Any success with Sinatra working together with EventMachine WebSockets?

ruby sinatra websocket rack eventmachine

15,959

Solution 1

Did not try it, but should not be too hard:

require 'em-websocket'
require 'sinatra/base'
require 'thin'

EM.run do
  class App < Sinatra::Base
    # Sinatra code here
  end

  EM::WebSocket.start(:host => '0.0.0.0', :port => 3001) do
    # Websocket code here
  end

  # You could also use Rainbows! instead of Thin.
  # Any EM based Rack handler should do.
  Thin::Server.start App, '0.0.0.0', 3000
end

Also, Cramp has a websocket implementation that works directly with Thin/Rainbows! you might be able to extract, so you won't even need to run the server on another port.

Solution 2

Thanks Konstantin... that worked! I had to tweak your code slightly. I added comments where I changed it.

-poul

require 'rubygems'      # <-- Added this require
require 'em-websocket'
require 'sinatra/base'
require 'thin'

EventMachine.run do     # <-- Changed EM to EventMachine
  class App < Sinatra::Base
      get '/' do
          return "foo"
      end
  end

  EventMachine::WebSocket.start(:host => '0.0.0.0', :port => 8080) do |ws| # <-- Added |ws|
      # Websocket code here
      ws.onopen {
          ws.send "connected!!!!"
      }

      ws.onmessage { |msg|
          puts "got message #{msg}"
      }

      ws.onclose   {
          ws.send "WebSocket closed"
      }

  end

  # You could also use Rainbows! instead of Thin.
  # Any EM based Rack handler should do.
  App.run!({:port => 3000})    # <-- Changed this line from Thin.start to App.run!
end

Solution 3

I stumbled onto this websocket-rack github project which is basically a rackified em-websocket and actually got it to work nicely side-by-side with a Sinatra app. Here's my config.ru:

require 'rubygems'
require 'rack/websocket'
require 'sinatra/base'

class WebSocketApp < Rack::WebSocket::Application
  # ...
end

class SinatraApp < Sinatra::Base
  # ...
end

map '/ws' do
  run WebSocketApp.new
end

map '/' do
  run SinatraApp
end

Have fun!
Colin

Solution 4

I've been using sinatra-websocket. It let's you run the websocket server in the same process and on the same port as Sinatra.

Disclaimer: I'm the maintainer.

require 'sinatra'
require 'sinatra-websocket'

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

get '/' do
  if !request.websocket?
    erb :index
  else
    request.websocket do |ws|
      ws.onopen do
        ws.send("Hello World!")
        settings.sockets << ws
      end
      ws.onmessage do |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
end

__END__
@@ index
<html>
  <body>
     <h1>Simple Echo & Chat Server</h1>
     <form id="form">
       <input type="text" id="input" value="send a message"></input>
     </form>
     <div id="msgs"></div>
  </body>

  <script type="text/javascript">
    window.onload = function(){
      (function(){
        var show = function(el){
          return function(msg){ el.innerHTML = msg + '<br />' + el.innerHTML; }
        }(document.getElementById('msgs'));

        var ws       = new WebSocket('ws://' + window.location.host + window.location.pathname);
        ws.onopen    = function()  { show('websocket opened'); };
        ws.onclose   = function()  { show('websocket closed'); }
        ws.onmessage = function(m) { show('websocket message: ' +  m.data); };

        var sender = function(f){
          var input     = document.getElementById('input');
          input.onclick = function(){ input.value = "" };
          f.onsubmit    = function(){
            ws.send(input.value);
            input.value = "send a message";
            return false;
          }
        }(document.getElementById('form'));
      })();
    }
  </script>
</html>

Solution 5

FYI, you can also use Padrino apps with EventMachine (as they are subsets of Sinatra apps):

require 'rubygems'
require 'eventmachine'
require 'padrino-core'
require 'thin'
require ::File.dirname(__FILE__) + '/config/boot.rb'

EM.run do
  Thin::Server.start Padrino.application, '0.0.0.0', 3000
end

Cheers, Mike

View more solutions

15,959

Author by

Poul

Chief Technology Officer at Athena Capital Research

Updated on June 27, 2022

Comments

Poul almost 2 years

I have been using Sinatra for sometime now and I would like to add some realtime features to my web-app by pushing the data via websockets.

I have successfully used the gem 'em-websocket' on its own, but have not been able to write one ruby file that has a sinatra web server AND a web-socket server.

I've tried spinning the run! or start! methods off in separate threads with no success.

Has anyone gotten this to work?

I want to have them in the same file as I can then share variables between the two servers.

Thanks!
Redoman over 11 years

..being this the quickest way to use websocket with sinatra (to my eyes), can I ask which disadvantages this approach brings compared to using 'em-websocket', subclassing Sinatra::Base, and "manually" plugging into the event loop ?
Redoman over 11 years

also could anyone give a short explaination on why is "next_tick" needed here?
Sunder over 11 years

@@simulacre -- Any ideas how to make this work on a load balanced setup? I mean from the example above, every Sinatra process would then have its own "settings.sockets" array turning the process stateful?
Dave Sag about 11 years

This works well. One question though, how can the EventMachine socket events access the session info to authenticate that events are comming from a properly authenticated user?
Dave Sag about 11 years

That's is pretty much how I've done it. I have a related question however which is how do I decode the Rack::Server::Cookie (set in the Sinatra class) value returned in the handshake passed by the client to ws.onopen. See my question in more detail at stackoverflow.com/questions/16312024/…
Dave Sag about 11 years

I've outlined this as per my comment on @Konstanti Haase's answer, as a new question - see stackoverflow.com/questions/16312024/…
Alex Martín Jiménez over 10 years

He literally says "Here's my config.ru:". So I think "Yes" is the answer :)
Guillaume Roderick about 8 years

Absolutely lovely :)