A Jabber Instant Messaging Client: Written in Java

1
A Jabber Instant Messaging Client Written in Java

• Masters Project Presentation by
• Nathan Harmon

2
Presentation Goals

• Why the Jabber protocol was created
• How the Jabber protocol works
• How the Jabber client works

3
Overview

• Introduction
• History of Instant Messaging
• The Jabber Protocol
• Client Application Design
• Demo

4
Project Purpose

• Growth of the Internet has caused a push for many
  new standards
• Net created many interoperability problems
• Data
• Operating System
• Instant Messaging clients
• Standards solutions
• eXtensible Markup Language (XML)
• Java
• Jabber

5
Project Scope

• Client in Java
• Features
• User registration
• User login/logoff
• Roster Management
• Normal messages
• Chat messages

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Technologies Used

• Jabber
• Created by Jeremie Miller
• Released as Open Source in 1999
• XML
• W3C Recommendation in Feb. 1998
• Based on HTML
• Two main APIs
• SAX
• DOM
• Java
• Created by Sun in 1995

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Overview

• Introduction
• History of Instant Messaging
• The Jabber Protocol
• Client Application Design
• Demo

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Original Instant Messaging Applications

• PLANET
• Created in 1973 by Jacques Vallee
• First chat program designed for ARPANET
• Unix talk
• Released with 4.2BSD
• Internet Relay Chat (IRC)
• Created by Jarkko Oikarinen in 1989
• Ability to join chat rooms (channels)

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ICQ/AIM

• ICQ created by Mirabilis, Ltd. in 1996
• AOL and Netscape release AOL Instant Messenger
  (AIM) in 1997
• Similar applications created by other portal
  companies
• MSN
• Yahoo!

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Client Interoperability

• Free to download Profits come from advertising
• AOL has consistently blocked connections from
  other clients
• IETF formed the Instant Messaging and Presence
  Protocol (IMPP) Working Group

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Other Jabber Clients

• Jabber Instant Messenger Jabber, Inc.
• WinJab Open Source

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Overview

• Introduction
• History of Instant Messaging
• The Jabber Protocol
• Client Application Design
• Demo

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Main Elements

• ltstream/gt, ltiq/gt, ltpresence/gt, and ltmessage/gt
• Common attributes
• to
• from
• type
• id
• To and from attributes use Jabber ID (JID)
• username_at_hostname/resource

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The ltstream/gt Element

• Client/Server sessions use the jabberclient
  namespace
• One session is two full XML documents
• ltstreamstream xmlnsstreamhttp//etherx.jabber.
  org/streams
• tojabber.org
• xmlnsjabberclientgt
•  
• other XML elements here
•  
• lt/streamstreamgt
• ltstreamerror/gt used for invalid XML

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The ltiq/gt Element

• IQ Info/Query
• Pairs of request/response elements
• get gt result
• set gt result
• Contain ltquery/gt subelement with namespace
• jabberiqagents
• jabberiqauth
• jabberiqregister
• jabberiqroster
• jabberiqversion

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ltiq/gt Examples

• Retrieve Roster
• Client ltiq typeget idgetRoster_0gt
• ltquery xmlnsjabberiqroster/gt
• lt/iqgt
•  
• Server ltiq typeresult idgetRoster_0gt
• ltquery xmlnsjabberiqrostergt
• ltitem jidpinkert_at_jabber.org
  subscriptionboth nameDr. Pinkertgt
• ltgroupgtCommitteelt/groupgt
• lt/itemgt
• ltitem jidamk_at_jabber.org
  subscriptionboth nameDr. Keunekegt
• ltgroupgtCommitteelt/groupgt
• lt/itemgt
• lt/querygt
• lt/iqgt

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ltiq/gt Examples Contd.

• Add to Roster
• Client ltiq typeset idsetRoster_0gt
• ltquery xmlnsjabberiqrostergt
• ltitem jidbrian_at_jabber.org nameBrian
  Tebbsgt
• ltgroupgtVaulterslt/groupgt
• lt/itemgt
• lt/querygt
• lt/iqgt
• Server ltiq typeresult idsetRoster_0
  fromnate_at_jabber.org tonate_at_jabber.org/
  gt

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The ltpresence/gt Element

• Used to send and receive entity availability
  information
• Types
• Available
• Unavailable
• Subscribe
• Unsubscribe
• Subscribed
• Unsubscribed

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The ltpresence/gt Element Contd.

• Available type subelements
• Show
• Status
• Priority
• X

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ltpresence/gt Examples

• Presence subscription
• Client ltpresence typesubscribe
  topinkert_at_jabber.org/gt
•  
• Server ltpresence typesubscribed
  frompinkert_at_jabber.org tonate_at_jabber
  .org/home/gt
• Setting presence
• Client ltpresence typeavailable
  fromnate_at_jabber.org/home
• topinkert_at_jabber.orggt
• ltshowgtchatlt/showgt
• ltstatusgtIm ready to chat!lt/statusgt
• ltprioritygt5lt/prioritygt
• ltx xmlnsjabberxdelay
  fromnate_at_jabber.org/home
• stamp20020424T110000/gt
• lt/presencegt

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The ltmessage/gt Element

• Used to send messages to other entities
• Message types
• Normal
• Chat
• Groupchat
• Headline
• Error

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ltmessage/gt Examples

• Normal Message
• ltmessage typenormal topinkert_at_jabber.orggt
• ltsubjectgtNew Chapterlt/subjectgt
• ltbodygt
• Ive finished another chapter. Please let me
  know what you think.
• lt/bodygt
• lt/messagegt
• Chat Message
• ltmessage typechat tonate_at_jabber.orggt
• ltthreadgt1234567890ABCDEF1234567890ABCDEFABlt/threa
  dgt
• ltbodygtWhen is your defense?lt/bodygt
• lt/messagegt

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Overview

• Introduction
• History of Instant Messaging
• The Jabber Protocol
• Client Application Design
• Demo

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XML Parser

• Streaming XML SAX
• Took suggestions from Brett McLaughlins Java
  XML
• Apache Xerces2 Java Parser was chosen

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Event-based Programming

• Messages are asynchronous
• Use callbacks to handle each message

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User Registration and Authentication

• Each Jabber server may require different
  Registration information
• There are three types of authentication
• Plain text
• SHA Digest
• Zero-knowledge

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Synchronization

• Multiple threads in the Jabber client
• Synchronization is done using the critical object
• synchronized(roster)
• // check if the user already exists in the
  roster
• if(getUserByJID(user.getJID()) ! null)
• roster.remove(user)
• roster.add(user)
• else
• roster.add(user)

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Overview

• Introduction
• History of Instant Messaging
• The Jabber Protocol
• Client Application Design
• Demo