A WEBrick shell server with async output

shell_server.rb

require 'webrick'

class Server < WEBrick::HTTPServlet::AbstractServlet

  def self.start(port,host=nil)
    server = WEBrick::HTTPServer.new(:Host => host, :Port => port)
    server.mount '/', self

    trap('INT') { server.shutdown }

    server.start
  end

  def self.shell
    @@shell ||= begin
                  io = IO.popen(ENV['SHELL'],'r+')
                  io.extend AsyncRead
                  io
                end
  end

  def do_POST(request,response)
    self.class.shell.puts request.query['cmd']

    response.status = 200
  end

  def do_GET(request,response)
    response.status  = 200
    response.chunked = true
    response.body    = self.class.shell
  end

  module AsyncRead

    def read(length)
      begin
        read_nonblock(length)
      rescue IO::WaitReadable
        IO.select([self])
        retry
      end
    end

  end

end

Server.start 1337