MQTT从主题接收消息

Question

i'm writing a program that receiving message from MQTT broker The server get ID from client and make it become name of topic: topic1, topic2 for examples. Then when subscribe, the server pass the topic's name and then read message from that topic. This is my server:

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();
        } 
      }
    }

'And this is my subscribe class

public class Subscribe implements MqttCallback {

    private final int qos = 1;
    static String topic=null;

    private MqttClient client;

    String subText = "abc";
    public Subscribe(String topic) throws MqttException, URISyntaxException {
        this.topic=topic;

        String host = "tcp://m14.cloudmqtt.com:19484"; 
        String username = "***";
        String password = "********";
        String clientId = MqttClient.generateClientId(); 
        MqttConnectOptions conOpt = new MqttConnectOptions(); 
        conOpt.setCleanSession(true);
        conOpt.setUserName(username);
        conOpt.setPassword(password.toCharArray());



        this.client = new MqttClient(host, clientId, new MemoryPersistence()); 

   ;
        this.client.setCallback(this);

        this.client.connect(conOpt);
        this.client.subscribe(topic,1);
        System.out.println("subscribe topic: " +this.topic);
    }





    /**
     * @see MqttCallback#connectionLost(Throwable)
     */
    public void connectionLost(Throwable cause) {
        System.out.println("Connection lost because: " + cause);
        System.exit(1);
    }

    /**
     * @see MqttCallback#deliveryComplete(IMqttDeliveryToken)
     */
    public void deliveryComplete(IMqttDeliveryToken token) { 
    }

    /**
     * @throws IOException 
     * @see MqttCallback#messageArrived(String, MqttMessage)
     */

    public void messageArrived(String topic, MqttMessage message) throws MqttException, IOException {
         System.out.println("1");
        subText = message.getPayload().toString();

        System.out.println("Received"+subText);

    }
}

The topic in subscribe constructor is correct, however, the this.client.setCallback(this) seem to not call the method messageArrived. So i can not receive anything.

Anybody know about it? Thank you so much

Answer 1

You don't post enough about your subscriber but here's a simple working one:

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()));
   }
}