Writes to Bluetooth sockets are handled by writeNative() in android_bluetooth_BluetoothSocket.cpp. This calls asocket_write() which is implemented in abort_socket.c. This latter function sleeps until poll() indicates that the socket is writeable, then calls write() once, returning the number of bytes written. However writeNative() just returns this byte count to the caller; it's eventually ignored in BluetoothOutputStream.java. This doesn't match the semantics of a Java OutputStream, which is required to block until all bytes have been written. This fix adds a loop to writeNative() that repeatedly calls the lower level write function until all the data has been written (or an error occurred in which case we should exit the loop early). With this change it is possible to write large amounts of data to a Bluetooth socket without experiencing data loss. Change-Id: I0b464382817e15adec32ba0e3cb37e7d1cccc730