Added reader endpoint description to WebSocket.md (#729)

* Added reader endpoint description to WebSocket.md

* Fixed sample code in WebSocket.md

* Use on('message',listener) in node.js sample code

site/docs/latest/clients/WebSocket.md

@@ -50,7 +50,7 @@ $ bin/pulsar-daemon start websocket
 
 ## API Reference
 
-Pulsar's WebSocket API offers two endpoints, one for [producing](#producer-endpoint) messages and one for [consuming](#consumer-endpoint) messages.
+Pulsar's WebSocket API offers three endpoints for [producing](#producer-endpoint) messages, [consuming](#consumer-endpoint) messages and [reading](#reader-endpoint) messages.
 
 All exchanges via the WebSocket API use JSON.
 
@@ -150,6 +150,50 @@ Key | Type | Required? | Explanation
 `messageId`| string | yes | Message ID of the processed message
 
 
+### Reader endpoint
+
+The reader endpoint requires you to specify a {% popover property %}, {% popover cluster %}, {% popover namespace %}, and {% popover topic %} in the URL:
+
+{% endpoint ws://broker-service-url:8080/ws/reader/persistent/:property/:cluster/:namespace/:topic %}
+
+##### Receiving messages
+
+Server will push messages on the WebSocket session:
+
+```json
+{
+  "messageId": "CAAQAw==",
+  "payload": "SGVsbG8gV29ybGQ=",
+  "properties": {"key1": "value1", "key2": "value2"},
+  "publishTime": "2016-08-30 16:45:57.785"
+}
+```
+
+Key | Type | Required? | Explanation
+:---|:-----|:----------|:-----------
+`messageId` | string | yes | Message ID
+`payload` | string | yes | Base-64 encoded payload
+`publishTime` | string | yes | Publish timestamp
+`properties` | key-value pairs | no | Application-defined properties
+`key` | string | no |  Original routing key set by producer
+
+#### Acknowledging the message
+
+**In WebSocket**, Reader needs to acknowledge the successful processing of the message to
+have the Pulsar WebSocket service update the number of pending messages.
+If you don't send acknowledgements, Pulsar WebSocket service will stop sending messages after reaching the pendingMessages limit.
+
+```json
+{
+  "messageId": "CAAQAw=="
+}
+```
+
+Key | Type | Required? | Explanation
+:---|:-----|:----------|:-----------
+`messageId`| string | yes | Message ID of the processed message
+
+
 ### Error codes
 
 In case of error the server will close the WebSocket session using the
@@ -218,7 +262,30 @@ Here's an example Python {% popover consumer %} that listens on a Pulsar {% popo
 ```python
 import websocket, base64, json
 
-TOPIC = 'ws://localhost:8080/ws/producer/persistent/sample/standalone/ns1/my-topic'
+TOPIC = 'ws://localhost:8080/ws/consumer/persistent/sample/standalone/ns1/my-topic/my-sub'
+
+ws = websocket.create_connection(TOPIC)
+
+while True:
+    msg = json.loads(ws.recv())
+    if not msg: break
+
+    print "Received: {} - payload: {}".format(msg, base64.b64decode(msg['payload'])
+
+    # Acknowledge successful processing
+    ws.send(json.dumps({'messageId' : msg['messageId']}))
+
+ws.close()
+```
+
+#### Python reader
+
+Here's an example Python reader that listens on a Pulsar {% popover topic %} and prints the message ID whenever a message arrives:
+
+```python
+import websocket, base64, json
+
+TOPIC = 'ws://localhost:8080/ws/reader/persistent/sample/standalone/ns1/my-topic'
 
 ws = websocket.create_connection(TOPIC)
 
@@ -276,12 +343,27 @@ Here's an example Node.js {% popover consumer %} that listens on the same topic
 
 ```javascript
 var WebSocket = require('ws'),
-    topic = "ws://localhost:8080/ws/producer/persistent/my-property/us-west/my-ns/my-topic1",
+    topic = "ws://localhost:8080/ws/consumer/persistent/my-property/us-west/my-ns/my-topic1/my-sub",
     ws = new WebSocket(topic);
 
-ws.onmessage = function(packet) {
-	var receiveMsg = JSON.parse(packet.data);
-	var ackMsg = {"messageId" : receiveMsg.messageId};
-	ws.send(JSON.stringify(ackMsg));
-};
-```
\ No newline at end of file
+ws.on('message', function(message) {
+    var receiveMsg = JSON.parse(message);
+    console.log('Received: %s - payload: %s', message, new Buffer(receiveMsg.payload, 'base64').toString());
+    var ackMsg = {"messageId" : receiveMsg.messageId};
+    ws.send(JSON.stringify(ackMsg));
+});
+```
+
+#### NodeJS reader
+```javascript
+var WebSocket = require('ws'),
+    topic = "ws://localhost:8080/ws/reader/persistent/my-property/us-west/my-ns/my-topic1",
+    ws = new WebSocket(topic);
+
+ws.on('message', function(message) {
+    var receiveMsg = JSON.parse(message);
+    console.log('Received: %s - payload: %s', message, new Buffer(receiveMsg.payload, 'base64').toString());
+    var ackMsg = {"messageId" : receiveMsg.messageId};
+    ws.send(JSON.stringify(ackMsg));
+});
+```