EM HttpServer written by Moi.rb

require 'rubygems'
require 'eventmachine'
require 'evma_httpserver'
require 'uri'


class Static < EM::Connection
  include EM::HttpServer

  def post_init
    super
    no_environment_strings
  end

  def process_http_request
    @header_processing = false
    filename = Dir.pwd + URI.parse(@http_request_uri).path
    response = EM::DelegatedHttpResponse.new(self)

    if File.exists?(filename)
      response.status = 200
      response.content = File.readlines(filename,'b')
      response.send_response
    else
      response.status = 404
      response.content = "404 Error\n"
      response.send_response
    end
  end
end

EM.run {
  EM.epoll
  EM.start_server '0.0.0.0', 8081, Static
}

One thing that differs between this and your node version is the fact that File.readlines is synchronous where fs.readFile is not. It looks like EventMachine doesn't have a straight-forward asynchronous way to read files but it might be worth trying EventMachine::FileStreamer.