client.rb

require 'rubygems'
require 'eventmachine'

module TapsClient
  def connection_completed
    p [Time.now, :connected]
    send_data("hey!")
  end

  def receive_data(data)
    p [Time.now, :data, data]
    STDOUT.flush
  end

  def unbind
    p [Time.now, :disconnected]
  end
end

EventMachine.run do
  EM.connect 'localhost', 5678, TapsClient
end

server.rb

require 'rubygems'
require 'eventmachine'

module TapsServer
  def post_init
    p [Time.now, :connected]
  end

  def recieve_data(data)
    p [Time.now, :data, data]
    send_data(data)
  end

  def unbind
    p [Time.now, :disconnected]
  end
end

EM.run do
  EM.start_server 'localhost', 5678, TapsServer
end