#!/usr/bin/env ruby require "eventmachine" module ErrorServer def receive_data(data) case data when %r{^GET /error/not_found\s} send_data "HTTP/1.1 404 Not Found\r\n" send_data "\r\n" send_data "server says not found" close_connection(true) end end end EM.run do EM.start_server("127.0.0.1", 9292, ErrorServer) $stderr.puts "ready" end