code: private MessageBuffer getNextBuffer()
              throws IOException
      {
          MessageBuffer next = in.next();
          if (next == null) {
              throw new MessageInsufficientBufferException();
          }
          assert (buffer != null);
          totalReadBytes += buffer.size();
          return next;
      }
docs: Get the next buffer without changing the position
  
  @return
  @throws IOException