Firebase Listener does not identify or resume connection after idle time

Question

My project is to identify whether the client is online or offline. I use the code made available in the Android-Firebase documentation, which uses an EventListener in ".info / connected".

// since I can connect from multiple devices, we store each connection instance separately
// any time that connectionsRef's value is null (i.e. has no children) I am offline
final FirebaseDatabase database = FirebaseDatabase.getInstance();
final DatabaseReference myConnectionsRef = database.getReference("users/joe/connections");

// stores the timestamp of my last disconnect (the last time I was seen online)
final DatabaseReference lastOnlineRef = database.getReference("/users/joe/lastOnline");

final DatabaseReference connectedRef = database.getReference(".info/connected");
connectedRef.addValueEventListener(new ValueEventListener() {
  @Override
  public void onDataChange(DataSnapshot snapshot) {
    boolean connected = snapshot.getValue(Boolean.class);
    if (connected) {
      DatabaseReference con = myConnectionsRef.push();

      // when this device disconnects, remove it
      con.onDisconnect().removeValue();

      // when I disconnect, update the last time I was seen online
      lastOnlineRef.onDisconnect().setValue(ServerValue.TIMESTAMP);

      // add this device to my connections list
      // this value could contain info about the device or a timestamp too
      con.setValue(Boolean.TRUE);
    }
  }

  @Override
  public void onCancelled(DatabaseError error) {
    System.err.println("Listener was cancelled at .info/connected");
  }
});

This method correctly identifies when the user terminates or reopens the application or when minor disconnections occur on the internet. However, I did a test turn off the Wifi of the device for a time of 2 minutes, it is identified in the Firebase Database that is not connected, but when I turn on the Wifi, resuming the internet connection, Firebase does not recognize the active connection, appears as if the user still remained inactive.

This code snippet was inserted into the onCreate method of my MainActivity.

Can anyone tell me why this occurs?

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EDIT: Attachments

Error log:

11-14 10:12:55.272 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Trying to fetch auth token

11-14 10:12:55.276 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Successfully fetched token, opening connection

11-14 10:12:55.281 27901-27926/com.example.davi.projetofirebase D/Connection: conn_14 - Opening a connection

11-14 10:12:55.293 27901-27926/com.example.davi.projetofirebase D/WebSocket: ws_14 - WebSocket error. bkx: unknown host: s-usc1c-nss-208.firebaseio.com at bku.d(:com.google.android.gms.DynamiteModulesC@11746448:102) at bkv.run(:com.google.android.gms.DynamiteModulesC@11746448:4) at java.lang.Thread.run(Thread.java:760) Caused by: java.net.UnknownHostException: s-usc1c-nss-208.firebaseio.com at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:174) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:356) at java.net.Socket.connect(Socket.java:586) at com.android.org.conscrypt.OpenSSLSocketImpl.connect(OpenSSLSocketImpl.java:265) at com.android.org.conscrypt.OpenSSLSocketImpl.connect(OpenSSLSocketImpl.java:252) at java.net.Socket.(Socket.java:427) at java.net.Socket.(Socket.java:210) at javax.net.ssl.SSLSocket.(SSLSocket.java:906) at com.android.org.conscrypt.OpenSSLSocketImpl.(OpenSSLSocketImpl.java:192) at com.android.org.conscrypt.OpenSSLSocketFactoryImpl.createSocket(OpenSSLSocketFactoryImpl.java:68) at bku.d(:com.google.android.gms.DynamiteModulesC@11746448:94) at bkv.run(:com.google.android.gms.DynamiteModulesC@11746448:4)  at java.lang.Thread.run(Thread.java:760) 

11-14 10:12:55.294 27901-27926/com.example.davi.projetofirebase D/WebSocket: ws_14 - closing itself

11-14 10:12:55.295 27901-27926/com.example.davi.projetofirebase D/Connection: conn_14 - Realtime connection failed

11-14 10:12:55.295 27901-27926/com.example.davi.projetofirebase D/Connection: conn_14 - closing realtime connection

11-14 10:12:55.295 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Got on disconnect due to OTHER

11-14 10:12:55.296 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Scheduling connection attempt

11-14 10:12:55.297 27901-27926/com.example.davi.projetofirebase D/ConnectionRetryHelper: Scheduling retry in 27403ms

11-14 10:12:55.304 27901-27926/com.example.davi.projetofirebase D/WebSocket: ws_14 - closed

11-14 10:13:02.947 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Connection interrupted for: connection_idle

11-14 10:13:02.960 27901-27926/com.example.davi.projetofirebase D/ConnectionRetryHelper: Cancelling existing retry attempt

Answer 1

I contacted the support team Firebase, they informed me a solution that apparently solved my problem:

Apparently the listener for .info / connected stops listening if there is no active action or listener for the database. I added another helper listener to any one node in my database, and it worked!

DatabaseReference myConnectionRef2 = database.getReference("/users/joe/lastOnline");
myConnectionRef2.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        if (dataSnapshot.getValue() == null) {
            System.out.println("FIREBASE: Aux connected");
        } else {
            System.out.println("FIREBASE: Aux not connected");
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

Every time I lose the network connection, the two listeners try to resume communication until the network is reconnected.

Thanks to everyone who helped me solve this problem.

Answer 2

As Franks says, if you enable debug logging for the client, will be able for sure to see the state of the connection, whether the client is reestablishing its connection or not.

public synchronized void setLogLevel (Logger.Level logLevel)

By default, this is set to INFO. This includes any internal errors (ERROR) and any security debug messages (INFO) that the client receives. Set to DEBUG to turn on the diagnostic logging, and NONE to disable all logging.