Programming Jabber

Reader cpfeifer contributes the review below of O'Reilly's Programming Jabber: if your job (or hobby) includes instant messaging in all its glory, Jabber is a free-beer, free-speech framework for setting up instant messaging systems not bound to a single server in the middle. As cpfeifer points out, instant messaging can mean a lot more than popping an on-screen note to your friend in Des Moines -- machines and programs can use a general purpose communication system like this, with no human middleman required. Programming Jabber author D.J. Adams pages 4555 publisher O'Reilly rating 9 reviewer http://cpfeifer.blogspot.com ISBN 0596002025 summary A detailed guide for developers to understanding and extending the Jabber messaging framework. Examples in Perl, Python and Java. The Scenario

Jabber was first conceived by Jeremie Miller (pic) in early 1998 in an effort to unify the disparate instant messaging networks. Instant Messaging networks rely on the network effect to gain and retain marketshare. The concept is the same when applied to any sort of participatory network whether it's a junk exchange, or content exchange, the value of the network increases with the square of the number of participants.

If this is true, then doesn't it follow that it is in the best interests of the IM networks to establish peering agreements with each other so that their users can directly contact users on other networks without having to install each client?

Hello, Jabber.

When I first picked up this book, I expected to understand the Jabber protocol in sufficient depth to implement my own IM client. Instead, the approach this book takes is that Jabber isn't just an XML-based protocol strictly for IM, rather it is a general purpose event notification protocol that has some very nice message routing and user management features built into it. While i was reading about the messages that Jabber has defined as part of the protocol, I could easily see other applications/devices generating Jabber messages to notify subscribers (either other systems, or people) of events.

Part 1 of the book focuses on getting you up to speed on the basics of Jabber technology: motivation, major features, XML protocol sample and compiling/configuring your own Jabber server. Chapter 2 presents the "10,000 foot view" of Jabber technology. In here you will find a sample client-query request/response flow with full HTTP headers, discussed step by step. The next two chapters are a very in-depth discussion of installing and configuring your own Jabber server. When you dive into a custom configuration of a fleet of Jabber servers (a "constellation" in Jabber terminology), it really starts to hit home that the real problem Jabber solves is far deeper than just IM.

From there, part 2 kicks off with a detailed discussion of the most basic building blocks of Jabber technology: resource identifiers, XML handling mechanism and the set of XML elements/attributes that make up the vocabulary of the Jabber protocol. Each element/attribute is presented with an annotated example and sample client/server interactions where appropriate. Examples can make or break a technical book, and these examples do a good job of illustrating how the element/attribute is used.

The following chapters take you through using standard Jabber features, user registration/authorization, messages, presence, groupchat, components and the event model to enable new applications. One very interesting application presented is enabling developers to receive CVS commit notifications via Jabber.

What's Bad?

I know the /. community is suspicious of glowing book reviews where everything is wonderful and nothing could be done to improve the book, so I'll nitpick. My major problem with this book is that the overwhelming majority of the sample applications are written in PERL/TK. This isn't a problem in and of itself, but I'm not a PERL/TK developer. If I build a Jabber solution, it will be in java, so PERL/TK samples don't do me a lot of good. I think equal time should be given to implementing Jabber using the two most-used languages, as defined by the number and activity of open source projects using Jabber technology.

What's Good?

This book covers everything relevant to Jabber technology, from lowest level inner workings and extensibility examples for developers to configuration and deployment for admins. Most of the book is spent looking directly at the Jabber XML protocol, instead of a specific API implementation. This way, the book covers the technology and doesn't get lost in how one particular API models the protocol.

So What's In It For Me?

If you want to implement an inside-the-firewall IM solution for your company/group/tribe or investigate integrating event notification into an application, this is a great starting point. If you're just curious about Jabber and want to know how it works, then this will give you enough information to get you hooked.

Table of Contents

PART 1: Getting Started with Jabber

• Chapter 1. Introducing Jabber
• Chapter 2. Inside Jabber
• Chapter 3. Installing the Jabber Server
• Chapter 4. Server Architecture and Configuration

PART 2: Putting Jabber's Concepts to Work

• Chapter 5. Jabber Technology Basics
• Chapter 6. Jabber Namespaces
• Chapter 7. User Registration and Authorization
• Chapter 8. Using Messages and Presence
• Chapter 9. Groupchat, Components, and Event Models
• Chapter 10. Pointers for Further Development

Appendix A. The Jabber.xml Contents

Appendix B. The IQRPC Classes for JabberRPCResponder

Index

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Comments

Jabber is a hack

[ProfessorPuke]

As are all "Instant Message" programs. They are a poorly-designed, short-sighted solution to a problem that should've been addressed elsewhere in the internet architecture.

Part of the problem stems from the fact that IM software addresses 2 applications at the same time, unnecessarily coupling the implementations. These problems could really be approached separately:

• Learn the IP address associated with a globally-unique username
• Send a text message to the interactive operator of a machine with an IP address

The first problem is the much more interesting one- Jabber & AIM already somewhat solve it, but in an unsatisfactory and poorly extensible way. Better solutions would be based on an extension to the normal DNS system- essentially, you want each human to have a resolvable domain name associated with her. With that in place, InstantMessaging is an easy problem.

A person could try to implement "TCP over IM", but it would've been nicer if the systems had been designed for this from the start. Actually, there is a 3rd general-purpose facility that might be needed, for reasons of privacy. There should be a way to send a packet to a "resolvable human name", without knowing the IP address it currently maps through. The (trusted) central server will have to forward packets in both directions. (I think that's how AIM normally operates, except that it doesn't accept generic packets, only AIM-formatted messages).

However, that method doesn't uniformly improve privacy. While it does prevent other users from learning your IP address, it makes it much easier for AOL (or other central server operator) to spy on the contents of your discussions. (You should be using encryption, anyway).

Jabber shortcomings - not in the book

[mgkimsal2]

The book, from what I read of it (not 100% - maybe 60%) is handy, but didn't tell me much beyond the jabber documentation already out there.

What seems to be a huge issue for Jabber is user profile integration with databases. There seems to be an unsupported mysql hack, but the key is 'unsupported'. If you look in the Jabber mail list archives, every month there's people asking how to do it, but NEVER any answers.

Another great one that doesn't get answered - which the book doesn't address either - is the format of the user XML files. Each user by default has an XML file, and many people would like to create them programatically. There is no definitive resource which explains what's in a file and what isn't, and how to put one together. I've hacked something, and it works, but only after several attemps, and it doesn't *feel* good. I'm hesitant to try to add anything else lest I break what's working.

Jabber.com has a huge vested interest in keeping some of this stuff not in the public knowledgebase, because they charge (comparitively) a LOT of money for their stuff.

Last time I spoke with them the minimum to get started was $16,000. Their package offers a completely rewritten jabber server (better thread handling), Oracle and LDAP connectors, and a good Java applet client.

NO ONE in the open source community has even come close to having a Java applet client that is workable in a practical sense.

So yes, the protocol is open, and free, but there doesn't seem to be much consensus on tools, except from Jabber.com and they cost.

What I think Jabber as an open source project needs to focus on:

* XML user file definition and/or database support for user profiles
* Good applet client

:)

wrong

[Milkman Ken]

You can very easily cluster jabber servers. In fact, I have five running:

one for the main server

one specifically for AIM

one for ICQ

one for MSN

one for yahoo! IM

the four IM trasport servers have their own jabberd process. If a transport server dies (as they occasionally do), you can bring that server back up without affecting any other servers.

But you don't have to break up the servers this way. You could run multiple jabber servers, and place bandwidth restrictions on them so that when a jabber server got "full", it would stop receiving connections, so the jabber server above it in the chain would then forward it on to the next jabber server in the chain, or back up if it's out of children servers.

it's a relatively simple matter to setup an init.d script to monitor the health of all the processes, and restart them when and if they fail. I've been running a jabber server on one of our linux boxes for weeks now, and I haven't had to touch it once. I highly recommend jabber for intranets.

Java Oriented Jabber Book

[Temas]

I've seen a lot of comments disliking the abundance of Perl/Tk usage in DJ's book. Recently Manning Publications released Instant Messaging in JAVA: The Jabber Protocols in print and ebook. It was written by Iain Shigeoka, and is ISBN 1-930110-46-4. It's a good read and goes over the creation of both a client and a basic server in Java, plus a good deal more.