Dial-up server is set up! Unfortunately, contractors are working on my kitchen floor, and the phone cable I had placed for testing runs just outside of the kitchen. I removed the cable from the conduit to be safe; even if it was a cheap cable, I'd rather have it out of their way.
Tomorrow they should be done, and at that point I'll be moving this and a few other cables back to the living room. At that point, I should be able to take my Dreamcast online!