XMPP is a real-time messaging protocol that allows clients to exchange messages and presence information over XML streams. It provides a bidirectional communication channel that servers can use to push updates to clients, avoiding the need for polling. XMPP defines core semantics for establishing streams, authenticating users, and sending message and presence stanzas. These can be extended through XMPP Extension Proposals to support new use cases like voice calls, file sharing, and building web services that communicate in real-time. Popular applications of XMPP include instant messaging, chat applications, and Comet-style web APIs.
1. XMPP in Real-Time Applications
Ben Weaver
@bwvr
http://benweaver.com/
2. INTRODUCTION
+ What is XMPP?
+ Why is it “real-time”?
+ How does it work?
+ Where can you use it?
+ Conclusion
3. WHAT: OVERVIEW
+ XMPP is the Extensible Messaging and Presence Protocol
+ Routes messages among clients.
+ Broadcasts presence (status) to interested contacts.
+ The “X” in extensible is XML.
+ Since XML has namespaces...
+ You can invent new message types any time.
4. WHAT: HISTORY
+ Back in 1998...
+ ICQ and AOL Instant Messenger were popular IM services.
+ Microsoft and Yahoo! were releasing their own.
+ Jeremie Miller started Jabber: community driven IM
+ Jabber standardization began in 1999
+ In 2002, an IETF working group formalized XMPP
5. WHAT: EXAMPLE
<?xml version=“1.0”?>
<stream to=“example.com”> <?xml version=“1.0”?>
<stream from=“example.com”>
<features>
... negotiate features ... <starttls />
<mechanisms />
</features>
<message from=“juliet@example.com”
to=“romeo@example.net”>
<body>Art thou not Romeo...</body>
</message> <message from=“romeo@example.net”
to=“juliet@example.com”>
<body>Art thou not Romeo...</body>
</stream> </message>
</stream>
Client Server
6. WHY: AJAX
+ I work on web sites and applications.
+ AJAX is a common technique used to improve experience.
+ Each call is a connection + HTTP request.
- This is cumbersome when making frequent requests.
- (Although, some browsers support Keep-Alive).
+ Communication is client-driven
- Servers can’t push; polling adds overhead.
- Awkward for web applications.
7. WHY: BI-DIRECTIONAL
+ XMPP is a bi-directional stream.
+ XML stanzas add structure.
+ IQ stanzas provide REST-like semantics.
+ XMPP is “non-blocking”: use an event-driven style.
+ BOSH extends XMPP to the web.
8. HOW: OVERVIEW
+ XMPP comes in two parts.
- Core: stream-level semantics
- Jabber: use the Core for IM
+ XEP: make your XMPP extensions official.
9. HOW: CORE
+ RFC 3920 defines stream semantics.
+ Clients are identified as user@host/resource
+ <stream />: root element
+ <features />: bootstrap the stream
- TLS: secure communication
- SASL: flexible authentication
+ <message />: send a message
+ <iq id=“unique-token” type=“get|set|...” />: info query
- Unique token identifies responses.
- Body can be anything.
+ <presence />: broadcast your status
10. HOW: INSTANT MESSAGE
+ RFC 3921 defines how IM works with the Core.
+ Each account has a roster.
- Track clients connected through same account.
- Store contacts and permissions.
+ Presence
- States are defined.
- Notification is regulated through rosters.
+ Message semantics are defined.
11. HOW: EXTEND
+ A stream is a sequence of XML stanzas.
+ Invent new ones!
+ Submit an XMPP Extension Proposal (XEP).
+ Some examples:
- Ping <http://xmpp.org/extensions/xep-0199.html>
- Jingle <http://xmpp.org/extensions/xep-0166.html>
- BOSH <http://xmpp.org/extensions/xep-0124.html>
12. WHERE: WEB SERVICE
+ BOSH: Bi-directional streams over Synchronous HTTP
+ Like Comet
+ Define “HTML” semantics for XMPP stream.
+ Example: <http://github.com/thisismedium/python-xmpp-
server/blob/master/examples/_bosh.py>
13. WHERE: CHAT
+ Chat example
+ <http://github.com/thisismedium/python-xmpp-server/
blob/master/examples/chat-server.py>
14. CONCLUSION
+ Lot’s of people make clients; check it out!
+ Bi-directional
+ Event-driven
+ Works on the web
