def __init__(self, uri, host, port, rate):

        """sends UDP messages to the given host/port"""

        super().__init__(uri, rate)

        packet = bytearray()

        packet.extend(map(ord, "Art-Net"))

        packet.append(0x00)  # Null terminate Art-Net

        packet.extend([0x00, 0x50])  # Opcode ArtDMX 0x5000 (Little endian)

        packet.extend([0x00, 0x0e])  # Protocol version 14

        self.base_packet = packet

        self.sequence_counter = 255

        self._socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    def _write(self, buf):

        with metrics('write', output=self.shortId()).time():

            if not buf:

                logAllDmx.debug('%s: empty buf- no output', self.shortId())

                return

            if logAllDmx.isEnabledFor(logging.DEBUG):

                # for testing fps, smooth fades, etc

                logAllDmx.debug('%s: %s...' % (self.shortId(), ' '.join(map(str, buf[:32]))))

            if self.sequence_counter:

                self.sequence_counter += 1

                if self.sequence_counter > 255:

                    self.sequence_counter = 1

            packet = self.base_packet[:]

            packet.append(self.sequence_counter)  # Sequence,

            packet.append(0x00)  # Physical

            universe_nr = 0

            packet.append(universe_nr & 0xFF)  # Universe LowByte

            packet.append(universe_nr >> 8 & 0xFF)  # Universe HighByte

            packet.extend(struct.pack('>h', len(buf)))  # Pack the number of channels Big endian

            packet.extend(buf)

            self._socket.sendto(packet, ('127.0.0.1', 6454))

class Udmx(BackgroundLoopOutput):

    """alternate lib:

    from PyDMXControl.controllers import uDMXController

    u = uDMXController(autostart=False)

    u._connect()

    u._transmit([255, 0, 0, ...

    """

        self.bus = bus

        self.address = address

        self.lastDmxChannel = lastDmxChannel

        self.dev = None

        super().__init__(uri, rate=rate)

        self.reconnect()

    def shortId(self) -> str:

        return super().shortId() + f'_bus={self.bus}'

    def reconnect(self):

        metrics('connected', output=self.shortId()).set(0)

        from pyudmx import pyudmx

        self.dev = pyudmx.uDMXDevice()

        if not self.dev.open(bus=self.bus, address=self.address):

            raise ValueError("dmx open failed")

        log.info(f'opened {self.dev}')

        metrics('connected', output=self.shortId()).set(1)

        metrics('reconnections', output=self.shortId()).inc()

    #def update(self, buf:bytes):

    #    self._write(buf)

    #def _loop(self):

    #    pass

    def _write(self, buf):

        if not self.dev:

            log.info('%s: trying to connect', self.shortId())

            raise ValueError()

        with metrics('write', output=self.shortId()).time():

            try:

                if not buf:

                    logAllDmx.debug('%s: empty buf- no output', self.shortId())

                    return

                # ok to truncate the last channels if they just went

                # to 0? No it is not. DMX receivers don't add implicit

                # zeros there.

                buf = buf[:self.lastDmxChannel]

                if logAllDmx.isEnabledFor(logging.DEBUG):

                    # for testing fps, smooth fades, etc

                    logAllDmx.debug('%s: %s...' % (self.shortId(), ' '.join(map(str, buf[:32]))))

                t1 = time.time()

                sent = self.dev.send_multi_value(1, bytearray(buf))

                if sent != len(buf):