Add ping pong test for causal order UDP broadcasts

.travis.yml

@@ -23,6 +23,7 @@ script:
     - scripts/test rx.broadcast.integration.BasicOrderUdpBroadcastTest
     - scripts/test-table-tennis rx.broadcast.integration.pp.PingPongUdpBasicOrder
     - scripts/test-table-tennis rx.broadcast.integration.pp.PingPongUdpSingleSourceFifoOrder
+    - scripts/test-table-tennis rx.broadcast.integration.pp.PingPongUdpCausalOrder
 deploy:
     provider: script
     script: scripts/deploy

src/main/java/rx/broadcast/VectorTimestamp.java

@@ -8,6 +8,11 @@ final class VectorTimestamp {
 
     private long[] timestamps;
 
+    @SuppressWarnings("unused")
+    VectorTimestamp() {
+
+    }
+
     VectorTimestamp(final long[] ids, final long[] timestamps) {
         if (ids.length != timestamps.length) {
             throw new IllegalArgumentException("IDs and timestamps must contain the same number of elements");

src/test/java/rx/broadcast/integration/pp/PingPongUdpCausalOrder.java

@@ -0,0 +1,92 @@
+package rx.broadcast.integration.pp;
+
+import org.junit.Test;
+import rx.Observable;
+import rx.broadcast.Broadcast;
+import rx.broadcast.CausalOrder;
+import rx.broadcast.UdpBroadcast;
+import rx.observers.TestSubscriber;
+
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.net.SocketException;
+import java.net.UnknownHostException;
+import java.util.concurrent.TimeUnit;
+
+@SuppressWarnings({"checkstyle:MagicNumber", "checkstyle:AvoidInlineConditionals"})
+public class PingPongUdpCausalOrder {
+    private static final int MESSAGE_COUNT = 100;
+
+    private static final long TIMEOUT = 30;
+
+    /**
+     * Receive a PING and respond with a PONG.
+     * @throws SocketException if the socket could not be opened, or the socket could not bind to the given port.
+     * @throws UnknownHostException if no IP address for the host machine could be found.
+     */
+    @Test
+    public final void recv() throws SocketException, UnknownHostException {
+        final int port = System.getProperty("port") != null
+            ? Integer.valueOf(System.getProperty("port"))
+            : 54321;
+        final int destinationPort = System.getProperty("destinationPort") != null
+            ? Integer.valueOf(System.getProperty("destinationPort"))
+            : 12345;
+        final DatagramSocket socket = new DatagramSocket(port);
+        final InetAddress destination = System.getProperty("destination") != null
+            ? InetAddress.getByName(System.getProperty("destination"))
+            : InetAddress.getByName("localhost");
+        final Broadcast broadcast = new UdpBroadcast<>(socket, destination, destinationPort, new CausalOrder<>());
+        final TestSubscriber<Ping> subscriber = new TestSubscriber<>();
+
+        broadcast.valuesOfType(Ping.class)
+            .doOnNext(System.out::println)
+            .concatMap(ping ->
+                broadcast.send(new Pong(ping.value))
+                    // Once we've sent the response, we can emit the PING value to the subscriber.
+                    // The cast here is a hack to allow us to concatenate a PING onto the stream.
+                    // Where this is an `Observable<Void>` we know we won't get anything that needs to be casted.
+                    .cast(Ping.class)
+                    .concatWith(Observable.just(ping))
+                    .doOnCompleted(() -> System.out.println("Sent PONG")))
+            .take(MESSAGE_COUNT)
+            .subscribe(subscriber);
+
+        subscriber.awaitTerminalEventAndUnsubscribeOnTimeout(TIMEOUT, TimeUnit.SECONDS);
+        subscriber.assertNoErrors();
+        subscriber.assertValueCount(MESSAGE_COUNT);
+    }
+
+    /**
+     * Send a set PING messages to the receiver, expecting PONG messages in response.
+     * @param args the command line arguments passed to the program
+     * @throws SocketException if the socket could not be opened, or the socket could not bind to the given port.
+     * @throws UnknownHostException if no IP address for the host machine could be found.
+     */
+    public static void main(final String[] args) throws InterruptedException, SocketException, UnknownHostException {
+        final int port = System.getProperty("port") != null
+            ? Integer.valueOf(System.getProperty("port"))
+            : 54321;
+        final int destinationPort = System.getProperty("destinationPort") != null
+            ? Integer.valueOf(System.getProperty("destinationPort"))
+            : 12345;
+        final DatagramSocket socket = new DatagramSocket(port);
+        final InetAddress destination = System.getProperty("destination") != null
+            ? InetAddress.getByName(System.getProperty("destination"))
+            : InetAddress.getByName("localhost");
+        final Broadcast broadcast = new UdpBroadcast<>(socket, destination, destinationPort, new CausalOrder<>());
+
+        Observable.range(1, MESSAGE_COUNT)
+            .map(Ping::new)
+            .doOnNext(System.out::println)
+            .concatMap(value ->
+                broadcast.send(value)
+                    .doOnCompleted(() -> System.out.printf("Sent %s%n", value))
+                    .cast(Pong.class)
+                    .concatWith(broadcast.valuesOfType(Pong.class).first()))
+            .timeout(TIMEOUT, TimeUnit.SECONDS)
+            .toBlocking()
+            .subscribe(pong ->
+                System.out.printf("Received %s%n", pong));
+    }
+}