My important experience---android position

1.add <uses-permission android:name="android.permission.CALL_PHONE" /> in <manifest.xml> if you want to use android to call; 

2.add  <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> if want to use GPS ;

3.add <uses-permission android:name="android.permission.INTERNET" /> if want to use socket;

4.can get the ostream & istream only if the socket has connected to the server;