blocking.rb

require 'celluloid/io'
require 'http'

class Client
  include Celluloid::IO
  def transmit
    HTTP.get('http://127.0.0.1:1337', socket_class: Celluloid::IO::TCPSocket)
  end
end

pool = Client.pool
10.times.map{ pool.future.transmit }.map(&:value)

non_blocking.rb

require 'celluloid/io'
require 'http'

class Client
  include Celluloid::IO
  def transmit
    HTTP.get('http://127.0.0.1:1337', socket_class: Celluloid::IO::TCPSocket)
  end
end

client = Client.new
10.times.map{ client.future.transmit }.map(&:value)

server.js

var http = require('http');
var count = 0;

http.createServer(function (req, res) {
  count = count + 1;
  console.log('Parallel client opens connection ' + count);
  
  req.connection.on('close',function(){
    count = count - 1;
    console.log('Parallel client closes connection ' + count);
  });

  setTimeout(function(){
    res.writeHead(200, {'Content-Type': 'application/json'});
    res.end('{"foo":"boo"}');
  }, 2000);
  
}).listen(1337, '127.0.0.1');

console.log('Server running at http://127.0.0.1:1337/');