>>> import mqtest
dbug-msg: 0x9 b'04:4d:51:54:54:04:02:00:00'
dbug-resp: b' \x02\x00\x00'
connect: 0
publish: None
disconnect: None

>>> import mqtest
dbug-msg: 0x9 b'04:4d:51:54:54:04:02:00:00'
dbug-resp: b''
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "mqtest.py", line 37, in <module>
  File "mqtest.py", line 33, in go
  File "umqtt_robust.py", line 101, in connect
IndexError: bytes index out of range

from umqtt_robust import MQTTClient

id      = b'484a300173f0'
host    = b'mqtt.thingspeak.com'
port    = 1883
retain  = False
topic   = "channels/MY-CHANNEL-ID/publish/MY-ACCESS-KEY"
data    = 'field6=100&field5=4019&field4=64.20001&field3=29.5&field2=73.1&field1=29.5&field8={"last_stamp": 1495097691048, "update_secs": 300, "name": "Room", "devid": "484a300173f0"}&status=MQTTPUBLISH&field7=-9318.205'

client = MQTTClient(id,host,port=port)

def go():
  print('connect:',client.connect())
  print('publish:',client.publish(topic,data,retain=retain))
  print('disconnect:',client.disconnect());

go()

    def connect(self, clean_session=True):
        self.sock = socket.socket()
        addr = socket.getaddrinfo(self.server, self.port)[0][-1]
        self.sock.connect(addr)
        if self.ssl:
            import ussl
            self.sock = ussl.wrap_socket(self.sock, **self.ssl_params)
        premsg = bytearray(b"\x10\0\0\0\0\0")
        msg = bytearray(b"\x04MQTT\x04\x02\0\0")

        sz = 10 + 2 + len(self.client_id)
        msg[6] = clean_session << 1
        if self.user is not None:
            sz += 2 + len(self.user) + 2 + len(self.pswd)
            msg[6] |= 0xC0
        if self.keepalive:
            assert self.keepalive < 65536
            msg[7] |= self.keepalive >> 8
            msg[8] |= self.keepalive & 0x00FF
        if self.lw_topic:
            sz += 2 + len(self.lw_topic) + 2 + len(self.lw_msg)
            msg[6] |= 0x4 | (self.lw_qos & 0x1) << 3 | (self.lw_qos & 0x2) << 3
            msg[6] |= self.lw_retain << 5

        i = 1
        while sz > 0x7f:
            premsg[i] = (sz & 0x7f) | 0x80
            sz >>= 7
            i += 1
        premsg[i] = sz

        self.sock.write(premsg, i + 2)
        self.sock.write(msg)
        print('dbug-msg:',hex(len(msg)), hexlify(msg, ":"))
        self._send_str(self.client_id)
        if self.lw_topic:
            self._send_str(self.lw_topic)
            self._send_str(self.lw_msg)
        if self.user is not None:
            self._send_str(self.user)
            self._send_str(self.pswd)
        resp = self.sock.read(4)
        print('dbug-resp:',resp)
        assert resp[0] == 0x20 and resp[1] == 0x02
        if resp[3] != 0:
            raise MQTTException(resp[3])
        return resp[2] & 1