docs: public boolean validateResponseHead() throws IOException {
          // 检查是否是正确反馈报文
          if (cmd != CmdConstants.FDFS_PROTO_CMD_RESP) {
              throw new IOException(
                      "recv cmd: " + cmd + " is not correct, expect cmd: " + CmdConstants.FDFS_PROTO_CMD_RESP);
          }
          // 获取处理错误状态
          if (status != 0) {
              throw FdfsServerException.byCode(status);
          }
  
          if (contentLength < 0) {
              throw new IOException("recv body length: " + contentLength + " < 0!");
          }
          return true;
      }