Gemfile

source 'https://gems.ruby-china.org'

gem 'sinatra'
gem 'sinatra-websocket'

web-socket.rb

require 'sinatra'
require 'sinatra-websocket'

set :server, 'thin'
set :sockets, []

get '/ws' do
  request.websocket do |ws|
    ws.onopen do
      ws.send("connected")
      settings.sockets << ws
    end
    ws.onmessage do |msg|
      p msg
      EM.next_tick { settings.sockets.each{|s| s.send(msg) } }
    end
    ws.onclose do
      warn("websocket closed")
      settings.sockets.delete(ws)
    end
  end
end