server.js

var express = require('express');
var sys = require("sys");
var util = require('util');
var socketio = require("socket.io");
var dgram = require('dgram');

var lightswitch_socket = dgram.createSocket("udp4");
var lightswitch_value = 0;
var last_lightswitch_value = 0;

app = express.createServer();

app.listen(8080);

app.configure(function(){
    app.use(express.methodOverride());
    app.use(express.bodyParser());
    app.use(app.router);
    app.use(express.static(__dirname + '/public'));
    app.use(express.errorHandler({ dumpExceptions: true, showStack: true }));
});

var io = socketio.listen(app);

io.sockets.on('connection', function(client) {

  client.on('slider', function(message) {

    var value = (Math.floor(parseInt(message.value)*2.55));
    var value_in_hex = value.toString(16);

    if (value <= 16) value_in_hex = "0" + value_in_hex;

    var buffer = new Buffer("0000000000" + value_in_hex + "0000\x0d\x0a");

    lightswitch_socket.send(buffer, 0, 18, 9802, '192.168.0.1');

  });
});