worker.rb

require 'eventmachine'
require 'fiber'

Q = Array.new

worker = Fiber.new do
  loop do
    Fiber.yield
    blk = Q.shift
    blk.call if blk
  end
end

module QueuedEchoServer
  def receive_data(data)
    Q << lambda { send_data(data.chomp + ': ' + Time.now.to_s + "[#{Q.size}]\n") }
    send_data "added input to the queue...\n"
  end
end

EM.run do
  host = '0.0.0.0'
  port = 8080
  EM.start_server host, port, QueuedEchoServer
  puts "Started QueuedEchoServer on #{host}:#{port}..."

  EM.add_periodic_timer(5) do
    worker.resume
  end
end