code: protected IncomingFileTransfer createIncomingFileTransfer(
              FileTransferRequest request) {
          if (request == null) {
              throw new NullPointerException("ReceiveRequest cannot be null");
          }
  
          IncomingFileTransfer transfer = new IncomingFileTransfer(request,
                  fileTransferNegotiator);
          transfer.setFileInfo(request.getFileName(), request.getFileSize());
  
          return transfer;
      }
docs: When the file transfer request is acceptable, this method should be
  invoked. It will create an IncomingFileTransfer which allows the
  transmission of the file to proceed.
  
  @param request
  The remote request that is being accepted.
  @return The IncomingFileTransfer which manages the download of the file
  from the transfer initiator.