add ping and pong events

src/test/java/io/socket/client/SocketTest.java

@@ -11,6 +11,7 @@ import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
 
 import static org.hamcrest.CoreMatchers.*;
+import static org.hamcrest.Matchers.greaterThan;
 import static org.junit.Assert.assertThat;
 
 @RunWith(JUnit4.class)
@@ -60,6 +61,43 @@ public class SocketTest extends Connection {
         assertThat(id.isPresent(), is(false));
     }
 
+    @Test(timeout = TIMEOUT)
+    public void pingAndPongWithLatency() throws URISyntaxException, InterruptedException {
+        final BlockingQueue<Object> values = new LinkedBlockingQueue<Object>();
+        socket = client();
+        socket.on(Socket.EVENT_CONNECT, new Emitter.Listener() {
+            @Override
+            public void call(Object... objects) {
+                final boolean[] pinged = new boolean[] { false };
+                socket.once(Socket.EVENT_PING, new Emitter.Listener() {
+                    @Override
+                    public void call(Object... args) {
+                        pinged[0] = true;
+                    }
+                });
+                socket.once(Socket.EVENT_PONG, new Emitter.Listener() {
+                    @Override
+                    public void call(Object... args) {
+                        long ms = (long)args[0];
+                        values.offer(pinged[0]);
+                        values.offer(ms);
+                    }
+                });
+            }
+        });
+        socket.connect();
+
+        @SuppressWarnings("unchecked")
+        boolean pinged = (boolean)values.take();
+        assertThat(pinged, is(true));
+
+        @SuppressWarnings("unchecked")
+        long ms = (long)values.take();
+        assertThat(ms, greaterThan((long)0));
+
+        socket.disconnect();
+    }
+
     @Test(timeout = TIMEOUT)
     public void shouldChangeSocketIdUponReconnection() throws URISyntaxException, InterruptedException {
         final BlockingQueue<Optional> values = new LinkedBlockingQueue<Optional>();

src/test/resources/server.js

@@ -10,7 +10,7 @@ if (process.env.SSL) {
   server = require('http').createServer();
 }
 
-var io = require('socket.io')(server);
+var io = require('socket.io')(server, { pingInterval: 2000 });
 var port = process.env.PORT || 3000;
 var nsp = process.argv[2] || '/';
 var slice = Array.prototype.slice;