I was testing MQTT for a project. I am also able to receive messages on a topic to which my client had subscribed when the client is connected. I have set QoS to 1 and cleanSession is set to false. But I am unable to receive messages which were sent to the subscribed topic when my client connects again. In my application almost all the work is done by a helper service.
Here is my code
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:screenOrientation="portrait" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service
android:name=".MqttHelperService"
android:enabled="true"
android:exported="true" />
<!-- MqttService -->
<service android:name="org.eclipse.paho.android.service.MqttService" />
</application>
MainActivity.java
package com.prateek.mqtttest;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
startService(new Intent(getBaseContext(), MqttHelperService.class));
}
}
MqttHelperService.java
package com.prateek.mqtttest;
import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.widget.Toast;
import org.eclipse.paho.android.service.MqttAndroidClient;
import org.eclipse.paho.client.mqttv3.IMqttActionListener;
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.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
public class MqttHelperService extends Service implements MqttCallback {
private static final String MQTT_URI = "tcp://broker.mqttdashboard.com:1883";
private static final String CLIENT_ID = "prateek";
private static final String MQTT_TOPIC = "mqttmessenger";
private static final int QOS = 1;
private MqttAndroidClient client;
public MqttHelperService() {
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(this, "MQTT Helper Service Started", Toast.LENGTH_SHORT).show();
new Thread(new Runnable() {
@Override
public void run() {
connect();
}
}, "MqttHelperService").start();
return START_STICKY;
}
public class MqttHelperBinder extends Binder {
public MqttHelperService getService(){
return MqttHelperService.this;
}
}
public void connect() {
client = new MqttAndroidClient(this, MQTT_URI, CLIENT_ID);
client.setCallback(this);
try {
MqttConnectOptions options = new MqttConnectOptions();
options.setCleanSession(false);
client.connect(options, new IMqttActionListener() {
@Override
public void onSuccess(IMqttToken iMqttToken) {
Toast.makeText(getBaseContext(), "connected to MQTT broker", Toast.LENGTH_SHORT).show();
subscribe();
}
@Override
public void onFailure(IMqttToken iMqttToken, Throwable throwable) {
Toast.makeText(getBaseContext(), "failed to connect: " + throwable.getMessage(), Toast.LENGTH_SHORT).show();
}
});
} catch (MqttException e) {
Toast.makeText(this, "could not connect to MQTT broker at " + MQTT_URI, Toast.LENGTH_SHORT).show();
}
}
public void subscribe() {
try {
IMqttToken token = client.subscribe(MQTT_TOPIC, QOS, null, new IMqttActionListener() {
@Override
public void onSuccess(IMqttToken iMqttToken) {
Toast.makeText(getBaseContext(), "subscription successful", Toast.LENGTH_SHORT).show();
}
@Override
public void onFailure(IMqttToken iMqttToken, Throwable throwable) {
Toast.makeText(getBaseContext(), "subscription failed: " + throwable, Toast.LENGTH_SHORT).show();
}
});
} catch (MqttException e) {
Toast.makeText(this, "could not subscribe", Toast.LENGTH_SHORT).show();
}
}
@Override
public IBinder onBind(Intent intent) {
// TODO: Return the communication channel to the service.
throw new UnsupportedOperationException("Not yet implemented");
}
@Override
public void connectionLost(Throwable throwable) {
Toast.makeText(this, "connection lost", Toast.LENGTH_SHORT).show();
}
@Override
public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
Toast.makeText(this, "message received on topic " + s, Toast.LENGTH_SHORT).show();
}
@Override
public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
}
@Override
public void onDestroy() {
super.onDestroy();
Toast.makeText(this, "Service Destroyed", Toast.LENGTH_SHORT).show();
}
}
I even checked this link With the clear session flag set to FALSE, I am missing the published values but could not find the error in my code
I've had a same problem recently. Now I think the solution is very simple, but I've spent many many hours to figure it out.
This line was 'bad':
The 'correct' is:
If you call the connect method with 2 parameters, you are using this constructor:
Instead of the right one:
I hope that is your problem too.