Java MQTT从主题接收消息

我正在编写一个从MQTT代理接收消息的程序 服务器从客户端获取ID并使其成为主题的名称：例如，topic1、topic2。 然后在订阅时，服务器传递主题的名称，然后从该主题读取消息。 这是我的服务器：

public class AnalyticServer {

      // The server socket.
      private static ServerSocket serverSocket = null;
      // The client socket.
      private static Socket clientSocket = null;

      // This server can accept up to maxClientsCount clients' connections.
      private static final int maxClientsCount = 5;
      private static final clientThread[] threads = new clientThread[maxClientsCount];

      public static void main(String args[]) throws MqttException, InterruptedException {





        // The default port number.
        int portNumber = 4544;

        //Open Server
        try {
          serverSocket = new ServerSocket(portNumber);
        } catch (IOException e) {
          System.out.println(e);
        }
        //


        //When server is listening
        System.out.println("Server is now listening at port 4544");
        while (true) {
          try {
            //Make connection 

            clientSocket = serverSocket.accept();

            System.out.println("Connected");



            int i = 0;
            //Find thread null to run the connection
            for (i = 0; i < maxClientsCount; i++) {
              if (threads[i] == null) {
                (threads[i] = new clientThread(clientSocket, threads)).start();
                break;
              }
            }
            if (i == maxClientsCount) {
              PrintStream os = new PrintStream(clientSocket.getOutputStream());
              os.println("Server is now, please try again later");
              os.close();
              clientSocket.close();
            }
          } catch (IOException e) {
            System.out.println(e);
          }
        }
      }
    }

    //Thread control each Request
    class clientThread extends Thread {


      private Socket clientSocket = null;
      private final clientThread[] threads;
      private int maxClientsCount;

      public clientThread(Socket clientSocket, clientThread[] threads) {
        this.clientSocket = clientSocket;
        this.threads = threads;
        maxClientsCount = threads.length;
      }

      public void run() {
        int maxClientsCount = this.maxClientsCount;
        clientThread[] threads = this.threads;


        try {
            int identifier=0;
            //get id
             InputStream input = null;
             input = clientSocket.getInputStream();


             identifier=input.read();

             String topic="topic".concat(String.valueOf(identifier));

            //Subscribe
             try {
                System.out.println("subscribing");
                Subscribe receive=new Subscribe(topic);


            } catch (MqttException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (URISyntaxException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } 
             // open image
             FileInputStream imgPath = new FileInputStream("image.jpg");
             BufferedImage bufferedImage = ImageIO.read(imgPath);

             Thread.sleep(1200);
             ByteArrayOutputStream baos = new ByteArrayOutputStream();
             ImageIO.write( bufferedImage, "jpg", baos );
             baos.flush();
             byte[] imageInByte = baos.toByteArray();
             baos.close();



          //SendImage
          DataOutputStream outToClient = new DataOutputStream(clientSocket.getOutputStream());        
          outToClient.write(imageInByte);
          System.out.println(outToClient.size());

          clientSocket.close();

        } catch (IOException e) {
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } 
      }
    }

subscribe构造函数中的主题是正确的，但是this.client.setCallbackthis似乎没有调用messageArrived方法。所以我什么也收不到

有人知道吗？

---

非常感谢

关于您的订阅者，您的帖子还不够多，但这里有一个简单的实用方法：

import java.io.IOException;
import java.sql.Timestamp;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MqttDefaultFilePersistence;

public class TestSub implements MqttCallback
{
   public static void main(String[] args)
   {
      String url = "tcp://iot.eclipse.org:1883";
      String clientId = "TestSub_"+System.currentTimeMillis();
      String topicName = "test/ABC/one";
      int qos = 1;
      boolean cleanSession = true;
      String userName = "myUserId";
      String password = "mypwd";

      try
      {
         new TestSub(url, clientId, cleanSession, userName, password, topicName, qos);
      }
      catch (MqttException me)
      {
         System.out.println(me.getLocalizedMessage());
         System.out.println(me.getCause());
         me.printStackTrace();
      }
   }

   public TestSub(String url, String clientId, boolean cleanSession, String userName, String password, String topicName, int qos) throws MqttException
   {
      String tmpDir = System.getProperty("java.io.tmpdir");
      MqttDefaultFilePersistence dataStore = new MqttDefaultFilePersistence(tmpDir);
      MqttClient         client;
      MqttConnectOptions conOpt;

      try
      {
         conOpt = new MqttConnectOptions();
         conOpt.setMqttVersion(MqttConnectOptions.MQTT_VERSION_DEFAULT);
         conOpt.setCleanSession(cleanSession);
         if (userName != null)
            conOpt.setUserName(userName);

         if (password != null)
            conOpt.setPassword(password.toCharArray());

         // Construct an MQTT blocking mode client
         client = new MqttClient(url, clientId, dataStore);

         // Set this wrapper as the callback handler
         client.setCallback(this);

         // Connect to the MQTT server
         client.connect(conOpt);
         System.out.println("Connected to " + url + " with client ID " + client.getClientId());

         System.out.println("Subscribing to topic \"" + topicName + "\" qos " + qos);
         client.subscribe(topicName, qos);

         // Continue waiting for messages until the Enter is pressed
         System.out.println("Press <Enter> to exit");
         try
         {
            System.in.read();
         }
         catch (IOException e)
         {
            // If we can't read we'll just exit
         }

         // Disconnect the client from the server
         client.disconnect();
         System.out.println("Disconnected");

      }
      catch (MqttException e)
      {
         e.printStackTrace();
         System.out.println("Unable to set up client: " + e.toString());
         System.exit(1);
      }
   }

   public void connectionLost(Throwable cause)
   {
      System.out.println("Connection lost! " + cause.getLocalizedMessage());
      System.exit(1);
   }

   public void deliveryComplete(IMqttDeliveryToken token)
   {
   }

   public void messageArrived(String topic, MqttMessage message)
         throws MqttException
   {
      String time = new Timestamp(System.currentTimeMillis()).toString();
      System.out.println("Time:\t" + time + "  Topic:\t" + topic + "  Message:\t" + new String(message.getPayload()));
   }
}

---

您已将用户名和密码包含在源代码中，最好的办法是删除该问题并使用该信息再次询问。hiddenoh我忘记了，非常感谢。@ngoc anh该信息仍在编辑历史记录中。完全删除问题并再次提问。还要更改该用户的密码

import java.io.IOException;
import java.sql.Timestamp;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MqttDefaultFilePersistence;

public class TestSub implements MqttCallback
{
   public static void main(String[] args)
   {
      String url = "tcp://iot.eclipse.org:1883";
      String clientId = "TestSub_"+System.currentTimeMillis();
      String topicName = "test/ABC/one";
      int qos = 1;
      boolean cleanSession = true;
      String userName = "myUserId";
      String password = "mypwd";

      try
      {
         new TestSub(url, clientId, cleanSession, userName, password, topicName, qos);
      }
      catch (MqttException me)
      {
         System.out.println(me.getLocalizedMessage());
         System.out.println(me.getCause());
         me.printStackTrace();
      }
   }

   public TestSub(String url, String clientId, boolean cleanSession, String userName, String password, String topicName, int qos) throws MqttException
   {
      String tmpDir = System.getProperty("java.io.tmpdir");
      MqttDefaultFilePersistence dataStore = new MqttDefaultFilePersistence(tmpDir);
      MqttClient         client;
      MqttConnectOptions conOpt;

      try
      {
         conOpt = new MqttConnectOptions();
         conOpt.setMqttVersion(MqttConnectOptions.MQTT_VERSION_DEFAULT);
         conOpt.setCleanSession(cleanSession);
         if (userName != null)
            conOpt.setUserName(userName);

         if (password != null)
            conOpt.setPassword(password.toCharArray());

         // Construct an MQTT blocking mode client
         client = new MqttClient(url, clientId, dataStore);

         // Set this wrapper as the callback handler
         client.setCallback(this);

         // Connect to the MQTT server
         client.connect(conOpt);
         System.out.println("Connected to " + url + " with client ID " + client.getClientId());

         System.out.println("Subscribing to topic \"" + topicName + "\" qos " + qos);
         client.subscribe(topicName, qos);

         // Continue waiting for messages until the Enter is pressed
         System.out.println("Press <Enter> to exit");
         try
         {
            System.in.read();
         }
         catch (IOException e)
         {
            // If we can't read we'll just exit
         }

         // Disconnect the client from the server
         client.disconnect();
         System.out.println("Disconnected");

      }
      catch (MqttException e)
      {
         e.printStackTrace();
         System.out.println("Unable to set up client: " + e.toString());
         System.exit(1);
      }
   }

   public void connectionLost(Throwable cause)
   {
      System.out.println("Connection lost! " + cause.getLocalizedMessage());
      System.exit(1);
   }

   public void deliveryComplete(IMqttDeliveryToken token)
   {
   }

   public void messageArrived(String topic, MqttMessage message)
         throws MqttException
   {
      String time = new Timestamp(System.currentTimeMillis()).toString();
      System.out.println("Time:\t" + time + "  Topic:\t" + topic + "  Message:\t" + new String(message.getPayload()));
   }
}