application.rb

require 'action_controller/railtie'

module Myapp
  class Application < Rails::Application
    config.secret_token = 'd38ad04f101b78570a76ecd1d4664e2b'

    routes.append do
      get '/' => 'myapp/hello#world'
    end
  end

  class HelloController < ActionController::Base
    def world
      render :text => 'Hello World!'
    end
  end
end

Myapp::Application.initialize!
Rack::Handler::WEBrick.run Myapp::Application, :Port => 3000