Hi,
I just checked in support for system.getCapabilities and added standard error codes (I hope I didn't miss any places). The stuff beyond the basic protocol now lives in extensions.lisp, and there are some tests (not comprehensive at all, but it's a start). Lastly, it's now possible to send symbols over the wire; they are encoded as strings.
I've now officially run out of things to implement in the code; perhaps I'll write a manual next (depending on the weather and enthusiasm on the weekend, and on Sven's willingness to accept texinfo).
Cheers,
Rudi