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


class SSDPResponse(object):
    class _FakeSocket(StringIO.StringIO):
        def makefile(self, *args, **kw):
            return self

    def __init__(self, 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").split("=")[1]

    def __repr__(self):
        return "<SSDPResponse({location}, {st}, {usn})>".format(**self.__dict__)


def discover(service, timeout=10, retries=1, limit=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',
        '',
        '',
    ])
    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)
        sock.sendto(message.format(*group, st=service), group)

        while True:
            if len(responses) >= limit:
                break

            try:
                response = SSDPResponse(sock.recv(1024))
                responses[response.location] = response
            except socket.timeout:
                break

    return responses.values()