let echo ic oc =
    let char_stream = ref None in
    let t = Lwt_timeout.create 10 begin fun () ->
        (match !char_stream with
         | None -> log_info_bad "this is bad"
         | Some c ->
           Lwt_io.write_chars oc c)
        |> Lwt.ignore_result
      end
    in
    Lwt_timeout.start t;
    Lwt.return (char_stream := Some (Lwt_io.read_chars ic))