(data);
        port.write(data.status);

    });

});

app.listen(3000);