LED Webserver njs

var express = require('express');
app = express();
server = require('http').createServer(app);
io = require('socket.io').listen(server);

var SerialPort = require("serialport").SerialPort
var serialPort = new SerialPort("/dev/ttyACM0", { baudrate: 115200 });

server.listen(8080);
app.use(express.static('public'));

var brightness = 0;

io.sockets.on('connection', function (socket) {
    socket.on('led', function (data) {
        brightness = data.value;

        var buf = new Buffer(1);
        buf.writeUInt8(brightness, 0);
        serialPort.write(buf);

        io.sockets.emit('led', {value: brightness});
    });

    socket.emit('led', {value: brightness});
});

console.log("running");