introduce udp poller

lib/pollers/udp.js

@@ -0,0 +1,85 @@
+/**
+ * Module dependencies.
+ */
+
+var util = require('util'),
+    dgram = require('dgram'),
+    BasePoller = require('./base');
+/**
+ * starting UDP server
+ */
+var udpServer = dgram.createSocket('udp4');
+/**
+ * binding required for getting responses
+ * */
+udpServer.bind();
+udpServer.on('error', function () {});
+/**
+ * Poller constructor
+ *
+ * @param {Mixed} Poller Target (e.g. URL)
+ * @param {Number} Poller timeout in milliseconds. Without response before this duration, the poller stops and executes the error callback.
+ * @param {Function} Error/success callback
+ * @api   public
+ */
+function UdpPoller(target, timeout, callback) {
+  UdpPoller.super_.call(this, target, timeout, callback);
+}
+
+util.inherits(UdpPoller, BasePoller);
+
+UdpPoller.prototype.initialize = function() {
+  this.udpServer = udpServer;
+  var reg = new RegExp('udp:\/\/(.*):(\\d{1,5})');
+  if(!reg.test(this.target)) {
+   console.log(this.target + ' does not seems to be valid udp url');
+  }
+  var host = reg.exec(this.target);
+  this.target = {
+    'address': host[1],
+    'port': host[2]
+  };
+}
+
+/**
+ * Launch the actual polling
+ *
+ * @api   public
+ */
+UdpPoller.prototype.poll = function() {
+  UdpPoller.super_.prototype.poll.call(this);
+  var ping = new Buffer(JSON.stringify({'command': 'ping'}));
+  this.udpServer.send(ping, 0, ping.length, this.target.port, this.target.address);
+  this.udpServer.on("message", this.onResponseCallback.bind(this));
+}
+
+/**
+ * Response callback
+ * @api   private
+ */
+UdpPoller.prototype.onResponseCallback = function(message, sender) {
+  this.debug(this.getTime() + 'ms - got answer from ' + sender.address + ':' + sender.port);
+  var cmd;
+  try {
+    cmd = JSON.parse(message);
+  } catch (e) {
+    return this.onErrorCallback({ name: "Unparsable answer", message: "server return answer " + message.toString()});
+  }
+  if (cmd.command === 'pong') {
+    this.timer.stop();
+    this.debug(this.getTime() + 'ms - Got response');
+    this.callback(null, this.getTime(), cmd);
+  }
+}
+
+/**
+ * Timeout callback
+ *
+ * @api   private
+ */
+UdpPoller.prototype.timeoutReached = function() {
+  UdpPoller.super_.prototype.timeoutReached.call(this);
+  this.udpServer.removeAllListeners();
+}
+
+module.exports = UdpPoller;