code: public void writeObject (ObjectOutputStream out)
          throws IOException
      {
          // make a note of the time at which we were packed
          _packStamp = System.currentTimeMillis();
  
          // the time spent between unpacking the ping and packing the pong is the processing delay
          if (_pingStamp == 0L) {
              log.warning("Pong response written that was not constructed with a valid ping stamp",
                          "rsp", this);
              _processDelay = 0;
          } else {
              _processDelay = (int)(_packStamp - _pingStamp);
          }
  
          out.defaultWriteObject();
      }
docs: Writes our custom streamable fields.