AFAICT, the SIP protocol has no agreed upon conventions for registering display-names or other meta-data. That is, while you can attach display-names to just about every URI, there's nothing stating which URI's display name should be considered canonical when parsing a registration request. For now I'm assuming I should display the contact field's display name. (For the non-technical readers, yes, I do realise that sounded somewhat like Greek).

Anyway, 4 hours of effort, 1.5 on that silly client error, and then 2.5 of non-stumped work, with probably half of that being my trying to learn just enough SIP to get the job done. I've got the iteration across registered users working (which is the "core" of the problem), but haven't yet made some needed modifications to allow the server to store more information than it does by default (particularly the display-names (it stores just the contact field's URL, discarding the display-name after it goes to all the work of extracting it (sigh))).

Keep running into things where I'm not sure if I'm actually coding things wrong or if I just don't know how SIP is supposed to work. It probably would have been more expensive to do the learning up front (given how little of SIP we want to use), but probably would have been less frustrating for me :) .

Oh well, seem pretty close to getting the SIP back-end done for the demo... the rest is just web-site development.