无法接收已发布的消息以在 mqtt paho 上订阅主题

我正在使用 paho 发送和接收 mqtt 消息。到目前为止，发送消息没有任何问题。我在接收它们时遇到问题。我的代码是：

     package BenchMQTT;

     import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
     import org.eclipse.paho.client.mqttv3.IMqttToken;
     import org.eclipse.paho.client.mqttv3.MqttCallback;
     import org.eclipse.paho.client.mqttv3.MqttException;
     import org.eclipse.paho.client.mqttv3.MqttMessage;
     import org.eclipse.paho.client.mqttv3.MqttClient;

     public class Test_A_2 implements MqttCallback {

     MqttClient clientR;
     MqttClient clientS;

     public Test_A_2() {
     }

     public static void main(String[] args) throws InterruptedException {
         long startTime = System.currentTimeMillis();
         new Test_A_2().doDemo();
         long endTime = System.currentTimeMillis();
     }

    public void doDemo() throws InterruptedException {
    try {   
    clientS = new MqttClient("tcp://mybroker:1883", "Sender");
    clientR = new MqttClient("tcp://mybroker:1883", "Reiever");
    clientR.connect();
    clientS.connect();
    MqttMessage message = new MqttMessage();

    String messagePayload = "qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjk"
            + "lzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghj"
            + "klzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfgh"
            + "jklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfg"
            + "hjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasd"
            + "fghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopas"
            + "dfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopa"
            + "sdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiop"
            + "asdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuio"
            + "pasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyui"
            + "opasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyu"
            + "iopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwerty"
            + "uiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwert"
            + "nmqwertyuiop";

    clientR.subscribe("BenchMQTT");   
    clientR.setCallback(this);

    for(int i=0;i<10;i++)
    {
    message.setPayload((messagePayload)
            .getBytes());
    System.out.println(i);
    clientS.publish("BenchMQTT", message);
    }
    clientR.disconnect();   
    clientS.disconnect();
    clientR.close();   
    clientS.close();

   } catch (MqttException e)
    {
     System.out.println("ERROR");
    }
 }

     @Override
     public void connectionLost(Throwable cause) {
         // TODO Auto-generated method stub

     }

     @Override
     public void messageArrived(String topic, MqttMessage message)
     {
         System.out.println("Received: " + message.toString());
     }

     @Override
     public void deliveryComplete(IMqttDeliveryToken token) {

     }

     }

这发送和接收消息。

OUTPUT:

0
Received: 0
1
Received: 1
2
Received: 2
3
Received: 3
4
Received: 4
5
Received: 5
6
Received: 6
7
Received: 7
8
Received: 8
9
Received: 9

我想发送消息，然后接收它们。有什么帮助吗？ 预期输出：

0
1
2
3
4
5
6
7
8
9
Received: 0
Received: 1
Received: 2
Received: 3
Received: 4
Received: 5
Received: 6
Received: 7
Received: 8
Received: 9

这不是 MQTT（或任何发布/订阅消息传递）的工作原理，如果接收者连接到服务器，则消息将在发送时传递。

例外情况是，如果接收方连接并订阅了 QOS 大于 0 的主题，然后断开连接并稍后重新连接（没有设置干净会话标志），则将传递已发布的 QOS 大于 0 的丢失消息在重新连接时。

另一种可能性是，如果消息已在保留标志设置为 true 的情况下发布，但只有发布到主题的最后一条消息才会在接收客户端订阅时传递。