I could not really find an easy example how to get started with Jabber components (using xmpp4r), so this I will cover the absolute basics here.

You will need a Jabber server to connect your component to. I suggest to install ejabberd locally. Also needed is xmpp4r, which can be installed through rubygems (e.g. using sudo gem install xmpp4r). Feel free to use your favourite package manager to install it, if packaged.

The following snippet is used to configure ejabberd to listen for your component. After altering the configuration, do not forget to restart ejabberd. DNS seems to be important for elang-stuff, so make sure the host you use (e.g. localhost) can be resolved properly.

 {5348, ejabberd_service, [
                            {access, all}, 
                            {shaper_rule, fast},
                            {ip, {127, 0, 0, 1}},
                            {host, "mycomponent.localhost",
                             [{password, "secret"}]
                            }
                           ]},

Take a look at the sample configfile and use a predefined, commented service configuration, so you won’t have to fiddle with erlang-stuff.

Now you can create this small file, name it mycomponent.rb and use the following content:

require 'xmpp4r'

class MyComponent < Jabber::Component
	def initialize config
		super config['jid']
		
		# connect to the main server
		connect config['server'], config['port']
		
		# authenticate
		auth config['password']
		
		add_message_callback do |message|
			Thread.new do
				handle_message message
			end
		end
		
		# stop this thread
		Thread.stop
	end
	
	# handles incoming messages
	def handle_message message
		puts "received message from #{message.from}: #{message.body}"
	end
end

# configuration
config = {
	'jid' => 'mycomponent.localhost',
	'server' => 'localhost',
	'port' => 5348,
	'password' => 'secret'
}

# instantiate, connect and auth
mycomponent = MyComponent.new config

Using this kind of Hash as configuration makes it very easy to use YAML to store your configuration in a file. If ruby can’t find xmpp4r, you might have to require 'rubygems' before, if you installed xmpp4r via rubygems.

Now you can run your component and send messages to mycomponent.localhost. The handle_message will print any messages received.

Sometimes you might want a Singleton Logger in Ruby. Here is what works:

require 'logger'
require 'singleton'

class Logger
    include Singleton
    @@old_initialize = Logger.instance_method :initialize

    def initialize
        @@old_initialize.bind(self).call(STDERR)
    end  
end

I have put some glue between xmpp4r and twitter, et voila, a Jabber component mapping
microblogging to a Jabber Multi-User-Chat.

Working right now:

• friends joining as participants


• friends timeline


• posting updates


• sending and receiving direct/private messages

Missing:

• follow/unfollow (I'd like to implement this as invite/kick)


• blocking (ban)


• avatars (can be easily done)


• a lot more

You can try this out by joining the MUC-room {identi.ca|twitter}@omb.jabber.teamidiot.de
and using your username as nickname and providing your password.
As this is not safe (I might steal your password) I suggest to setup your own component,
try it out and provide feedback.

The repository (mercurial) is at: http://gonzo.teamidiot.de/repos/ombmuc/.