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290 lines
8.5 KiB
290 lines
8.5 KiB
"""Module that implements SSDP protocol."""
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import re
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import select
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import socket
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import logging
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from datetime import datetime, timedelta
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from xml.etree import ElementTree
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import requests
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import zeroconf
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from netdisco.util import etree_to_dict
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DISCOVER_TIMEOUT = 2
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# MX is a suggested random wait time for a device to reply, so should be
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# bound by our discovery timeout.
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SSDP_MX = DISCOVER_TIMEOUT
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SSDP_TARGET = ("239.255.255.250", 1900)
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RESPONSE_REGEX = re.compile(r'\n(.*?)\: *(.*)\r')
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MIN_TIME_BETWEEN_SCANS = timedelta(seconds=59)
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# Devices and services
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ST_ALL = "ssdp:all"
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# Devices only, some devices will only respond to this query
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ST_ROOTDEVICE = "upnp:rootdevice"
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class SSDP:
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"""Control the scanning of uPnP devices and services and caches output."""
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def __init__(self):
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"""Initialize the discovery."""
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self.entries = []
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self.last_scan = None
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def scan(self):
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"""Scan the network."""
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self.update()
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def all(self):
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"""Return all found entries.
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Will scan for entries if not scanned recently.
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"""
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self.update()
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return list(self.entries)
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# pylint: disable=invalid-name
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def find_by_st(self, st):
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"""Return a list of entries that match the ST."""
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self.update()
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return [entry for entry in self.entries
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if entry.st == st]
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def find_by_device_description(self, values):
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"""Return a list of entries that match the description.
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Pass in a dict with values to match against the device tag in the
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description.
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"""
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self.update()
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seen = set()
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results = []
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# Make unique based on the location since we don't care about ST here
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for entry in self.entries:
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location = entry.location
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if location not in seen and entry.match_device_description(values):
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results.append(entry)
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seen.add(location)
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return results
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def update(self, force_update=False):
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"""Scan for new uPnP devices and services."""
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if self.last_scan is None or force_update or \
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datetime.now()-self.last_scan > MIN_TIME_BETWEEN_SCANS:
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self.remove_expired()
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self.entries.extend(
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entry for entry in scan()
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if entry not in self.entries)
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self.last_scan = datetime.now()
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def remove_expired(self):
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"""Filter out expired entries."""
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self.entries = [entry for entry in self.entries
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if not entry.is_expired]
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class UPNPEntry:
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"""Found uPnP entry."""
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DESCRIPTION_CACHE = {'_NO_LOCATION': {}}
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def __init__(self, values):
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"""Initialize the discovery."""
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self.values = values
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self.created = datetime.now()
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if 'cache-control' in self.values:
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cache_directive = self.values['cache-control']
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max_age = re.findall(r'max-age *= *\d+', cache_directive)
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if max_age:
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cache_seconds = int(max_age[0].split('=')[1])
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self.expires = self.created + timedelta(seconds=cache_seconds)
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else:
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self.expires = None
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else:
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self.expires = None
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@property
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def is_expired(self):
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"""Return if the entry is expired or not."""
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return self.expires is not None and datetime.now() > self.expires
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# pylint: disable=invalid-name
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@property
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def st(self):
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"""Return ST value."""
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return self.values.get('st')
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@property
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def location(self):
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"""Return Location value."""
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return self.values.get('location')
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@property
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def description(self):
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"""Return the description from the uPnP entry."""
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url = self.values.get('location', '_NO_LOCATION')
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if url not in UPNPEntry.DESCRIPTION_CACHE:
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try:
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xml = requests.get(url, timeout=5).text
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if not xml:
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# Samsung Smart TV sometimes returns an empty document the
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# first time. Retry once.
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xml = requests.get(url, timeout=5).text
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tree = ElementTree.fromstring(xml)
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UPNPEntry.DESCRIPTION_CACHE[url] = \
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etree_to_dict(tree).get('root', {})
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except requests.RequestException:
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logging.getLogger(__name__).debug(
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"Error fetching description at %s", url)
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UPNPEntry.DESCRIPTION_CACHE[url] = {}
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except ElementTree.ParseError:
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logging.getLogger(__name__).debug(
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"Found malformed XML at %s: %s", url, xml)
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UPNPEntry.DESCRIPTION_CACHE[url] = {}
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return UPNPEntry.DESCRIPTION_CACHE[url]
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def match_device_description(self, values):
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"""Fetch description and matches against it.
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Values should only contain lowercase keys.
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"""
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device = self.description.get('device')
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if device is None:
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return False
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return all(device.get(key) in val
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if isinstance(val, list)
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else val == device.get(key)
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for key, val in values.items())
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@classmethod
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def from_response(cls, response):
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"""Create a uPnP entry from a response."""
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return UPNPEntry({key.lower(): item for key, item
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in RESPONSE_REGEX.findall(response)})
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def __eq__(self, other):
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"""Return the comparison."""
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return (self.__class__ == other.__class__ and
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self.values == other.values)
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def __repr__(self):
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"""Return the entry."""
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return "<UPNPEntry {} - {}>".format(self.location or '', self.st or '')
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def ssdp_request(ssdp_st, ssdp_mx=SSDP_MX):
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"""Return request bytes for given st and mx."""
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return "\r\n".join([
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'M-SEARCH * HTTP/1.1',
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'ST: {}'.format(ssdp_st),
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'MX: {:d}'.format(ssdp_mx),
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'MAN: "ssdp:discover"',
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'HOST: {}:{}'.format(*SSDP_TARGET),
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'', '']).encode('utf-8')
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# pylint: disable=invalid-name,too-many-locals,too-many-branches
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def scan(timeout=DISCOVER_TIMEOUT):
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"""Send a message over the network to discover uPnP devices.
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Inspired by Crimsdings
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https://github.com/crimsdings/ChromeCast/blob/master/cc_discovery.py
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Protocol explanation:
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https://embeddedinn.wordpress.com/tutorials/upnp-device-architecture/
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"""
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ssdp_requests = ssdp_request(ST_ALL), ssdp_request(ST_ROOTDEVICE)
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stop_wait = datetime.now() + timedelta(seconds=timeout)
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sockets = []
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for addr in zeroconf.get_all_addresses():
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try:
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sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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# Set the time-to-live for messages for local network
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sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL,
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SSDP_MX)
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sock.bind((addr, 0))
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sockets.append(sock)
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except socket.error:
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pass
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entries = {}
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for sock in [s for s in sockets]:
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try:
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for req in ssdp_requests:
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sock.sendto(req, SSDP_TARGET)
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sock.setblocking(False)
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except socket.error:
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sockets.remove(sock)
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sock.close()
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try:
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while sockets:
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time_diff = stop_wait - datetime.now()
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seconds_left = time_diff.total_seconds()
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if seconds_left <= 0:
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break
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ready = select.select(sockets, [], [], seconds_left)[0]
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for sock in ready:
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try:
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data, address = sock.recvfrom(1024)
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response = data.decode("utf-8")
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except UnicodeDecodeError:
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logging.getLogger(__name__).debug(
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'Ignoring invalid unicode response from %s', address)
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continue
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except socket.error:
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logging.getLogger(__name__).exception(
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"Socket error while discovering SSDP devices")
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sockets.remove(sock)
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sock.close()
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continue
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entry = UPNPEntry.from_response(response)
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entries[(entry.st, entry.location)] = entry
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finally:
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for s in sockets:
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s.close()
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return sorted(entries.values(), key=lambda entry: entry.location or '')
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def main():
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"""Test SSDP discovery."""
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from pprint import pprint
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print("Scanning SSDP..")
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pprint(scan())
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if __name__ == "__main__":
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main()
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