em_websocket.rb

require 'em-websocket'

EM.run do
  channel = EM::Channel.new
  options = {:host => "0.0.0.0", :port => 8080}

  EM::WebSocket.start(options) do |ws|
    ws.onopen do
      sid = channel.subscribe{|msg| ws.send msg}
    end

    ws.onclose do
      channel.unsubscribe(sid)
    end
  end
end