MQTT Client / subscriber

Senna

Hello

I am a student and for my final project I use a LoPy.
Great controller, lots of support, I/O, possibilities...
But now I ran into a problem.
I want to create an application that needs to send MQTT messages but also has to receive them.
The first part, sending MQTT messages, is not a problem and is working as described in the examples but I can't figure out how I can receive them.

I hope one of the more advanced users can help me.
Thank you a lot

This is my code:

def t3_publication(topic, msg):
    print (topic, ':', msg)
    pycom.rgbled(0xff00)

client = MQTTClient("d:j0y4ca:TestDevice:T04", "j0y4ca.messaging.internetofthings.ibmcloud.com", port=0,  user="use-token-auth", password="mytoken")

client.settimeout = timeout
client.connect()

client.set_callback(t3_publication)
client.subscribe("iot-2/evt/status")
time.sleep(1)
client.check_msg()

RobTuDelft

What is your full code (excluding sensitive details)?

Also can you post the result of?

import os
os.uname()

Senna

os.uname():

(sysname='LoPy', nodename='LoPy', release='1.0.1.b1', version='v1.8.6-264-gadacebe on 2016-12-22', machine='LoPy with ESP32')

main.py

from simple import MQTTClient
import machine
import time
import pycom

wlan = WLAN(mode=WLAN.STA)
wlan.antenna(WLAN.EXT_ANT)
wlan.connect("IoT", auth=(WLAN.WPA2, "MyPassword"), timeout=5000)

def t3_publication(topic, msg):
    print (topic, ':', msg)
    pycom.rgbled(0xff00)

while not wlan.isconnected():
     machine.idle()

client = MQTTClient("d:j0y4ca:TestDevice:T04", "j0y4ca.messaging.internetofthings.ibmcloud.com", port=0,  user="use-token-auth", password="MyToken")

client.settimeout = 5
client.connect()

client.set_callback(t3_publication)
client.subscribe("iot-2/evt/status")
time.sleep(1)
client.check_msg()

simple.py

import ustruct as struct


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.addr = socket.getaddrinfo(server, port)[0][-1]
        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()
        self.sock.connect(self.addr)
        if self.ssl:
            import ussl
            self.sock = ussl.wrap_socket(self.sock, **self.ssl_params)
        msg = bytearray(b"\x10\0\0\x04MQTT\x04\x02\0\0")
        msg[1] = 10 + 2 + len(self.client_id)
        msg[9] = clean_session << 1
        if self.user is not None:
            msg[1] += 2 + len(self.user) + 2 + len(self.pswd)
            msg[9] |= 0xC0
        if self.keepalive:
            assert self.keepalive < 65536
            msg[10] |= self.keepalive >> 8
            msg[11] |= self.keepalive & 0x00FF
        if self.lw_topic:
            msg[1] += 2 + len(self.lw_topic) + 2 + len(self.lw_msg)
            msg[9] |= 0x4 | (self.lw_qos & 0x1) << 3 | (self.lw_qos & 0x2) << 3
            msg[9] |= self.lw_retain << 5
        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)
        print(res)
        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()

RobTuDelft

@Senna
Your firmware is outdated, please update to the latest v1.6.13.b1.

Don't use simple.py anymore, it is also outdated.
Instead go to mqtt and download the new library file there.

Also check out week 4 of Alex's corner where he explains how to use it.

bucknall

Hi @Senna,

I'm waiting for the docs updates to be pushed live but you'll see an update made to the docs.pycom.io page for MQTT that matches my Alex's Corner video explaining how it all works!

Might be useful to you!

https://youtu.be/3NDPSbr5J14?list=PLS09TA19umCOavPeP_FoMHoCuCzjJUWQk

misterlisty

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