node server for talking to XY Plotter

serv.js

var express = require('express')
var bodyparser = require('body-parser')
var sp = require('serialport')
var SerialPort = sp.SerialPort
var app = express()
app.all('/', function(req, res, next) {
	 res.header("Access-Control-Allow-Origin", "*");
	 res.header("Access-Control-Allow-Methods", "GET,PUT,POST,DELETE,OPTIONS");
	 res.header("Access-Control-Allow-Headers", "Content-Type, Accept, X-Requested-With, Session");
	 next();
});

var curx = 0;
var cury = 0;
var curs = 100;
//parse application/json
app.use(bodyparser.json());


// Expects requests of the form {x : <float in range [0, 1]> y : <float in range [0, 1]>]}
app.use(function (req, res, next) {
	console.log(req.body);
  // For CORS, you might need to remove this
  if (req.method === "OPTIONS") {
	            return res.status(200).end();
  }
  // Flip coords
	var x = 1 - parseFloat(req.body.x);
	var y = 1 - parseFloat(req.body.y);
	if(x == NaN) return;
  
  // The actual GCODE commands
  // Other GCODE commands may also work
  // Also, look at the mDraw python documentation
	console.log("G1 X" + (x * 380) + ".00 Y" + (y * 310) + ".00\n");
	port.write("G1 X" + (x * 380) +".00 Y" + (y * 310) + ".00\n",
		   function(err, written) {
			curs = curs += 5;
			console.log("M2 U" + curs + " D" + curs + "\n")
		   	port.write("M2 U" + curs + " D" + curs + "\n", function(err, written) {
				port.write("G1 X0.00 Y0.00\n", function() {port.write('M10\n')});
			})
		   });
	next(); // Continuation 
})

sp.list((err, ports) => {for (var port of ports) { console.log(port) } } )
var port = new SerialPort('/dev/cu.wchusbserial1410', { 
	parser : sp.parsers.readline('\n'),
	baudrate: 115200})
port.on('open', function () { port.write('M11\n', function() {port.write('M11\n')}) })
port.on('data', function (data) {
	  console.log('Data: ' + data);
});

app.listen(8999);