Matt Wood (we really need to sort him out his own login) gives an update on his XMPP experiements...
I've made a little time recently to move my previous XMPP experiments forward a little. Here are the
I've started echoing the stream of text that passes across the little
screens of DAB radios into XMPP space. We call it 'live text' and it's
frequently entered by production staff in a studio as a show is actually
being broadcast, so it's timely but with a very short half-life. Seemed like
a good fit for XMPP delivery!
You can find the live text at grouphug.hellomatty.com: point your client
at the group chats at firstname.lastname@example.org,
email@example.com, firstname.lastname@example.org... Feel free
to hook this into your own applications...
The backend was again written with XMPP4R which I'm still finding very
easy to work with.
We currently use a very lightweight but proprietary protocol and server
to get this text into the Flash widgets for iPlayer and the radio network
sites. On the assumption that it would be just better to use an open
protocol for this I'm hoping to spend some time with Tsung soon to see whether we
can make XMPP scale comparably. If you've any scaling war stories I'd really
like to hear them - to be competitive we'll need to support at least 100,000
concurrent clients without breaking a sweat.
By popular request I've switched federation on at hug.hellomatty.com -
this means you no longer need a hug.hellomatty.com account to subscribe to
the now playing and live text streems - just use your regular jid or gmail
Paul asked me whether XMPP could go through firewalls and the answer is
YES. This is
important if you've a large client base any number of whom may be behind a
corporate firewall that only allows 'safe' traffic through. The BOSH spec
allows you to tunnel XMPP over HTTP in a way that doesn't hammer your server
in a polling frenzy but which still respects timely content deliver and
which plays nicely with proxies.
I've hacked together a couple of small demos to show how this works, and
on top of JSJaC, a compact
and robust XMPP client library which handles the BOSH mechanics for you -
your code sees a single, 'persistent' connection object. These
implementations are pretty naive and I'm going to maintain that this is to
make the code as easy to follow as possible.
Very Live Text!
pulls the live text for Radio 4 into your browser and hopefully shows how
little code you need to script XMPP from your browser. It also shows you how
to do 'anonymous' logins, and how to work with JSJaC's callback-based
tracks the 'now playing' feed I presented last time. Here you can see basic
support for the XMPP extensions you need to get 'user tunes' working
(rosters, entity capabilities and personal eventing via pubsub) layered on
top of JSJaC.
I also noticed that the tune spec was updated to allow you to publish
your rating of the tune that's currently playing. So with this app you can
click 'Pop!' or 'Drop!' buttons to publish your (dis-)pleasure with our
playlists. From a public service perspective a federated standard for
scrobbling certainly seems kind of interesting, especially if you worry
about who owns your attention profile.
Next up is some benchmarking with Tsung, and I've a couple more toys in
the pipeline. More here as it happens...
Your comments are, of course, very welcome!