Network I/O ruby Event handling chat server

gistfile1.rb

#event loop demystified ruby
#Working with network I/O in Ruby is so easy:
#https://practicingruby.com/articles/event-loops-demystified
require 'socket'

# Start a server on port 9234
server = TCPServer.new('0.0.0.0', 9234)

# Wait for incoming connections
while io = server.accept
  io << "HTTP/1.1 200 OK\r\n\r\nHello world!"
  io.close
end

#chat server
class ChatServer
  def initialize
    @clients = []
    @client_id = 0
  end

  def <<(server)
    server.on(:accept) do |stream|
      add_client(stream)
    end
  end

  def add_client(stream)
    id = (@client_id += 1)
    send("User ##{id} joined\n")

    stream.on(:data) do |chunk|
      send("User ##{id} said: #{chunk}")
    end

    stream.on(:close) do
      @clients.delete(stream)
      send("User ##{id} left")
    end

    @clients << stream
  end

  def send(msg)
    @clients.each do |stream|
      stream << msg
    end
  end
end

# usage

io     = IOLoop.new
server = ChatServer.new

server << io.listen('0.0.0.0', 1234)

io.start

#Test Script
# from User #1's console:
$ telnet 127.0.0.1 1234

User #2 joined
User #2 said: Hi
Hi
User #1 said: Hi
User #2 said: Bye
User #2 left

# from User #2's console (quits after saying Bye)
$ telnet 127.0.0.1 1234

User #1 said: Hi
Bye
User #2 said: Bye

#Event Handling 
module EventEmitter
  def _callbacks
    @_callbacks ||= Hash.new { |h, k| h[k] = [] }
  end

  def on(type, &blk)
    _callbacks[type] << blk
    self
  end

  def emit(type, *args)
    _callbacks[type].each do |blk|
      blk.call(*args)
    end
  end
end

class HTTPServer
  include EventEmitter
end

server = HTTPServer.new
server.on(:request) do |req, res|
  res.respond(200, 'Content-Type' => 'text/html')
  res << "Hello world!"
  res.close
end

# When a new request comes in, the server will run:
#   server.emit(:request, req, res)