server.js

var fs = require('fs'),
http = require('http'),
socketio = require('socket.io'),
url = require("url"), 
SerialPort = require("serialport").SerialPort,
connection = require('./db');

var reDensity = /(\d+)\s+$/;

var socketServer;
var serialPort;
var portName = '/dev/tty.wch ch341 USB=>RS232 1410'; //change this to your Arduino port
var sendData = "";

var httpServer = http.createServer(function (request, response) {
	connection.query('SELECT * FROM tblSensorData', function (err, rows, fields) {
		response.writeHead(501, { 'Content-Type': 'application/json' });
    	response.end(JSON.stringify(rows));
	});
}).listen(9090);

// handle contains locations to browse to (vote and poll); pathnames.
function startServer(route,handle,debug)
{
	// on request event
	function onRequest(request, response) {
	  // parse the requested url into pathname. pathname will be compared
	  // in route.js to handle (var content), if it matches the a page will 
	  // come up. Otherwise a 404 will be given. 
	  var pathname = url.parse(request.url).pathname; 
	  console.log("Request for " + pathname + " received");
	  var content = route(handle,pathname,response,request,debug);
	}
	
	var httpServer = http.createServer(onRequest).listen(1337, function(){
		console.log("Listening at: http://localhost:1337");
		console.log("Server is up");
	}); 
	serialListener(debug);
	initSocketIO(httpServer,debug);
}

function initSocketIO(httpServer,debug)
{
	socketServer = socketio.listen(httpServer);
	if(debug == false){
		socketServer.set('log level', 1); // socket IO debug off
	}
	socketServer.on('connection', function (socket) {
		console.log("user connected");
		socket.emit('onconnection', {pollOneValue:sendData});
		socketServer.on('update', function(data) {
			socket.emit('updateData',{pollOneValue:data});
		});
		socket.on('buttonval', function(data) {
			serialPort.write(data + 'E');
		});
		socket.on('sliderval', function(data) {
			serialPort.write(data + 'P');
		});
    });
}

// Listen to serial port
function serialListener(debug) {
    serialPort = new SerialPort(portName, {
        baudrate: 9600,
        // defaults for Arduino serial communication
         dataBits: 8,
         parity: 'none',
         stopBits: 1,
         flowControl: false
    });
 
    serialPort.on("open", function () {
		console.log('open serial communication');

    	// Listens to incoming data
        serialPort.on('data', function(data) {
			data = data.toString();
    		console.log(data);

   			var density = data.match(reDensity)[1]; 
			
			if (density) {
           		sendData = data.substring(data.indexOf('B') + 1, data .indexOf('E'));

				// send the incoming data to browser with websockets.
				socketServer.emit('update', sendData);

				connection.query('INSERT INTO tblSensorData SET ?', {DATE: new Date(), CO2: density}, function (err) {
					if (err) console.error('Error writing to db:', err.toString);
				});
      		}  else {
      			console.error('No match for received Arduino data!');
      		}
    	});  
	});
}

exports.start = startServer;