private async Task DownloadFile(byte[] message)
 {
     var dto = MessagePackSerializer.Deserialize <FileDto>(message);
     await FileTransferService.ReceiveFile(dto.Buffer,
                                           dto.FileName,
                                           dto.MessageId,
                                           dto.EndOfFile,
                                           dto.StartOfFile);
 }
 private void OpenFileTransferWindow(Viewer viewer)
 {
     FileTransferService.OpenFileTransferWindow(viewer);
 }