Develop Reference

Keep socket connection open in webview on Android

I have a web app that is now being used in an Android app by launching it in a webview. Most of the Android functionality is native & the webview part is mainly just for communication via socket.io
It all works okay but as soon as the phone goes to sleep it kills the socket connection after a few minutes. This connection is used for incoming messaging so I need the connection to stay alive.
I tried creating a foreground service and using it as a keep-alive but since the socket connection is in the webview, it still gets closed no matter what I do i.e. the service stays alive and I can make a new network connection, but I can't keep the existing app connection alive.
Is there a way to keep a webview socket connection alive when the phone dozes? Am I doing something wrong? Or is my design flawed and I need a different approach?

Android SocketIO still works in background

I am creating an Android application with Socket IO
But I checked from log, the socket is not disconnected when app go to background, I don't need to use socket when app is in background. So, is it correct? Does it drain battery much when socket still works in background?
If I want to force disconnect socket in background, how can I do it?
Thanks for reading this

Android long-during TCP socket connection failure after some time

i'm writing a client-server application which uses TCP socket connection. In my android project, Service creates a thread for listening the TCP socket.
Everything seems OK. But i have got one problem.. My network service running in background fine; But some time later (10-15 min..), when i try to open my application (main activity) again, I can't get responses from the socket connection. It freezes or something?? i cant send or get TCP messages from the socket.. What can be the reason of this? I'm working on my phone, via 3G connection.
(Besides, the app running in the emulator hasn't got such this problem; I assume Its connection is stable, long-during )
Thank you for your answering.

Due to power optimizations and perhaps changes in connectivity (GPRS/HSDPA/Wifi) it's very likely your connection is being dropped.
In order to maintain a connection, your background service needs to claim a wakelock using the PowerManager class. This prevents the device from going to power-saving mode and thus disconnecting your socket. But beware, this significantly lowers the battery life of the device.
Also, you need to handle changes in connectivity which break your open connection. Android sends out a broadcast message named android.net.conn.CONNECTIVITY_CHANGE to notify of changes in connectivity.
Depending on your use-case I would poll with when the device is in the sleep-mode and only build a connection when the device is actively in use or just use C2DM push notifications

When I have experienced something like this in my apps, it has usually been because of power optimisations on the phone (which cant be overridden). If the socket has been idle for too long, it is automatically closed and needs to be reopened.

Are you sending data from time to time? Like implementing a heartbeat protocol ? if you are not, you should...or maybe it has to do with socket READ/WRITE TIMEOUT

Android Bluetooth & WakeLock relationship

I'm working on an Android application that runs in the background and enables support for a Bluetooth accessory. I would like to be constantly listening in the background for the Bluetooth device to try and open a socket to the phone. My question is whether it is possible to achieve this without constantly keeping a partial wakelock, since that would obviously have severe battery consequences. So what I'm wondering is what effect Bluetooth has on the phone falling asleep. Does the phone stay awake when there is an open Bluetooth socket? Does the Bluetooth chip wake up Android automatically if a device tries to connect? I've attempted to do some testing to answer these questions, but it's difficult to isolate what is happening with wake locks; in addition, I don't know if I can rely on the behavior I observe or if it subject to change on other devices.

Yes, if your application is running and a thread is in serverSocket.accept() method, incoming connection wake up phone, so there is no need to use wakelocks. However, make sure that your service is in foreground and is not killed by system.

If you are developing it for devices target to marshmallow based or above, there is DOZE mode to treat such conditions. You then need not to worry about these thing. It can handle the WAKE_LOCK with appropriate mechanism.

The phone does not stay awake if there is an open Bluetooth socket, and neither does the Bluetooth chip wake up Android if a device tries to connect. Usually there is a background thread running to accept connections on the open port and as soon as a device tries to connect, it is this thread which reads the connection, gets some sort of authentication from the incoming device(I am assuming that there is a security protocol in place to accept any new incoming connections) and once the incoming connection is authenticated, an independent thread is created/notified to handle subsequent information exchange with this thread.
So the background process would consume some power and battery drain and it is also responsible for keeping Android partially awake(partially as its a background process and you can always control how frequently it checks for incoming connections). Usually this background process is not run always, its run only when Bluetooth is turned on in Android. So you can also create a thread which should run only when Bluetooth is switched on in Android, else it should sleep.

Life time of QTcpSocket

I'm currently developping an Android application which connects to a server through TCP. The server is written in Qt and runs on a computer.
In server side, I use a QTcpServer and the signal QTcpServer::newConnection() to get the QTcpSocket newly connected with QTcpServer::nextPendingConnection(). I have implemented a class I called SocketManager, which manages the data received by this socket.
In Android side, I use java Socket to connect to the server.
All work great. When the Android side disconnects from the server, my SocketManager object is well notified and destroys itself. But I would like to manage properly the case when for example the Android device goes to offline or is turned off. In that case, I'm not notified of the disconnection of Android. I connect these signals of my QTcpSocket:
QAbstractSocket::disconnected(),
QAbstractSocket::stateChanged(QAbstractSocket::SocketState)
QAbstractSocket::error(QAbstractSocket::SocketError)
QObject::destroyed(QObject*), thinking that perhaps the QTcpSocket is internally destroyed by the QTcpServer.
But no signal is received when the Android device goes offline or is turned off.
When the QTcpSocket will be released by the QTcpServer? Only when the socket is explicitely disconnected? So in my case, will it never be destroyed? Should I manage the disconnection in all cases in the Android side?
Thanks everyone.

TCP will not notify you of disconnections unless the remote peer explicitly sends disconnect request (by using close() or shutdown() methods) or you try to write to a disconnected socket (in which case you get a broken pipe signal)
The classical way to solve this problem is implementing a heartbeat messaging system where after a certain amount of heartbeat inactivity you close the socket concluding that the remote peer has died suddenly or there is a network problem.