State of client doesn't change to disconnected after connection lost

[mohsen-mahmoodi]

When not using loop_forever or loop_start and running the loop in the main thread, a hard disconnect gets captured by the client but doesn't change the output of is_connected() method.

Steps to reproduce:

1. Run an mqtt server, I use emqx:

docker run -d --name emqx -p 18083:18083 -p 1883:1883 emqx/emqx:v4.0.0

2. Run the code below:

import time
import logging

import paho.mqtt.client as mqtt

logging.basicConfig(level=logging.DEBUG)

logger = logging.getLogger(__name__)


def on_connect(client, userdata, flags, rc):
    logger.debug('Connected with result code ' + str(rc))
    # subscribe
    client.subscribe('tienda/#')


def on_message(client, userdata, msg):
    logger.debug(msg.topic + " " + str(msg.payload))
    # if b'stop' in msg.payload:
    #     client.disconnect()


def on_disconnect(client, flags, rc):
    logger.debug('Disconnected with result code ' + str(rc))
    # client.reconnect()

# Build the client

client = mqtt.Client(clean_session=True)
logger.error('Client initialized with status: %s', client._state)
# Specify callback function
client.on_connect = on_connect
client.on_message = on_message
client.on_disconnect = on_disconnect
client.enable_logger(logger)
# client.username_pw_set('topse', 'cret')


# Establish a connection
client.connect('localhost', 1883, 60)
# wait for connection
while not client.is_connected():
    logger.debug('Connecting')
    client.loop(timeout=1)

logger.debug('Connected')

# This loops never ends even after there is no connection at all
while client.is_connected():
    client.loop()
    time.sleep(1)
    logger.debug('In main loop: %s', client.is_connected())

3. browse http://localhost:18083/#/clients and find you client and disconnect it.

The result is that you will see the Disconnected with result code: 0 message, but the program never exits and keeps printing:

DEBUG:__main__:In main loop: True
DEBUG:__main__:In main loop: True
DEBUG:__main__:In main loop: True
DEBUG:__main__:In main loop: True
DEBUG:__main__:In main loop: True

The problem is the internal field _state doesn't changes to disconnected or any other states when we are not calling the disconnect method directly. This causes the is_connected() method return true and the loop never exits.

paho-mqtt version: 1.5.1

[mohsen-mahmoodi]

Running the loop just like loop_forever() has no problem:

while True:
    rc = 0
    while rc == 0:
        logger.debug(client._state)
        rc = client.loop()
        time.sleep(2)

    try:
        client.reconnect()
    except (socket.error, OSError, WebsocketConnectionError):
        logger.error("Connection failed, retrying") 

The problem is that is_connected() returns wrong result.

[kpfleming]

Possibly related to #441.

[PierreF]

I'm able to reproduce this with the sample code your provided and killing the broken after log of In main loop.
I've used Mosquitto rather than emqx but this shouldn't matter.

#795 fix the issue in my test scenario.