Initial sketch of the GUI web-socket mechanics.

Change-Id: I5f481886fd45ce058be4aaf07fba466e702ae7ad
diff --git a/web/gui/src/main/webapp/WEB-INF/web.xml b/web/gui/src/main/webapp/WEB-INF/web.xml
index c5c6e28..ab7a550 100644
--- a/web/gui/src/main/webapp/WEB-INF/web.xml
+++ b/web/gui/src/main/webapp/WEB-INF/web.xml
@@ -39,4 +39,16 @@
         <url-pattern>/rs/*</url-pattern>
     </servlet-mapping>
 
+    <servlet>
+        <servlet-name>Web Socket Service</servlet-name>
+        <servlet-class>org.onlab.onos.gui.GuiWebSocketServlet</servlet-class>
+        <load-on-startup>2</load-on-startup>
+    </servlet>
+
+    <servlet-mapping>
+        <servlet-name>Web Socket Service</servlet-name>
+        <url-pattern>/ws/*</url-pattern>
+    </servlet-mapping>
+
+
 </web-app>
\ No newline at end of file
diff --git a/web/gui/src/main/webapp/topo2.js b/web/gui/src/main/webapp/topo2.js
index d345fda..e7444c9 100644
--- a/web/gui/src/main/webapp/topo2.js
+++ b/web/gui/src/main/webapp/topo2.js
@@ -40,6 +40,7 @@
             showBackground: true
         },
         backgroundUrl: 'img/us-map.png',
+        webSockUrl: 'ws/topology',
         data: {
             live: {
                 jsonUrl: 'rs/topology/graph',
@@ -130,6 +131,7 @@
             links: [],
             lookup: {}
         },
+        webSock,
         labelIdx = 0,
         selected = {},
         highlighted = null,
@@ -579,6 +581,52 @@
     }
 
     // ==============================
+    // Web-Socket for live data
+
+    function webSockUrl() {
+        return document.location.toString()
+            .replace(/\#.*/, '')
+            .replace('http://', 'ws://')
+            .replace('https://', 'wss://')
+            .replace('index2.html', config.webSockUrl);
+    }
+
+    webSock = {
+        ws : null,
+
+        connect : function() {
+            webSock.ws = new WebSocket(webSockUrl());
+
+            webSock.ws.onopen = function() {
+                webSock._send("Hi there!");
+            };
+
+            webSock.ws.onmessage = function(m) {
+                if (m.data) {
+                    console.log(m.data);
+                }
+            };
+
+            webSock.ws.onclose = function(m) {
+                webSock.ws = null;
+            };
+        },
+
+        send : function(text) {
+            if (text != null && text.length > 0) {
+                webSock._send(text);
+            }
+        },
+
+        _send : function(message) {
+            if (webSock.ws) {
+                webSock.ws.send(message);
+            }
+        }
+
+    };
+
+    // ==============================
     // View life-cycle callbacks
 
     function preload(view, ctx) {
@@ -656,6 +704,7 @@
             .on('tick', tick);
 
         network.drag = d3u.createDragBehavior(network.force, selectCb, atDragEnd);
+        webSock.connect();
     }
 
     function load(view, ctx) {
diff --git a/web/gui/src/main/webapp/ws.html b/web/gui/src/main/webapp/ws.html
new file mode 100644
index 0000000..cac99b2
--- /dev/null
+++ b/web/gui/src/main/webapp/ws.html
@@ -0,0 +1,54 @@
+<html>
+<head>
+    <title>Web Sockets Demo</title>
+
+    <script src="libs/jquery-2.1.1.min.js"></script>
+
+    <script type='text/javascript'>
+        if (!window.WebSocket)
+            alert("WebSocket not supported by this browser");
+
+        var server = {
+            connect : function() {
+                var location = document.location.toString().replace('http://',
+                        'ws://').replace('https://', 'wss://').replace('ws.html','ws/topology');
+                this.ws = new WebSocket(location);
+
+                this.ws.onopen = function() {
+                    server._send("Hi there!");
+                };
+
+                this.ws.onmessage = function(m) {
+                    if (m.data) {
+                        $('#log').append(m.data).append($('<br/>'));
+                    }
+                };
+
+                this.ws.onclose = function(m) {
+                    this.ws = null;
+                };
+            },
+
+            _send : function(message) {
+                if (this.ws) {
+                    this.ws.send(message);
+                }
+            },
+
+            send : function(text) {
+                if (text != null && text.length > 0) {
+                    server._send(text);
+                }
+            }
+        };
+    </script>
+</head>
+<body>
+<pre id='log'></pre>
+
+<script type='text/javascript'>
+    server.connect();
+</script>
+
+</body>
+</html>