anchor.diff:            completer.complete(event);
           }
         } catch(e) {
  -        print("Service error: $e ${e.stackTrace}");
  +        printError("Service error", e);
         }
       });
       return completer.future;
  
positive.code:         completer.complete();
        }
      }).catchError((e) {
        print("service error: $e ${e.stackTrace}");
      });
      return completer.future;
    }
  
negative.code:       try {
          _handleMessage(event);
        } catch(e) {
          printError("Service error", e);
        }
      });
    }
  