Discover Sonos zones on the local network.

    Return a set of `SoCo` instances for each zone found.
    Include invisible zones (bridges and slave zones in stereo pairs if
    ``include_invisible`` is `True`. Will block for up to ``timeout`` seconds,
     after which return `None` if no zones found.

    Args:
        timeout (int, optional): block for this many seconds, at most.
            Defaults to 5.
        include_invisible (bool, optional): include invisible zones in the
            return set. Defaults to `False`.
        interface_addr (str or None): Discovery operates by sending UDP
            multicast datagrams. ``interface_addr`` is a string (dotted
            quad) representation of the network interface address to use as
            the source of the datagrams (i.e. it is a value for
            `socket.IP_MULTICAST_IF <socket>`). If `None` or not specified,
            the system default interface for UDP multicast messages will be
            used. This is probably what you want to happen. Defaults to
            `None`.
    Returns:
        set: a set of `SoCo` instances, one for each zone found, or else
            `None`.

    Note:
        There is no easy cross-platform way to find out the addresses of the
        local machine's network interfaces. You might try the
        `netifaces module <https://pypi.python.org/pypi/netifaces>`_ and some
        code like this:

            >>> from netifaces import interfaces, AF_INET, ifaddresses
            >>> data = [ifaddresses(i) for i in interfaces()]
            >>> [d[AF_INET][0]['addr'] for d in data if d.get(AF_INET)]
            ['127.0.0.1', '192.168.1.20']

            This should provide you with a list of values to try for
            interface_addr if you are having trouble finding your Sonos devices

def discover(timeout=5, include_invisible=False, interface_addr=None):
    """ Discover Sonos zones on the local network.

    Return a set of `SoCo` instances for each zone found.
    Include invisible zones (bridges and slave zones in stereo pairs if
    ``include_invisible`` is `True`. Will block for up to ``timeout`` seconds,
     after which return `None` if no zones found.

    Args:
        timeout (int, optional): block for this many seconds, at most.
            Defaults to 5.
        include_invisible (bool, optional): include invisible zones in the
            return set. Defaults to `False`.
        interface_addr (str or None): Discovery operates by sending UDP
            multicast datagrams. ``interface_addr`` is a string (dotted
            quad) representation of the network interface address to use as
            the source of the datagrams (i.e. it is a value for
            `socket.IP_MULTICAST_IF <socket>`). If `None` or not specified,
            the system default interface for UDP multicast messages will be
            used. This is probably what you want to happen. Defaults to
            `None`.
    Returns:
        set: a set of `SoCo` instances, one for each zone found, or else
            `None`.

    Note:
        There is no easy cross-platform way to find out the addresses of the
        local machine's network interfaces. You might try the
        `netifaces module <https://pypi.python.org/pypi/netifaces>`_ and some
        code like this:

            >>> from netifaces import interfaces, AF_INET, ifaddresses
            >>> data = [ifaddresses(i) for i in interfaces()]
            >>> [d[AF_INET][0]['addr'] for d in data if d.get(AF_INET)]
            ['127.0.0.1', '192.168.1.20']

            This should provide you with a list of values to try for
            interface_addr if you are having trouble finding your Sonos devices

    """

    def create_socket(interface_addr=None):
        """ A helper function for creating a socket for discover purposes.

        Create and return a socket with appropriate options set for multicast.
        """

        _sock = socket.socket(
            socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
        # UPnP v1.0 requires a TTL of 4
        _sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL,
                         struct.pack("B", 4))
        if interface_addr is not None:
            _sock.setsockopt(
                socket.IPPROTO_IP, socket.IP_MULTICAST_IF,
                socket.inet_aton(interface_addr))
        return _sock

    # pylint: disable=invalid-name
    PLAYER_SEARCH = dedent("""\
        M-SEARCH * HTTP/1.1
        HOST: 239.255.255.250:1900
        MAN: "ssdp:discover"
        MX: 1
        ST: urn:schemas-upnp-org:device:ZonePlayer:1
        """).encode('utf-8')
    MCAST_GRP = "239.255.255.250"
    MCAST_PORT = 1900

    _sockets = []
    # Use the specified interface, if any
    if interface_addr is not None:
        try:
            address = socket.inet_aton(interface_addr)
        except socket.error:
            raise ValueError("{0} is not a valid IP address string".format(
                interface_addr))
        _sockets.append(create_socket(interface_addr))
        _LOG.info("Sending discovery packets on default interface")
    else:
        # Find the local network address using a couple of different methods.
        # Create a socket for each unique address found, and one for the
        # default multicast address
        addresses = set()
        try:
            addresses.add(socket.gethostbyname(socket.gethostname()))
        except socket.error:
            pass
        try:
            addresses.add(socket.gethostbyname(socket.getfqdn()))
        except socket.error:
            pass
        for address in addresses:
            try:
                _sockets.append(create_socket(address))
            except socket.error as e:
                _LOG.warning("Can't make a discovery socket for %s: %s: %s",
                             address, e.__class__.__name__, e)
        # Add a socket using the system default address
        _sockets.append(create_socket())
        # Used to be logged as:
        # list(s.getsockname()[0] for s in _sockets)
        # but getsockname fails on Windows with unconnected unbound sockets
        # https://bugs.python.org/issue1049
        _LOG.info("Sending discovery packets on %s", _sockets)

    for _ in range(0, 3):
        # Send a few times to each socket. UDP is unreliable
        for _sock in _sockets:
            _sock.sendto(really_utf8(PLAYER_SEARCH), (MCAST_GRP, MCAST_PORT))

    t0 = time.time()
    while True:
        # Check if the timeout is exceeded. We could do this check just
        # before the currently only continue statement of this loop,
        # but I feel it is safer to do it here, so that we do not forget
        # to do it if/when another continue statement is added later.
        # Note: this is sensitive to clock adjustments. AFAIK there
        # is no monotonic timer available before Python 3.3.
        t1 = time.time()
        if t1 - t0 > timeout:
            return None

        # The timeout of the select call is set to be no greater than
        # 100ms, so as not to exceed (too much) the required timeout
        # in case the loop is executed more than once.
        response, _, _ = select.select(_sockets, [], [], min(timeout, 0.1))

        # Only Zone Players should respond, given the value of ST in the
        # PLAYER_SEARCH message. However, to prevent misbehaved devices
        # on the network disrupting the discovery process, we check that
        # the response contains the "Sonos" string; otherwise we keep
        # waiting for a correct response.
        #
        # Here is a sample response from a real Sonos device (actual numbers
        # have been redacted):
        # HTTP/1.1 200 OK
        # CACHE-CONTROL: max-age = 1800
        # EXT:
        # LOCATION: http://***.***.***.***:1400/xml/device_description.xml
        # SERVER: Linux UPnP/1.0 Sonos/26.1-76230 (ZPS3)
        # ST: urn:schemas-upnp-org:device:ZonePlayer:1
        # USN: uuid:RINCON_B8*************00::urn:schemas-upnp-org:device:
        #                                                     ZonePlayer:1
        # X-RINCON-BOOTSEQ: 3
        # X-RINCON-HOUSEHOLD: Sonos_7O********************R7eU

        if response:
            for _sock in response:
                data, addr = _sock.recvfrom(1024)
                _LOG.debug(
                    'Received discovery response from %s: "%s"', addr, data
                )
                if b"Sonos" in data:
                    # Now we have an IP, we can build a SoCo instance and query
                    # that player for the topology to find the other players.
                    # It is much more efficient to rely upon the Zone
                    # Player's ability to find the others, than to wait for
                    # query responses from them ourselves.
                    zone = config.SOCO_CLASS(addr[0])
                    if include_invisible:
                        return zone.all_zones
                    else:
                        return zone.visible_zones