Resolve #61

Author: decebals

_posts/2015-03-17-demo.md

@@ -3,7 +3,7 @@ layout: page
 title: "Demo"
 category: doc
 date: 2015-03-17 17:42:47
-order: 200
+order: 210
 ---
 
 The demo applications are in [pippo-demo](https://github.com/decebals/pippo-demo) repository: 

_posts/2016-08-08-deployment.md

@@ -3,7 +3,7 @@ layout: page
 title: "Deployment"
 category: doc
 date: 2016-08-08 09:46:53
-order: 201
+order: 220
 ---
 
 #### Packaging

_posts/2017-07-18-hot-reloading.md

@@ -7,6 +7,7 @@ order: 199
 ---
 
 #### How to use
+
 This feature allows you to write code, save the code on disk and reload the web page from browser without restart the application (from IDE).
 
 ```java
@@ -41,6 +42,7 @@ You can supply the application class name using one of the below methods:
 - use `-Dpippo.applicationClassName` system property
 
 #### How works
+
 To implement hot reloading, Pippo introduces two new concepts (classes in package `ro.pippo.core.reload`):
 
 - `ReloadWatcher`

_posts/2017-07-20-websocket.md

@@ -0,0 +1,102 @@
+---
+layout: page
+title: "WebSocket"
+category: doc
+date: 2017-07-20 20:03:09
+order: 200
+---
+
+#### How to use
+
+Pippo allows you to use [WebSocket](https://en.wikipedia.org/wiki/WebSocket) in your application in an easy and uniform mode.
+You use the same interface for all major embedded web server supported by Pippo builtin (Jetty, Tomcat and Undertow).  
+ 
+The `Application` class contains a method with the signature:
+
+``` java
+public void addWebSocket(String path, WebSocketHandler webSocketHandler);
+```
+
+`WebSocketHandler` is an interface (functional) that contains one method 
+
+``` java
+void onMessage(WebSocketContext webSocketContext, String message);
+```
+
+and some default methods.
+
+To add an echo application based on websocket you should write something similar with:
+
+``` java
+// add web socket
+addWebSocket("/ws/echo", (webSocketContext, message) -> {
+    try {
+        webSocketContext.sendMessage(message);
+    } catch (IOException e) {
+        e.printStackTrace();
+    }
+});
+```
+
+If you need more control you can override other methods available in `WebSocketHandler`:
+
+``` java
+addWebSocket("/ws/echo", new WebSocketHandler() {
+
+    @Override
+    public void onMessage(WebSocketContext webSocketContext, String message) {
+        System.out.println("TestWebSocket.onMessage");
+        System.out.println("message = " + message);
+        try {
+            webSocketContext.sendMessage(message);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    @Override
+    public void onMessage(WebSocketContext webSocketContext, byte[] message) {
+        System.out.println("TestWebSocket.onMessage");
+    }
+
+    @Override
+    public void onOpen(WebSocketContext webSocketContext) {
+        System.out.println("TestWebSocket.onOpen");
+    }
+
+    @Override
+    public void onClose(WebSocketContext webSocketContext, int closeCode, String message) {
+        System.out.println("TestWebSocket.onClose");
+    }
+
+    @Override
+    public void onTimeout(WebSocketContext webSocketContext) {
+        System.out.println("TestWebSocket.onTimeout");
+    }
+
+    @Override
+    public void onError(WebSocketContext webSocketContext, Throwable t) {
+        System.out.println("TestWebSocket.onError");
+    }
+
+});
+```
+
+In above example, I used a standard `Route` to serve the `index.html` file that contains the script block with the websocket client side:
+
+``` java
+GET("/", routeContext -> {
+    try {
+        routeContext.send(IoUtils.toString(WebSocketApplication.class.getResourceAsStream("/index.html")));
+    } catch (IOException e) {
+        e.printStackTrace();
+    }
+});
+
+// OR
+
+DirectoryHandler directoryHandler = new DirectoryHandler("/", new File("src/main/resources"));
+GET(directoryHandler.getUriPattern(), directoryHandler);
+```
+
+**Note** A functional demo is available to [pippo-demo-websocket]({{ site.demourl }}/pippo-demo-websocket).