[Android] Bluetooth

1. Docs
   
   • Bluetooth (Fundamentals & samples)
     http://developer.android.com/guide/topics/wireless/bluetooth.html
   • Samples
     BluetoothChat
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2. Four major tasks
   
   • Set up Bluetooth
   • Find devices that are either paired or available in the local area
   • Connect devices
   • Transfer data between devices.
3. Important Classes
   
   • BluetoothAdapter
   • BluetoothDevice
   • BluetoothServerSocket
     
   • BluetoothSocket
     Notes:
     If the two devices have not been previously paired, then the Android framework will automatically show a pairing request notification or dialog to the user during the connection procedure.
     
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4. Flow Char
   
   • Prepare
     Check to see if Bluetooth is supported/disabled;
     Enable Bluetooth
     
   • As server
     BluetoothAdapter--------->BluetoothServerSocket----<accept>---->BluetoothSocket-------->Input/OutputStream
   • As client
     BluetoothAdapter--------->Devices Address String-------->BluetoothDevice---->BluetoothSocket-------->BluetoothSocket-------->Input/OutputStream
     
     or
     
     BluetoothAdapter--------->BluetoothDevice---->BluetoothSocket-------->BluetoothSocket[connected]-------->Input/OutputStream
     
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5. Monitor Bluetooth state
   (From: http://developer.android.com/guide/topics/wireless/bluetooth.html)
   Listen for the ACTION_STATE_CHANGED broadcast Intent, which the system will broadcast whenever the Bluetooth state has changed. This broadcast contains the extra fields EXTRA_STATE and EXTRA_PREVIOUS_STATE, containing the new and old Bluetooth states, respectively. Possible values for these extra fields are STATE_TURNING_ON, STATE_ON, STATE_TURNING_OFF, and STATE_OFF. Listening for this broadcast can be useful to detect changes made to the Bluetooth state while your app is running.
   
6. About UUID
   When to invoke the following methods, an argument of UUID need to provided,
   
   - BluetoothAdapter: Create BluetoothServerSocket
   a) BluetoothServerSocket listenUsingInsecureRfcommWithServiceRecord(String name, UUID uuid)
   b) BluetoothServerSocket listenUsingRfcommWithServiceRecord(String name, UUID uuid)
   
   - BluetoothDevice: Create BluetoothSocket
   a) BluetoothSocket createInsecureRfcommSocketToServiceRecord(UUID uuid)
   b) BluetoothSocket createRfcommSocketToServiceRecord(UUID uuid)
   
   If you specify your own UUID when to create BluetoothServerSocket on server side by invoking listenUsingInsecureRfcommWithServiceRecord/listenUsingRfcommWithServiceRecord, you must specify the same UUID when to connect to the server by invoking createInsecureRfcommSocketToServiceRecord/createRfcommSocketToServiceRecord.
   
   But, if you are connecting to a Bluetooth serial board then try using the well-known SPP UUID 00001101-0000-1000-8000-00805F9B34FB.
   
   (More details:
   - http://developer.android.com/guide/topics/wireless/bluetooth.html, see "Connecting Devices" section;
   - http://developer.android.com/reference/android/bluetooth/BluetoothAdapter.html, see description of mehtods listenUsingInsecureRfcommWithServiceRecord/listenUsingRfcommWithServiceRecord;
   - http://developer.android.com/reference/android/bluetooth/BluetoothDevice.html, see description of methods createInsecureRfcommSocketToServiceRecord/createRfcommSocketToServiceRecord.)
   
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