McastTestVerticle.java

import org.vertx.java.core.Handler;
import org.vertx.java.core.AsyncResult;
import org.vertx.java.core.AsyncResultHandler;
import org.vertx.java.core.datagram.DatagramPacket;
import org.vertx.java.core.datagram.DatagramSocket;
import org.vertx.java.core.datagram.InternetProtocolFamily;
import org.vertx.java.platform.Verticle;
import org.vertx.java.core.buffer.Buffer;

import java.util.concurrent.atomic.AtomicInteger;

public class McastTestVerticle extends Verticle {

    public void start() {

        final Buffer buffer = new Buffer("foo");
        final String groupAddress = "230.0.0.1";
        final AtomicInteger receivedCount = new AtomicInteger(0);

        final DatagramSocket peer1 = vertx.createDatagramSocket(null);
        final DatagramSocket peer2 = vertx.createDatagramSocket(InternetProtocolFamily.IPv4);

        peer2.dataHandler(new Handler<DatagramPacket>() {
                @Override
                public void handle(DatagramPacket event) {
                    System.out.println("RCVD: " + event.data().toString());
                    System.out.println("COUNT: " + receivedCount.getAndIncrement());

                }
            });

        vertx.setPeriodic(100, new Handler<Long>() {
                public void handle(Long ignored) {
                    System.out.println("receivedCount is " + receivedCount.get());
                    peer1.send(buffer, groupAddress, 1234, null);
                }
            });

        peer2.listen("127.0.0.1", 1234, new AsyncResultHandler<DatagramSocket>() {
                @Override
                public void handle(AsyncResult<DatagramSocket> event) {

                    peer2.listenMulticastGroup(groupAddress, new AsyncResultHandler<DatagramSocket>() {
                            @Override
                            public void handle(AsyncResult<DatagramSocket> event) {
                                System.out.println("Joined group");
                                //stay in the group for two seconds
                                vertx.setTimer(2000, new Handler<Long>() {
                                        public void handle(Long ignored) {
                                            System.out.println("Leaving group");
                                            peer2.unlistenMulticastGroup(groupAddress, null);
                                        }
                                    });
                            }
                        });
                }
            });
    }
}