MQTT client for ESP on micropython

Based on the ESP-MicroPython codebase an example of a mqtt client.

The original example is here
https://github.com/RuiSantosdotme/ESP-MicroPython/blob/master/code/MQTT/MQTT_Hello_World/ESP_1/main.py

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from umqttsimple import MQTTClient
import network
import ubinascii
import machine
import time


WIFI_SSID = "..."
WIFI_PASS = "..."
# server is test.mosquitto.org
MQTT_SERVER = "5.196.95.208"
MQTT_CLIENTID = "test"
MQTT_TOPIC = "hello-esp"


def sub_cb(topic, msg):
    print('ESP received hello message')
    print((topic, msg))


def connect_and_subscribe(mqtt_server, client_id, topic_sub):
    client = MQTTClient(ubinascii.hexlify(client_id), mqtt_server)
    client.set_callback(sub_cb)
    client.connect()
    client.subscribe(topic_sub)
    print('Connected to %s MQTT broker, subscribed to %s topic' %
          (mqtt_server, topic_sub))
    return client


def restart_and_reconnect():
    print('Failed to connect to MQTT broker. Reconnecting...')
    time.sleep(10)
    machine.reset()


def connect_mqtt(mqtt_server, client_id, topic_sub):
    try:
        client = connect_and_subscribe(mqtt_server, client_id, topic_sub)
    except OSError as err:
        restart_and_reconnect()

    counter = 0
    message_interval = 10
    last_message = 0

    while True:
        try:
            client.check_msg()
            if (time.time() - last_message) > message_interval:
                msg = b'Hello #%d' % counter
                client.publish(topic_sub, msg)
                last_message = time.time()
                counter += 1
        except OSError as err:
            print("restarting, err", err)
            restart_and_reconnect()


def connect_wifi():
    print("Connecting to " + WIFI_SSID)
    station = network.WLAN(network.STA_IF)
    station.active(True)
    station.connect(WIFI_SSID, WIFI_PASS)
    while station.isconnected() == False:
        pass
    print('wifi connected')
    print(station.ifconfig())


def run():
    connect_wifi()
    connect_mqtt(MQTT_SERVER, MQTT_CLIENTID, MQTT_TOPIC)


if __name__ == '__main__':
    run()