code: public void setRestartMarker(RestartData restartData)
          throws IOException, ServerException {
          Command cmd = new Command("REST", restartData.toFtpCmdArgument());
          Reply reply = null;
          try {
              reply = controlChannel.exchange(cmd);
          } catch (FTPReplyParseException e) {
              throw ServerException.embedFTPReplyParseException(e);
          }
  
          if (!Reply.isPositiveIntermediate(reply)) {
              throw ServerException.embedUnexpectedReplyCodeException(
                                  new UnexpectedReplyCodeException(reply));
          }
      }
docs: Sets restart parameter of the next transfer.
  
  @param     restartData marker to use
  @exception ServerException if the file does not exist or
  an error occured.