anchor.diff:    List<Socket> clientSockets = [];
     Map<String, List<Map> > requestors = {};
     Map<String, Map> currentLock = {};
  -  Completer _done;
  -
  -  Future get closed => _done.future;
   
     Locker.config(this.serverSocket);
   
  
positive.code:         .then((ServerSocket sSocket) {
            Locker locker = new Locker.config(sSocket);
            locker.serverSocket.listen(locker.handleClient);
            locker._done = new Completer();
            return locker;
          });
  
  
negative.code:      Future.wait([
         Future.wait(clientSockets.map((s) => s.close())),
         serverSocket.close()
       ]);
  
  }
  