How to make the Android device hold a TCP connection to Internet without wake lock?
I want my application to be connected to server though the mobile connection, yet allowing the device to go into sleep mode. I expect it to wake up when IP packates arrives.
How can this be done? How to receive "interrupts" from the Internet without draining battery?
Answer
When you are blocked on a read from a tcp stream the device can go into a deep sleep and when tcp traffic comes in it will briefly wakeup the device, as soon as a bit is read in you start a wakelock until you have received the whole transmission then release it.
Here is an example with web sockets, I've ran this app for over 12 hours in the background with no battery impact. https://github.com/schwiz/android-websocket-example
The client is here, the blocking read is in the start method. https://github.com/schwiz/android-websockets/blob/master/src/com/codebutler/android_websockets/HybiParser.java