XMPP Intro 1101 - 2008

XMPP intro E

Extensible Messaging and Presence
Protocol

Steffen Larsen (slarsen@nordija.com)

XMPP - what is it?
• Extensible Messaging and Presence
Protocol

• An Open Source Instant Messaging
(IM) system. I would also like to refer
to it as a session protocol.

• Easy integration of extensions
• Widely used and many implementations
of the core system.

XMPP clients

• Pidgin (formerly known as gaim, all)
• Adium (based on pidgin lib.,mac)
• GTalk (Google Talk, m$ windoze)
• psi (all)
• gajim (all), etc... MANY!

XMPP core

• Going from Jabber (1999) to XMPP
• XMPP foundation, founded 2003. For
standardization.

• RFC 3920, RFC 3921 (deﬁne XML
stream, login and architecture)

XMPP core

• XMPP is a XML streaming standard
• XMPP deﬁnes a <stream/> to make a
stream session.

• TLS (authentication) / SASL (Simple
Authentication and Security Layer)

XMPP core

core consists of the following:

• <stream/>
• Addressing standard (JIDs):
user@host.domain/resource. This is
important for the routing/prioritizing.

• stanzas

XML Streams
• <stream/> container for XML
elements in a stream.

• <stream/> once in a session, send
many xml elements!

• <stream/> consists of:
• negotiation of TLS and SASL
• stanzas

The “layers”

• TCP (your socket!)
• TLS secure layer
• SASL negotiation
• XMPP (send/receive stanzas)
• Third party channel.. (initiated by XMPP, voice
etc)

Using the language
• Logging in <stream>, TLS, SASL..
• SASL for negotiating diff.
encryption mechanisms.

• Challenge/Response..
• server binds the client resource
• fetching the buddy list.. <iq get
roster..>

• sending stanzas messages, presence
etc.

Language Elements

• XMPP have 3 XML stanzas. (well
structured children under the
<stream/> element):
• <presence/>
• <message/>
• <iq/> (Information, Query: get, set)

XML Stream example
Basic sessions:

|--------------------| C: <?xml version='1.0'?>
| <stream> | <stream:stream
|--------------------| to='example.com'
| <presence> | xmlns='jabber:client'
| <show/> | xmlns:stream='http://etherx.jabber.org/streams'
| </presence> | version='1.0'>
|--------------------| S: <?xml version='1.0'?>
| <message to='foo'> | <stream:stream
| <body/> | from='example.com'
| </message> | id='someid'
|--------------------| xmlns='jabber:client'
| <iq to='bar'> | xmlns:stream='http://etherx.jabber.org/streams'
| <query/> | version='1.0'>
| </iq> | ... encryption, authentication, and resource binding ...
|--------------------| C: <message from='juliet@example.com'
| ... | to='romeo@example.net'
|--------------------| xml:lang='en'>
| </stream> | C: <body>Art thou not Romeo, and a Montague?</body>
|--------------------| C: </message>
S: <message from='romeo@example.net'
to='juliet@example.com'
xml:lang='en'>
S: <body>Neither, fair saint, if either thee dislike.</body>
S: </message>
C: </stream:stream>
S: </stream:stream>

XMPP Stanzas
<message/>
<message
from='northumberland@shakespeare.lit/westminster'
id='richard2-4.1.247'
to='kingrichard@royalty.england.lit/throne'>
<body>My lord, dispatch; read o'er these articles.</body>
<request xmlns='urn:xmpp:receipts'/>
</message>

<iq/>
Example: Client requests current roster from server:

<iq from='juliet@example.com/balcony' type='get' id='roster_1'>
<query xmlns='jabber:iq:roster'/>

e.g. get roster </iq>
Example: Client receives roster from server:

at startup <iq to='juliet@example.com/balcony' type='result' id='roster_1'>
<query xmlns='jabber:iq:roster'>
<item jid='romeo@example.net'
name='Romeo'
subscription='both'>
<group>Friends</group>
</item>
<item jid='mercutio@example.org'
name='Mercutio'
subscription='from'>
</item>
<item jid='benvolio@example.org'
name='Benvolio'
subscription='both'>
</item>
</query>
</iq>

XMPP Architecture
server - server. xmpp registar with cert.

client - client

XMPP Architecture

server- Text
Text
client-gw-
SIP

XMPP Extensions (XEP)

• XMPP deﬁnes a set of XEPs
• Deﬁnition of an extension (XEP-001).
XEP relies on namespaces.
• XEP-166, XEP-167 (Jingles), XEP-176
important right now
• Feature and service discovery
important. Can also be done in

XMPP Platforms

• ejabberd (erlang)
• xﬁre (uses smack-lib, java based)
• google talk (based on libjingle, c++).
Can connect to the base XMPP
architecture and vice versa. Some
XEPs are NOT the same (voice/video/
ice)!

XMPP Libraries
• Libjingle (google, c++, not compliant to
some xmpp extensions)

• Perl:XMPP (perl!, dah!)
• LibIksmeal (C, very unorganized!)
• Smack (Java, JMF!)
• My own!... :-) (core in libpurple, plugin
lib for xep-166,167,176)

XMPP in the future?
• Will it become a de-facto
standard? (xmpp is what http
was in the past)

• New extensions?
• XEP-666 for set top boxes? ;-)
• XEP for Conferencing?

XMPP links:

• www.xmpp.org
• http://www.xmpp.org/rfcs/rfc3920.htm
• http://www.xmpp.org/rfcs/rfc3921.htm
• http://www.xmpp.org/extensions/

Questions?
If you don’t have any:

• when is xep-166 etc.
(jingle) a standard?

• where do I start?
• ....

XMPP Intro 1101 - 2008

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XMPP Intro 1101 - 2008