text: #   Copyright 2014 Dan Krause
  #
  #   Licensed under the Apache License, Version 2.0 (the "License");
  #   you may not use this file except in compliance with the License.
  #   You may obtain a copy of the License at
  #
  #       http://www.apache.org/licenses/LICENSE-2.0
  #
  #   Unless required by applicable law or agreed to in writing, software
  #   distributed under the License is distributed on an "AS IS" BASIS,
  #   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  #   See the License for the specific language governing permissions and
  #   limitations under the License.
  
  import socket
  import http.client
  import io
  
  
  class SSDPResponse(object):
      class _FakeSocket(io.BytesIO):
          def makefile(self, *args, **kw):
              return self
  
      def __init__(self, response):
          r = http.client.HTTPResponse(self._FakeSocket(response))
          r.begin()
          self.location = r.getheader("location")
          self.usn = r.getheader("usn")
          self.st = r.getheader("st")
          self.cache = r.getheader("cache-control").split("=")[1]
  
      def __repr__(self):
          return "<SSDPResponse({location}, {st}, {usn})>".format(**self.__dict__)
  
  
  def discover(service, timeout=5, retries=1, mx=3):
      group = ("239.255.255.250", 1900)
      message = "\r\n".join([
          'M-SEARCH * HTTP/1.1',
          'HOST: {0}:{1}',
          'MAN: "ssdp:discover"',
          'ST: {st}', 'MX: {mx}', '', ''])
      socket.setdefaulttimeout(timeout)
      responses = {}
      for _ in range(retries):
          sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
          sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
          sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 2)
          message_bytes = message.format(*group, st=service, mx=mx).encode('utf-8')
          sock.sendto(message_bytes, group)
          while True:
              try:
                  response = SSDPResponse(sock.recv(1024))
                  responses[response.location] = response
              except socket.timeout:
                  break
          return list(responses.values())
  