mqtt subscription doesn't work on ESP32

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lazarvgd
Posts: 39
Joined: Sun May 20, 2018 8:57 am

mqtt subscription doesn't work on ESP32

Post by lazarvgd » Fri Apr 16, 2021 12:15 pm

Hello I am trying to subscribe and print message form mqtt but for some reason my code doesn't work and I don't getting anything in console. But I am able to publish messages without any problem. Can you please help me with this? What am I missing? P.S. The board is connected to WIFI and getting time from NTP.

Here is my code:
main.py

Code: Select all

from machine import Pin
from machine import RTC
from machine import WDT
import time
import ntptime
import utime
import board_net
import gc
import esp
from machine import UART
from mqtt import MQTTClient

esp.osdebug(None)
gc.collect()

client = None

uart = UART(1, baudrate=115200)
uart.init(115200, bits=8, parity=None, stop=1)

def subscribe_callback(topic, msg): 
	print((topic, msg))
	client.publish(b'/time', str(utime.localtime()))

def setup_mqtt():
	print('setup_mqtt...')
	global client
	client=MQTTClient("esp32", "192.168.1.53",user="mqtt_client", password="password", port=1883) 
	client.set_callback(subscribe_callback)
	client.connect()
	client.subscribe(b'/test')
	# client.subscribe(b'/time')
	client.subscribe(b'/home')
	
	print('All done setup_mqtt!') 

def set_time():
	ntptime.settime()
	t = utime.gmtime()
	h = t[3]
	t_modified=(t[0],t[1],t[2],h,t[4],t[5],t[6],t[7])
	rtc = RTC()
	rtc.init(t)

# wdt = WDT(timeout=12000)
board_net.do_connect()

led = Pin(2, Pin.OUT)
set_time()
setup_mqtt()
while True:
	led.on()
	data = uart.read(1)
	if data is not None:
		print("Data received = ", data)
		uart.write('abc')
	time.sleep(1)
	led.off()
	client.publish(b'/time', (str(utime.localtime())))
	time.sleep(1)
	if utime.gmtime()[5] % 2 == 0:
		client.publish(b'/test', 'Hello test :)')
	# wdt.feed()
And mqtt.py

Code: Select all

try:
    import usocket as socket
except:
    import socket
import ustruct as struct
from ubinascii import hexlify

class MQTTException(Exception):
    pass

class MQTTClient:

    def __init__(self, client_id, server, port=0, user=None, password=None, keepalive=0,
                 ssl=False, ssl_params={}):
        if port == 0:
            port = 8883 if ssl else 1883
        self.client_id = client_id
        self.sock = None
        self.server = server
        self.port = port
        self.ssl = ssl
        self.ssl_params = ssl_params
        self.pid = 0
        self.cb = None
        self.user = user
        self.pswd = password
        self.keepalive = keepalive
        self.lw_topic = None
        self.lw_msg = None
        self.lw_qos = 0
        self.lw_retain = False

    def _send_str(self, s):
        self.sock.write(struct.pack("!H", len(s)))
        self.sock.write(s)

    def _recv_len(self):
        n = 0
        sh = 0
        while 1:
            b = self.sock.read(1)[0]
            n |= (b & 0x7f) << sh
            if not b & 0x80:
                return n
            sh += 7

    def set_callback(self, f):
        self.cb = f

    def set_last_will(self, topic, msg, retain=False, qos=0):
        assert 0 <= qos <= 2
        assert topic
        self.lw_topic = topic
        self.lw_msg = msg
        self.lw_qos = qos
        self.lw_retain = retain

    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(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)
        assert resp[0] == 0x20 and resp[1] == 0x02
        if resp[3] != 0:
            raise MQTTException(resp[3])
        return resp[2] & 1

    def disconnect(self):
        self.sock.write(b"\xe0\0")
        self.sock.close()

    def ping(self):
        self.sock.write(b"\xc0\0")

    def publish(self, topic, msg, retain=False, qos=0):
        pkt = bytearray(b"\x30\0\0\0")
        pkt[0] |= qos << 1 | retain
        sz = 2 + len(topic) + len(msg)
        if qos > 0:
            sz += 2
        assert sz < 2097152
        i = 1
        while sz > 0x7f:
            pkt[i] = (sz & 0x7f) | 0x80
            sz >>= 7
            i += 1
        pkt[i] = sz
        #print(hex(len(pkt)), hexlify(pkt, ":"))
        self.sock.write(pkt, i + 1)
        self._send_str(topic)
        if qos > 0:
            self.pid += 1
            pid = self.pid
            struct.pack_into("!H", pkt, 0, pid)
            self.sock.write(pkt, 2)
        self.sock.write(msg)
        if qos == 1:
            while 1:
                op = self.wait_msg()
                if op == 0x40:
                    sz = self.sock.read(1)
                    assert sz == b"\x02"
                    rcv_pid = self.sock.read(2)
                    rcv_pid = rcv_pid[0] << 8 | rcv_pid[1]
                    if pid == rcv_pid:
                        return
        elif qos == 2:
            assert 0

    def subscribe(self, topic, qos=0):
        assert self.cb is not None, "Subscribe callback is not set"
        pkt = bytearray(b"\x82\0\0\0")
        self.pid += 1
        struct.pack_into("!BH", pkt, 1, 2 + 2 + len(topic) + 1, self.pid)
        #print(hex(len(pkt)), hexlify(pkt, ":"))
        self.sock.write(pkt)
        self._send_str(topic)
        self.sock.write(qos.to_bytes(1, "little"))
        while 1:
            op = self.wait_msg()
            if op == 0x90:
                resp = self.sock.read(4)
                # print(resp)
                assert resp[1] == pkt[2] and resp[2] == pkt[3]
                if resp[3] == 0x80:
                    raise MQTTException(resp[3])
                return

    # Wait for a single incoming MQTT message and process it.
    # Subscribed messages are delivered to a callback previously
    # set by .set_callback() method. Other (internal) MQTT
    # messages processed internally.
    def wait_msg(self):
        res = self.sock.read(1)
        self.sock.setblocking(True)
        if res is None:
            return None
        if res == b"":
            raise OSError(-1)
        if res == b"\xd0":  # PINGRESP
            sz = self.sock.read(1)[0]
            assert sz == 0
            return None
        op = res[0]
        if op & 0xf0 != 0x30:
            return op
        sz = self._recv_len()
        topic_len = self.sock.read(2)
        topic_len = (topic_len[0] << 8) | topic_len[1]
        topic = self.sock.read(topic_len)
        sz -= topic_len + 2
        if op & 6:
            pid = self.sock.read(2)
            pid = pid[0] << 8 | pid[1]
            sz -= 2
        msg = self.sock.read(sz)
        self.cb(topic, msg)
        if op & 6 == 2:
            pkt = bytearray(b"\x40\x02\0\0")
            struct.pack_into("!H", pkt, 2, pid)
            self.sock.write(pkt)
        elif op & 6 == 4:
            assert 0

    # Checks whether a pending message from server is available.
    # If not, returns immediately with None. Otherwise, does
    # the same processing as wait_msg.
    def check_msg(self):
        self.sock.setblocking(False)
        return self.wait_msg()

User avatar
glenn20
Posts: 132
Joined: Mon Jun 04, 2018 10:09 am

Re: mqtt subscription doesn't work on ESP32

Post by glenn20 » Sat Apr 17, 2021 2:05 am

It seems that your mqtt.py is the same as umqtt.simple, in which case, you need to explicitly check for messages from the broker before subscribe_callback will be invoked.

Just add client.check_msg() in your processing loop.

Depending on how responsive you want your app to be, you might want to change your sleep(1) into something like:

Code: Select all

for _ in range(10):
	client.check_msg()
	time.sleep(0.1)
Alternatively, if you are comfortable with asyncio, you could look at https://github.com/peterhinch/micropyth ... er/mqtt_as by @peterhinch.

lazarvgd
Posts: 39
Joined: Sun May 20, 2018 8:57 am

Re: mqtt subscription doesn't work on ESP32

Post by lazarvgd » Sat Apr 17, 2021 9:04 am

Thank you so much! This is the problem that I compered files and still didn't see the issue.
Awesome! Cheer!

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