Ytukyg

I have the following part of code:

    package com.company;



import org.eclipse.paho.client.mqttv3.*;

import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;



import javax.security.auth.callback.Callback;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;



public class Main implements MqttCallback {

    private static String sTopic;

    private static int iQos;

    private static MqttClient mqttClient;

    private static String sUsername;

    private static Frame frame = new Frame();



    public static void main(String args) throws MqttException {



        frame.getConnect().addActionListener(new ActionListener() {

            @Override

            public void actionPerformed(ActionEvent e) {

                int iPort;

                String sIp = frame.getBrokerAddressValue();

                sUsername = frame.getUsernameValue();

                try {

                    String broker = "tcp://"; //bridge and host

                    iPort = frame.getPortValue();

                    broker+=sIp+":"+iPort;

                    mqttClient = new MqttClient(broker, sUsername, new MemoryPersistence());  //URI, ClientId, Persistence

                    MqttConnectOptions connectOptions = new MqttConnectOptions();

                    connectOptions.setCleanSession(true);

                    System.out.println("Connecting to broker: "+broker);

                    mqttClient.connect();



                    System.out.println("Connected");

                }catch (NumberFormatException exc){

                    System.out.println("Wrong port format");

                } catch (MqttException e1) {

                    e1.printStackTrace();

                }



            }

        });



        frame.getSubscribe().addActionListener(new ActionListener() {

            @Override

            public void actionPerformed(ActionEvent e) {

                sTopic = frame.getTopicValue();

                try {

                    mqttClient.subscribe(sTopic);

                } catch (MqttException e1) {

                    e1.printStackTrace();

                }

                System.out.println("Subscribed");

            }

        });



        frame.getPublish().addActionListener(new ActionListener() {

            @Override

            public void actionPerformed(ActionEvent e) {

                String sMessage = frame.getMessageValue();

                MqttMessage message = new MqttMessage(sMessage.getBytes());

                iQos = frame.getQosValue();

                message.setQos(iQos);

                try {

                    mqttClient.publish(sTopic,message);

                } catch (MqttException e1) {

                    e1.printStackTrace();

                }

                System.out.println("Message published");

            }

        });

    }



    @Override

    public void connectionLost(Throwable throwable) {



    }



    @Override

    public void messageArrived(String topic, MqttMessage message) throws Exception{

        frame.getTextArea().setText(String.valueOf(message));

    }



    @Override

    public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {



    }

}

Here's a part of my realization of the mqtt client. Method getConnect is processing a click on button 'Connect', method getSubscribe is processesing a click on button 'Subscribe', method getPublish is processing a click on button 'Publish'.The problem is the following: when I subscribe on the topic, messages don't arrive on the clients, which are subscribed on this topic. What's the matter?

If I understand your question correctly,You are subscribed to a topic 'sTopic' but you are not receiving messages when some one publish message to the topic 'sTopic'.

Are you sure Mqtt client is connected successfully to broker ? Make mqtt client is connected before making subscribe call.

            if( mqttClient.isConnected()) {

                mqttClient.subscribe(sTopic);

             }

and same applies for publish also.

               if( mqttClient.isConnected()) {

                   mqttClient.publish(sTopic,message);

                }

Once if these call goes, you should see published messages in messageArrived call back method.

You need to set the callback method to mqttClient

                clientCallback = new MqttCallback() {



                    @Override

                    public void connectionLost(Throwable cause) {



                    }



                    @Override

                    public void messageArrived(String topic, MqttMessage message) throws Exception {



                    }



                    @Override

                    public void deliveryComplete(IMqttDeliveryToken token) {



                    }

                };



                mqttClient.setCallback(clientCallback);