Ruby/Cramp/Eventmachine implementation of Status: abandonware
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NOTICE This project is no longer maintained. I will accept tested pull requests, but that's it!

[] for the Ruby Kids. A plugin for Cramp. is a library that makes writing cross-borwser websockets super easy and resilient.


This implementation works within an existing cramp app. Cramp is similar in spirit to Rails but specializes in evented web apps. Simply gem install cramp and run cramp new myapp.

Define a new Cramp::Action and include SocketIo::Websocket. Then define which method should handle certain events and messages.

# app/actions/akbar_action.rb

class AkbarAction < Cramp::Websocket
  include SocketIo::Websocket

  on :message, :read_message
  on :trap, :report_trap
  # This is fired when the client sends a standard 
  # message
  def read_message(data)
    puts "Our Bothan spies report #{data}"
  def report_trap(imperial_fleet)
    puts "It's a trap!"
    puts "Concentrate all firepower on #{imperial_fleet['super_stardestroyer']}"
    return { 'move' => 'sector 227' }

By default, Cramp uses HttpRouter in config/routes.rb to manage connections. SocketIo has a handy helper for that:

# config/routes.rb

require ''
require 'http_router' do
  SocketIo.routes self, AkbarAction

Optionally, SocketIo.routes can take a path. The default is /

Throw that in with some Thin or Rainbows, and you've got yourself a websocket server!

Note that you'll need to configure cramp's websocket adapter to use thin or rainbows:


Cramp::Websocket.backend = :rainbows  # or :thin

Here's the client-side code to make it all happen:

<script type="text/javascript" src=""></script>
<script type="text/javascript">
  var socket = io.connect('http://localhost/');
  socket.on('connect', function () {
    socket.send('the Emperor is building a new Death Star');
    socket.emit('trap', { 'super_stardestroyer': 'Executor' }, function(instructions) {
      alert('moving to ' + instructions['move']);

Note on Patches/Pull Requests

  • Fork the project.
  • Make your feature addition or bug fix.
  • Add tests for it. This is important so I don't break it in a future version unintentionally.
  • Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
  • Send me a pull request. Bonus points for topic branches.


Copyright (c) 2011 Derek Kastner. See LICENSE for details.