For some reason, this reminds me of way-back when Pointcast was all the rage. Pointcast had a lot of potential (but the API was flawed). Twitter has demonstrated its potential. XMPP servers might not only make a better Twitter but help bring it to the mainstream (twitter - "Mom, pick me up at school")

I think so. For this kind of application, you probably want it tight directly to your list of contacts. Maybe this is the killer application for XMPP based instant messaging ?

OK, I've read Twitter has heart-stopping SMS usage bills (they use 3rd party gateways). XMPP client for OpenSocial/Android/iPhone anyone? We need to break the strangehold of SMS/Phone company gateways.

I would like to write an XMPP client at least for the iPhone, but we are waiting for the native SDK from Apple. For Android, we are waiting for the first devices. But sure it will come.

Note that this type of archictecture could also apply very well to reddit like systems ;)

It can also be applied to p2p music sharing =) http://www.reble.fm

Ah yes, I forgot about this use case :)

XML..... why???????????????????????????????????????????????

This is how the XMPP protocol as been designed. It is very powerful and most of all extensible, most likely thanks to the use of XML. If something is not in the protocol, you can add it for your own need.

raw text or json is even more extensible than XML. And about half as verbose, less prone to errors, easier to write parsers for etc etc....

That's not true. We have implemented multicast during the Google summer of Code (See for example of the related patch: https://support.process-one.net/browse/EJAB-329). It being test and optimised but works today if you apply the patch. It will be in ejabberd 2.1.

It is implemented in the server for multiple things, including pubsub and multi-user chat.

That's an improvement, however, after looking at it I must say that that's not multicast. This is multiple recipients for a message.

You shouldn't need to address the recipients, presence already involves people subscribing to your "presence channel". Thus your homeserver should know how to distribute the efficiently - for example by multicast. XEP-0033 just adds redundancy.

Multicast only works on either something as esoteric as the MBONE or on a local LAN/WAN. It isn't out there on the general internet, it requires too much state in the routers, so it never took off.

The original comment was not on transport level multicast, but on application level multicast. This is the one implement in ejabberd patches and thus works over Internet, not only LAN/WAN.

Transport-level mcast requires special routers.. Ah! No wonder I couldn't get the MBone videoconferencing stuff to work with Trumpet Winsock, years ago

The server knows how to distribute the message to multiple recipient and does that by itself. The client has of course nothing to do. ejabberd does that automatically for presence, but also for Multi-user chat and pubsub.

It wouldn't have been my choice for a messaging protocol either, but it's hard to argue with the huge number of extensions XMPP has grown.