/**
 * download list of registered users from server at cmd.eyedbits.com
 * 
 * @return list of users
 */
static Vector<String> downloadUserList() {
  Log.i(TAG, String.format("Downloading UserList"));
  
  String serverUrl = SERVER_URL + SERVER_URL_QUERYUSERLIST;

  //TODO: implement multiple tries with exponential backoff if server is not responding		
  DefaultHttpClient hc = new DefaultHttpClient();
  ResponseHandler <String> res = new BasicResponseHandler();
  HttpGet getMethod = new HttpGet(serverUrl);

  Vector<String> retVector = new Vector<String>(); 
  try {
    String response = hc.execute(getMethod, res);
    Log.i(TAG, "Http response: " + response);
    // todo check if successfull and not error
    
    // parse string
    try {
      JSONArray jsonArray = new JSONArray(response);
      for (int i = 0; i < jsonArray.length(); ++i) {
        JSONObject row = jsonArray.getJSONObject(i);
        String userName = row.getString("UserName");
        retVector.add(userName);
      }
    } catch (JSONException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    
  } catch (ClientProtocolException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
  } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
  }
  
  return retVector;
}