AppleTV の IP アドレスを検出する。LAN 内に複数 AppleTV ある時の動作はわかりません。OSX 10.8 & Emacs 24.2 、及び Ubuntu 12.04 & Emacs 23.2 で動作確認 http://gongo.hatenablog.com/entry/2013/01/17/004306

find-appletv.el

(require 'dns)

(with-temp-buffer
  (let ((process (make-network-process :name "mdns"
                                       :coding 'binary
                                       :buffer (current-buffer)
                                       :host "224.0.0.251"
                                       :service 5353
                                       :type 'datagram))
        (send-text (dns-write
                    `((id ,(random 65000))
                      (opcode query)
                      (queries (("_airplay._tcp.local" (type PTR)))))))
        response ip)
    (process-send-string process send-text)
    (when (zerop (buffer-size))
      (accept-process-output process 5)) ;; wait 5sec
    (setq response (buffer-string))
    (delete-process process)
    (if (zerop (length response)) nil
      (dns-get 'data (car (dns-get 'additionals (dns-read response)))))))