docs: synchronized void stop(){
          if(status.equals("stopped"))
              return;
          long t = System.currentTimeMillis();
          run = false;
  
          try {
              serverSocket.close();
          } catch (IOException e) {
              throw S1SystemError.wrap(e);
          }
  
          executor.shutdown();
          while (!executor.isTerminated()) {
          }
  
          status = "stopped";
          LOG.info("Node "+nodeId+" file server stopped ("+(System.currentTimeMillis()-t)+" ms.)");
      }