Android : Creating dataoutputstream in service inside?

I have a service Class, in which the socket is created. I can call the service at MainActivity, but I want to use in MainActivity button inside to pass data.I created dataoutputstream in service,But I do not know how to make the data can be transmitted over Button,Do not create dataoutputstream in service, and then use a similar global variables to make butoon able to pass data?

In Service :

public class SocketService extends Service {
public static final String TAG = "MySocket";
public static Socket socket;
public static DataOutputStream out = null;
@Override
public IBinder onBind(Intent intent) {
    return null;
}
@Override  
public void onCreate() {  
    super.onCreate();     
    Log.d(TAG, "onCreate() executed");  
}  

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    Log.d(TAG, "onStartCommand() executed");
    new Thread(new Runnable() {  
        @Override  
        public void run() {  
            try {                               
                socket = new Socket("ip",port);
                Log.d(TAG,"creat socket");
                out = new DataOutputStream(socket.getOutputStream());//and stream
                Log.d(TAG,"dataoutput stream");
            } catch (UnknownHostException e1) {
                e1.printStackTrace();
                Log.d(TAG,"UnknownHostException error");
            } catch (IOException e1) {
                e1.printStackTrace();
                Log.d(TAG,"IOException error");
            }
        }  
    }).start();  
    return super.onStartCommand(intent, flags, startId);  
} 
@Override
public void onDestroy() {
    try {
        socket.close();
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    socket = null;
    super.onDestroy();
}

}

data:

Button.OnClickListener BtnPowOnClickListener = new Button.OnClickListener(){
    @Override
    public void onClick(View view) {    
        try {
            byte[] buf ={(byte) 0x80,                         
                    };                                                              
            out.write(buf);
            out.flush();                                                
        }catch(Exception obj){ 
        }       
    }
};