Demo simplified and slightly expanded

README.md

@@ -1,21 +1,34 @@
-socket-ntp
+socket-ntp-krcmod
 ==========
 
-NTP Sync using Socket.io. Allows you to sync clients against a server by calculating the time offset.
+NTP Sync using Socket.io.  Provides current time on webserver as well as the client offset from the webserver.
+
+My take on Calvin French-Owen (calvinfo)'s concise socket-ntp.  Can be used as a drop-in replacement.  
+
+I used the basic framework and made it needlessly more complicated :)
+
+* Lower ping times are valued over higher since there's less chance of error in the NTP calculation
+* Interrogates strong for 20 seconds, then throttles back to preserve resources
+* added ntp.serverTime() for us lazybones
+* Demo: Streamlined the express code. Added a primitive scheduler for synchronizing events across multiple nodes
+* Demo: Socket.io client switched to the one automatically served by socket.io
+* Demo: We didn't really need jQuery in there
+
 
 ## Installation
 
 ```
-npm install socket-ntp
+npm install socket-ntp-krcmod
 ```
 Requires access to [socket.io](http://socket.io/) connections on both the client and the server.
 
+
 ## Client usage
 
 On the client, include:
 
 ```html
-<script src="/javascripts/libs/socket.io.min.js"></script>
+<script src="/socket.io/socket.io.js"></script>
 <script src="/client/ntp.js"></script>
 ```
 
@@ -24,15 +37,16 @@ On the client, include:
   var socket = io.connect();
   ntp.init(socket);  
 
-  var offset = ntp.offset(); // time offset from the server in ms 
+  var offset = ntp.offset(); // time offset from the server in ms
+  var servertime = ntp.serverTime(); //what time is it on the server (equivalent to Date.now())
 ```
 
 ## Server usage
 
 From anywhere that you have access to a socket.io instance.
 
 ```javascript
-var ntp = require('socket-ntp');
+var ntp = require('socket-ntp-krcmod');
 
 io.sockets.on('connection', function (socket) {
   ntp.sync(socket);
@@ -70,4 +84,4 @@ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

client/ntp.js

@@ -1,50 +1,75 @@
 (function (root) {
 
-  var ntp  = {}
-    , offsets = []
-    , socket;
+	var ntp  = {}
+	, offsets = []
+	, socket;
 
-  ntp.init = function (sock, options) {
-    options = options || {};
+	ntp.init = function (sock) {
+		socket = sock;
+		socket.on('ntp:server_sync', onSync);
+		sync();
+	};
 
-    socket = sock;
-    socket.on('ntp:server_sync', onSync);
-    setInterval(sync, options.interval || 1000);
-  };
+	var onSync = function (data) {
 
-  var onSync = function (data) {
+		var diff = Date.now() - data.t1 - ((Date.now() - data.t0)/2);
+		var ping = Date.now() - data.t0;
+		offsets.unshift([ping,diff]);
 
-    var diff = Date.now() - data.t1 + ((Date.now() - data.t0)/2);
+		if (offsets.length > 20){
+			offsets.pop();
+		}
 
-    offsets.unshift(diff);
+	};
 
-    if (offsets.length > 10)
-      offsets.pop();
-  };
+	ntp.offset = function () {
+		var sum = 0;
+		var offsetsSorted = offsets.slice(0); //make a copy of the offsets array for sorting.  Keep the original so the times keep cycling.
+		offsetsSorted.sort(sort2dArray);
 
+		if (offsetsSorted.length >4){ //get rid of everything except the 4 lowest ping times.
+			for (var i = 0; i < offsets.length-3; i++) {
+				offsetsSorted.pop();
+			}
+		}
+		for (var i = 0; i < offsetsSorted.length; i++) { //add up and average the 4 offset times associated with the lowest ping times
+			sum += offsetsSorted[i][1];
+		}
 
-  ntp.offset = function () {
-    var sum = 0;
-    for (var i = 0; i < offsets.length; i++)
-      sum += offsets[i];
+		sum /= offsetsSorted.length;
+		return sum;
+	};
 
-    sum /= offsets.length;
+	ntp.serverTime = function () {
+		return Math.round(Date.now() -ntp.offset());
+	};
 
-    return sum;
-  };
+	var sync = function () {
+		socket.emit('ntp:client_sync', { t0 : Date.now() });
+		//console.log(ntp.offset() + " is the current offset");
+		if (offsets.length <19){ //every second for the first 20, every 5 after.  To reduce network traffic.
+			setTimeout(function(){sync();}, 1000)
+		}	else{
+			setTimeout(function(){sync();}, 5000)
+		}
+	};
 
+	var sort2dArray = function (a, b) { //for sorting the 2d array by ping time
+		if (a[0] === b[0]) {
+			return 0;
+		}
+		else {
+			return (a[0] < b[0]) ? -1 : 1;
+		}
+	}
 
-  var sync = function () {
-    socket.emit('ntp:client_sync', { t0 : Date.now() });
-  };
-
-  // AMD/requirejs
-  if (typeof define === 'function' && define.amd) {
-    define('ntp', [], function () {
-      return ntp;
-    });
-  } else {
-    root.ntp = ntp;
-  }
+	// AMD/requirejs
+	if (typeof define === 'function' && define.amd) {
+		define('ntp', [], function () {
+			return ntp;
+		});
+	} else {
+		root.ntp = ntp;
+	}
 
 })(window);

example/app.js

@@ -1,43 +1,20 @@
 
-var fs        = require('fs')
-  , path      = require('path')
-  , http      = require('http')
+var http      = require('http')
   , express   = require('express')
   , socketio  = require('socket.io')
   , ntp       = require('../');
 
-
 var app    = express()
   , server = http.createServer(app)
   , io     = socketio.listen(server);
+DEBUG=''; //turn off heartbeat messages, socket.io 1.10 and later
 
-
-app.get('/', function (req, res) {
-
-  var file = path.resolve(__dirname, './index.html');
-
-  fs.createReadStream(file).pipe(res);
-});
-
-
-app.get('/client/:filename', function (req, res, next) {
-
-  debugger;
-
-  var filename = req.param('filename')
-    , filepath = path.resolve(__dirname, '../client/', filename);
-
-  fs.exists(filepath, function (exists) {
-
-    if (exists)
-      fs.createReadStream(filepath).pipe(res);
-    else
-      res.send(404, 'Page not found!');
-  });
-});
-
+app.use(express.static(__dirname)); 
+app.use('/client', express.static('../client/')); 
 
 io.sockets.on('connection', ntp.sync);
 
+server.listen(80);
+
+console.log ("Starting application on *:80");
 
-server.listen(3000);

example/index.html

@@ -1,22 +1,25 @@
 <html>
   <head>
-    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
-    <script src="/client/socket.io.min.js"></script>
+    <script src="/socket.io/socket.io.js"></script>
     <script src="/client/ntp.js"></script>
-
+    
     <script>
-
-      var socket = io.connect();
-
-      ntp.init(socket);
-      setInterval(function () {
-        $('#offset').text(ntp.offset());
-      }, 1000);
+			var socket = io.connect();
+			ntp.init(socket);      
+
+        setInterval(function () {
+	      	setTimeout(function(){
+		        document.getElementById("offset").innerHTML=  "Server time: " + ntp.serverTime(); //what time the server thinks it is
+		        document.getElementById("offset").innerHTML+= "<p>Offset: " + ntp.offset();
+
+		      },( 1000-(Date.now() - ntp.offset())%1000));//update the display at our guess of where the server thinks a new second occurs
+        },1000);
+
     </script>
 
-
   </head>
   <body>
     <span id="offset"></span>
+
   </body>
 </html>

package.json

@@ -1,19 +1,26 @@
 {
-  "name": "socket-ntp",
-  "version": "0.1.0",
+  "name": "socket-ntp-krcmod",
+  "version": "0.2.0",
   "main": "lib/ntp",
-  "description": "NTP syncing algorithm between client and server using socket.io",
+  "description": "Enhanced NTP syncing algorithm between client and server using socket.io",
   "keywords": ["ntp", "socket", "socket.io"],
   "author": "Calvin French-Owen <[email protected]>",
+  "contributors": [{
+		"name": "Ross Brackett",
+		"email": "[email protected]"
+	}],
   "scripts": {
     "start": "node example/app.js"
   },
   "devDependencies": {
-    "express": "3.0.2",
+    "express": ">=3.0.2",
     "socket.io": "*"
   },
+  "homepage": "https://github.com/karaokeresearch/socket-ntp-krcmod",
+	"bugs": "https://github.com/karaokeresearch/socket-ntp-krcmod/pulls",
+	"license": "MIT",
   "repository": {
     "type": "git",
-    "url": "[email protected]:calvinfo/socket-ntp.git"
+    "url": "[email protected]:karaokeresearch/socket-ntp-krcmod.git"
   }
 }