XMPP Protocol
and
Application Development using
Open Source XMPP Software
and Libraries
Ozgur Ozturk
ozturk@gatech.edu
Georgia Institute of Technology, Atlanta, GA
Acknowledgement: This tutorial is based on the book “XMPP: The
Definitive Guide, Building Real-Time Applications with Jabber
Technologies” with permission from Peter Saint-Andre.
Access to This Tutorial
• Latest version of slides available on
– http://DrOzturk.com/talks
• Also useful for clicking on links
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Software
that you will need to repeat exercises with me
• Start downloads now
– In the break you will have time to install
• Visual C# 2008 Express Edition
– http://www.microsoft.com/express/downloads/
• Eclipse IDE for Java Developers (92 MB)
– http://www.eclipse.org/downloads/
• Openfire & Spark Code:
– http://www.igniterealtime.org/downloads/source.jsp
– TortoiseSVN recommended for subversion check out
• http://tortoisesvn.net/downloads
• JabberNet code:
– http://code.google.com/p/jabber-net/
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Part 1
Introduction to XMPP
What is XMPP
• Extensible Messaging and Presence Protocol
– open, XML-based protocol
– aimed at near-real-time, extensible
• instant messaging (IM), and
• presence information.
• Extended with features such as Voice over IP
and file transfer signaling
– and even expanded into the broader realm of
message-oriented middleware
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Samples from its Usage
• IM and Social Networking platforms
– GTalk, and Facebook
• Collaborative services
– Google Wave, and Gradient;
• Geo-presence systems
– Nokia Ovi Contacts
• Multiplayer games
– Chesspark
• Many online live customer support and technical
support services.
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Overview of Tutorial
•
•
•
•
Introduction to XMPP
IM and Presence requirements, XML Refresher
XMPP Extension Protocols (XEPs)
Hands on exercises/demonstrations of using
some Open Source XMPP Libraries, Clients and
Servers
• Architecture options & extending XMPP
• Talk slides, code and links will be available on
http://DrOzturk.com/talks
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SIMPLE (contender to XMPP)
• SIMPLE: SIP for Instant Messaging and
Presence Leveraging Extensions
• SIP: Session Initiation Protocol, established
signaling protocol for VOIP and IPTV
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Advantages of XMPP
• Open XML standard formalized by IETF
– Extensible for new service or information types
– Implementations with modular/pluggable APIs
• Continuously extended through the standards
process of the XMPP Standards Foundation
• XMPP servers (via federation) form a
decentralized network similar to e-mail
– anyone (with a domain) can run an XMPP server
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Some XMPP Terminology
• JabberID (JID): address of XMPP entities
– JIDs for users look like email addresses, composed
of username, “@” sign and the domain
– Bare JID + Resource Identifier = Full JID:
• e.g., ozgur7@gmail.com/web-9z2
• Routing traffic to one connection of user, web-client
rather than mobile or desktop client (which may be
simultaneously connected)
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Three Types of XMPP Stanzas
• Stanza: Basic unit of communication in XMPP
• Libraries abstract away from the XML layer
– However to extend XMPP we need to know basics
• Three types of Stanzas:
– Message
• method for getting info from one place to another
– Presence
• availability and status messages of entities
– iq (Info/Query)
• request-response interactions and simple workflows
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XML Basics
Terminology
<?xml version="1.0" encoding="ISO-8859-1"?>
<CATALOG>
• Entity, Tag
<CD>
• Schema
<TITLE>Unchain my heart</TITLE>
<ARTIST NAME="Joe Cocker" />
• DTD, XSD
<COUNTRY>USA</COUNTRY>
<COMPANY>EMI</COMPANY>
• Well-formed
<PRICE>8.20</PRICE>
• Valid
<YEAR>1987</YEAR>
</CD>
Attribute
<!– Add more CD Albums here… --> • Not recommended for data.
• Prefer to use element:
</CATALOG>
<ARTIST>
Special Syntax for empty elements,
where closing tag would come
immediately after opening tag
<NAME> Joe Crocker </NAME>
</ARTIST>
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• Recommended for metadata
Sample XML Standard: POSLog
Namespaces needed for combining multiple existing
vocabularies, to prevent conflict of names.
Namespaces are not
applied to attributes,
unless you specify them
explicitly.
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XML Namespaces
Not a URL, just a namespace!
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Same Local Name,
Different Qualified Names
<bk:bookstore
xmlns:bk="urn:xmlns:dozturk.com:books">
<bk:book bk:title="Lord of the Rings, Book 3">
<book for=“Ozgur Ozturk“/>
</bk:book>
</bk:bookstore>
These two are from two vocabularies.
One of the <book> tags means reserving.
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1: Message Stanza
• The “push” method for getting information
from one place to another
<message from="ozgur7@gmail.com/wz2"
to="stpeter@jabber.org"
type="chat">
from address
<body>How are you?</body> •not provided by
sending client,
<subject>Query</subject>
•stamped by the
</message>
sender’s server
•to avoid address
spoofing
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2: Presence Messages
• Advertises the network availability and status
messages of entities
• A specialized publish-subscribe method;
people who requested subscription to your
presence and authorized by you receive
updated presence information when you
come online, and go offline, and change your
status
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2: Presence Stanza
<presence
from="ozgur7@gmail.com/android-z2">
<show>do not disturb</show>
<status>in a meeting</status>
</presence>
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3: IQ (Info/Query) Messages
• Structure for request-response interactions
and simple workflows.
• Requests and responses are tracked using the
id attribute
• type attribute included in the exchanged iq
stanzas helps in establishing a structured IQ
interaction between two entities
• Next example: IM client software gets my
roster from its server and then updates it
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3: IQ (Info/Query) Stanza
1/4: Requesting Roster
<iq from="ozgur7@gmail.com/wz2"
id="rr82a1z7"
to="ozgur7@gmail.com"
type="get">
<query xmlns="jabber:iq:roster"/>
</iq>
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3: IQ (Info/Query) Stanza
2/4: Server Returning Roster
<iq
from="ozgur7@gmail.com"
id="rr82a1z7"
to="ozgur7@gmail.com/wz2"
type="result">
<query xmlns="jabber:iq:roster">
<item jid="frnd1@gmail.com"/>
<item jid="spouse@facebook.com"/>
</query>
• </iq>
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3: IQ (Info/Query) Stanza
3/4: Client adds a new contact.
<iq from="ozgur7@gmail.com/wz2"
id="ru761vd7"
New transaction, new id.
to="ozgur7@gmail.com"
type="set">
<query xmlns="jabber:iq:roster">
<item jid="stpeter@jabber.org"/>
</query>
</iq>
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3: IQ (Info/Query) Stanza
4/4:Server’s Acknowledgement
<iq from="ozgur7@gmail.com"
Same id with request.
id="ru761vd7"
to="ozgur7@gmail.com/wz2"
type="result“/>
Each request needs a
reply. Even if it is empty
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15 Minute Break
Now is the time to install your software
When we are back we will code, yay!
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Part 2
Coding a Basic Client
Without re-implementing the wheel:
Using Jabber-Net .Net Library
Download Link for
.Net XMPP library
• XMPP Library for .Net (written in C#)
http://code.google.com/p/jabber-net/
– I recommend to install from source code
• So you can trace into the library code upon errors
• I will show how to add components to toolbar manually
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Download and install Jabber-Net
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MyFirstClient project
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Visual Studio Toolbox
with Jabber-Net
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Simplest Client App
Double Click
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Five lines of code
• Automatically added events and function
templates:
• Just fill in the action:
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Voila! Our Weather Bot is Working
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Part 3
XMPP Extension Protocols (XEPs)
Extensibility and
Available XEPs
• XMPP is an XML based, extensible protocol
• XMPP Standards Foundation (XSF)
standardizes extensions to XMPP through a
process centered around XMPP Extension
Protocols (XEPs)
– http://xmpp.org/extensions/
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Data Forms XEP
• Specifies how a server sends the information
necessary for a client to render a form
• Defines several common field types
– boolean,
– list options with single or multiple choice,
– text with single line or multiple lines,
– hidden fields, …
– & extensibility for future data types
• Related extension: CAPTCHA Forms XEP
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In-Band Registration XEP
• For in-band registration, password change or
cancellation of an existing registration
• Extensible via use of data forms
– enables services to gather a wide range of
information during the registration process
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Multi-User Chat XEP
• To enable multiple XMPP users to exchange
messages in the context of a room or channel
– similar to Internet Relay Chat (IRC).
• Standard chat-room features such as room topics
and invitations
• A strong room control model, adds ability to:
– kick and ban users
– name room moderators and administrators
– require membership or passwords to join the room
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Publish-Subscribe XEP &
Personal Eventing Protocol (PEP) XEP
• Presents a more generalized form of the
publish/subscribe model than presence
– communicating “rich presence” such as moods
– exchanging “lifestreaming” data, such as
microblogs
– also applied to storing personal data
• Bookmarks, client preferences…
• Further extensions of PEP
– User Tune, User Location, and User Activity XEPs
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Multimedia Networking
Extensions: Jingle XEP
• XMPP as the signaling channel to negotiate,
manage & terminate media sessions
– voice/video chat, file transfer, screen sharing…
– negote media codecs, bitrates and other
parameters related to the voice format to be used,
deciding whether TCP or UDP will be used
– what IP addresses and ports will be used, etc
• Media data itself is sent either p2p or through
a media relay.
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Part 4
Compiling and Customizing
Openfire XMPP Server
and Spark Chat Client
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Download Links for
Client and Server with
Pluggable API
• OpenFire: XMPP server
• Spark: XMPP client
• Both are open source Java implementation,
with multi-platform support
• Openfire & Spark Code:
– http://www.igniterealtime.org/downloads/source.jsp
– TortoiseSVN recommended for subversion check out
• http://tortoisesvn.net/downloads
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DELETED SLIDES
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