ssdp.py

#   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 httplib
import StringIO
import struct

class SSDPResponse(object):
	class _FakeSocket(StringIO.StringIO):
		def makefile(self, *args, **kw):
			return self
	def __init__(self, response):
		self.orig_response = response
		if(response[0:13] == 'NOTIFY * HTTP'):
			response = response.replace("NOTIFY * HTTP/1.1","HTTP/1.1 200 OK")
		self.parsed_response = response
		r = httplib.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")
		if(self.cache):
			self.cache = self.cache.split("=")[1]
		self.nts = r.getheader("nts")
		if self.nts:
			self.st = r.getheader("nt")
	def __repr__(self):
		return "<SSDPResponse({location}, {st}, {usn}, {nts})>".format(**self.__dict__)

def discover(service, timeout=2, retries=1):
	group = ("239.255.255.250", 1900)
	message = "\r\n".join([
		'M-SEARCH * HTTP/1.1',
		'HOST: {0}:{1}',
		'MAN: "ssdp:discover"',
		'ST: {st}','MX: 3','',''])
	if(timeout):
		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)
		mreq = struct.pack('4sl', socket.inet_aton('239.255.255.250'), socket.INADDR_ANY) # pack MCAST_GRP correctly
		sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)         # Request MCAST_GRP
		#sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 2)
		sock.bind(('',1900))                           # Bind to all intfs
		sock.sendto(message.format(*group, st=service), group)
		while True:
			try:
				data = sock.recv(1024)
			except socket.timeout:
				break
			if(data):
				try:
					response = SSDPResponse(data)
					if response.location and (service == "ssdp:all" or service == response.st):
						yield response
				except:
					pass
# Example:
# import ssdp
# ssdp.discover("roku:ecp")

if __name__ == '__main__':
	for resp in discover("urn:schemas-upnp-org:device:MediaRenderer:1", 0):
		print resp