I ran 0.1.7 for some time using the Twonky upnp server. The receiver.arf is included in the tRio 0.1.7.zip file, you should find it in the main directory when you unzip the archive. You need to untar the receiver.arf file into your TFTP directories (by IP number) so the Rio DAR can load the 0.1.7 client software.