It is a paper copy, but I can make a scan for you. I think tiu.c might be all. The TIU ("terminal access unit") was the network card, so to speak (actually some 5 boards in a rack) and did a lot of the heavy lifting. From the tiu.c file I understand that a DR11-B parallel I/O card was used on the PDP side to connect to the TIU, and that access was structured as a block device driver. Looks like it. I think that in the lifespan of Spider (1972-1978) there were 3 main network programs (basing myself on McIlroy's Unix Reader): - 'nfs' an FTP-like program to copy files to/from a central File Store. I'm not sure whether the File Store was a Unix machine or something else. - 'ufs' not sure what it was, but I think a telnet-like facility - 'npr' a network printing program A little surprising, but no reference to a Spider mail program in that document. Thanks! It is from October 1973, which sounds right for Spider. I guess this code is the first networking on Unix, predating the UoI work by about 18 months.