// Disable retries on message sending failure.
producer.setRetryTimesWhenSendAsyncFailed(0);
// Set the number of messages to send.
int messageCount = 10;
final CountDownLatch countDownLatch = new CountDownLatch(messageCount);
for (int i = 0; i < messageCount; i++) {
     try {
             final int index = i;
             // Create a message instance and set the topic and message content.
             Message msg = new Message(topic_name, "TAG", ("Hello rocketMq " + index).getBytes(RemotingHelper.DEFAULT_CHARSET));
             producer.send(msg, new SendCallback() {
                     @Override
                     public void onSuccess(SendResult sendResult) {
                             // Logic for successful message sending.
                             countDownLatch.countDown();
                             System.out.printf("%-10d OK %s %n", index, sendResult.getMsgId());
                     }

                     @Override
                     public void onException(Throwable e) {
                             // Logic for failed message sending.
                             countDownLatch.countDown();
                             System.out.printf("%-10d Exception %s %n", index, e);
                             e.printStackTrace();
                     }
             });
     } catch (Exception e) {
             e.printStackTrace();
     }
}
countDownLatch.await(5, TimeUnit.SECONDS);

for (int i = 0; i < 10; i++) {
     // Create a message instance and set the topic and message content.
     Message msg = new Message(topic_name, "TAG", ("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET));
     // Send a one-way message.
     producer.sendOneway(msg);
}

// Instantiate a consumer.
DefaultLitePullConsumer pullConsumer = new DefaultLitePullConsumer(
     namespace,                                               
     groupName,                                             
     new AclClientRPCHook(new SessionCredentials(accessKey, secretKey)));
// Set the NameServer address.
pullConsumer.setNamesrvAddr(nameserver);
// Set to start consumption from the first offset.
pullConsumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);

// Subscribe to a topic.
pullConsumer.subscribe(topic_name, "*");
// Start the consumer instance.
pullConsumer.start();
try {
     System.out.printf("Consumer Started.%n");
     while (true) {
             // Pull messages.
             List<MessageExt> messageExts = pullConsumer.poll();
             System.out.printf("%s%n", messageExts);
     }
} finally {
     pullConsumer.shutdown();
}