[racket] Socket error with distributed places example

Hello--

I am learning about distributed places, and I tried to run the "hello
world" example found at
http://docs.racket-lang.org/distributed-places/index.html . I get the
following error:

> uncaught exception: "socket error connecting to localhost:6344"

I tried a couple of other port numbers, just in case 6344 was in use
(in fact, it was in use when I first tried it, but I killed the
program that was using it), but got the same results.

Any tips for debugging this? I suppose I can fire up Wireshark, but
... urgh. Hoping this is a common problem with common causes. Perhaps
I should mention that I am new to Racket, but having a fair amount of
experience with Scheme, I am learning in somewhat random order ... if
there is relevant documentation I ought to read, I do know how to
read, so just let me know.

Thanks!