Posts Tagged ‘Chatterl’


Changes in Chatterl

July 23, 2009

I haven’t worked on Chatterl for a few months but there are some fundemental changes that had been made back in March, apologies for the slow update but honestly I haven’t had much time with learning Rails & freelance work.


Well the main changes in chatterl are the following:

  • Message storage
  • Registration
  • Introduction of unit tests
  • API calls

I’ll go over each section, highlighting the main changes & who it affects Chatterl as a whole.


After implementing Chatterl‘s basic functionality (see chatterl post). The next step was to create to implement CWIGA, Chatterl Web Interface Gateway API. With this new module Chatterl is able to be interacted with purely via HTTP. The first implementation was rough, the original source can be found here, though it allowed me to get a decent understanding of mochiweb at the time helped me produce this article. After implementing unit tests to cover the project as a whole I felt comfortable to make a few fundamental changes to CWIGA’s API and requests to Chatterl.


I’ve added very basic registration functionality to Chatterl, allowing users to register to the system, giving them the ability to retrieve archived messages & later creation of their own chat groups. In hindsight I’d like to move this functionality to the front-end (which I’ll more than likely be in Rails).

Message Storage

Again this was more experimental on my part and something I would like to move over to couchDB when I get the chance, for the moment, Chatterluses mnesia to store users messages when they are not logged into the system.

Added test cases

One of the main issues I’ve been having with Sinan more than anything else, was seperating my tests from the source code. I really hated the idea of having test & implementation code mixed in, so I stayed away from any kind of real testing until I got my head around it. Thanks to Kev Smith‘s own code, I finally got my head around EUnit, which I posted a short post on here.

Before I was comfortable with implementing any more functionality I had set out to cover as much of Chatterl‘s code as possible. In doing so I uncovered a number of silly little bugs (oversights) in the coding logics & made the necessary changes.

General cleanup

The way chatterl is called has also been improved, instead of having to go into erl you can simple run ./ within the cd _build/development/apps/chatterl- directory. This will start up all the processes need to use chatterl.

CWIGA is setup to listen on port 9000, so you can call it using curl or via a browser of your choice. It accepts XML & JSON requests & has been made more RESTful.

Hopefully in the near future I’ll have time to rewrite the code base and improve on the basic functionality but for the meantime I hope this helps others as much as its been an experience for me.


Chatterl – Erlang based chat engine

January 1, 2009

Well I’ve been hacking around for the past few months trying to get my head around Erlang. After playing around with Twitterl I decided I should start a new project (OTP based) which I have a decent understanding of & have wanted to work on for some time. A chat system was the first thing that came to mind, I’ve worked on and built a few in my time and thought Erlang would be a good language to build a chat engine from scratch.

For those not interested in the long description and prefer to dive in source, you can find a copy of the project at github.


A chat system that can be housed over a number of nodes and track clients over varying devices, at the time of the writing the system works over multiple nodes and is able to do the basics (connect to a group, send message to other clients and connected groups).

The main focus of this project is to create a chat system that is highly reliable as well as scaleable. Other developers will be able to create add-on modules that are able to interact with chatterl and further enhance the functionality of chatterl and the chatterl clients experience.

As mentioned the system is OTP based, of which it uses Sinan to maintain its builds.

Installing Chatterl

At the moment of this writing Chatterl is still in alpha so their is no real release at the moment, to get it running you will need to do the following:

git-clone git:// &&
cd chatterl &&
sinan doc && 
sinan dist &&
cd _/build/development/tar &&
sudo faxien install-release chatterl-

The above presumes that you have Sinan configured & installed, if you haven’t refer to erlware.
You will need to change to cookie & name values to something else, doing so should drop you into the erlang shell & ready to run the Chatterl application. To run a client on a different machine you will need to do the above if (making sure that the -sname is not the same as any other connected nodes & that the cookie is the same) if connecting on the same box simply cd to the ebin directory and run the following command:

erl -name bar -setcookie abc

From here you will need to make sure that they nodes can connect via:


Where foo is the node name & is the tld of the node box (indicated within yout hosts file or dns server).
Once you receive the infamous pong response you are ready to roll.


  • Client login/logout to Chatterl.
  • List Chatterl groups.
  • List Chatterl users.
  • Login/logout of a chatterl group.
  • Send message to a group and other clients.

Future Features

  • Centralised Error logging and data storage.
  • Client customisable routines (able to poll RSS feeds, twitter, FB and the such like).
  • Better handling of errors.
  • User registration.
  • FB Connect.
  • Chat bots (AIML based).
  • Web interface/API.
  • Chat modules handler(banning, censorship, chatbots).


Starting the server
Chatterl server runs as an OTP application and uses a supervisor to manage it (in later versions there will be options to spawn multiple servers, allowing for a more fault tolerant chat system). To start up the server you simply need to run the following command:


Which will initialise the server allowing clients to connect and groups to be created. Groups can be created on differing nodes as long as the node can communicate with the chatterl_serv.

Starting a group
Chatterl groups can be started on any node that can communicate with the server, this allows the user to create a number of groups on varying nodes, helping with general organisation as well a performance and reliablity.

A group can be initialised by calling the command:


which will spawn a group process which users can connect to.

Connection to chatterl
At the time of this writing chatterl_clients can only spawn a client per node, this will later be changed once the web interface has been fully implemented, possibly to a refactoring the client to a parameterised module.
For the moment node users must follow the basic OTP configurations (same cookie, valid DNS name, etc). Creating a connection to the server is done by using the following command.


This will initialise a user and connect them to chatterl_serv (must be done before users can join a group or communicate with other chatterl users).

Disconnecting from chatterl
Chatterl clients can simply disconnect from chatterl by issuing the following command:


This will disconnect the user from all the groups they are currently connected to as well as the actual Chatterl server.

Joining a group
This can be done by using the following command:


If the group exists the user is able to join the group allowing them to send message to the room.

Dropping from a group
This is as simple as connection, simply supply the following command:


This will send a message to the group, which will handle the termination.

Sending group message


GroupName being the name of the group the client is connected to, Message being the message that you want to send to the receiving client. If the message is sent successfully all users connected to the group will receive the message.

Sending a private message
This allows a Chatterl client to send a private message to another client, by executing the following:


If the message is sent successfully then the sender will receive follow message:


in turn sending the message to the receipients node.