QUERY · ISSUE

can't await mqtt.simple publish method

openby alirezaimiopened 2019-10-22updated 2020-01-07

Hi
I'm using umqtt.simple and there is problem when i await mqtt.publish in my code !
'NoneType' object isn't iterable
Is there any way to solve this issue ?
Or use other lib like https://github.com/peterhinch/micropython-mqtt/blob/master/mqtt_as ?

2 comments

2niuhe · 2020-01-06

The umqtt.simple module is sync.You'd better use peterhinch's uasync mqtt lib.

While you only need subscribe to some topic.
my solution is :

use check_msg() instead of wait_msg(),cause check_msg() return immediately.

import uasyncio
from umqtt.simple import MQTTClient

loop = uasyncio.get_event_loop()
async def my_callback(topic,msg):
   await uasyncio.sleep(1)
   
def sub_callback(topic, msg):
   global loop
   loop.create_task(my_callback(topic,msg))

async def my_main():
   c = MQTTClient("umqtt_client", server)
   c.set_callback(sub_callback)
   c.connect()
   c.subscribe(b'foo_con')
   pass

loop.creat_task(my_main())
loop.run_forever()

alirezaimi · 2020-01-07

@2niuhe thanks, but using umqtt_async have its own problem : https://forum.micropython.org/viewtopic.php?f=15&t=7144

thanks for your solution but i had problem in publish part not others .

CANDIDATE · PULL REQUEST

wait_msg() return op as indication if there was a message

closedby meirarmonopened 2022-09-06updated 2022-10-04

As indicated in this issue: https://github.com/micropython/micropython-lib/issues/328, it would be useful if wait_msg() would return a value if a message was received.
A common use case using this library would be:

def callback(topic, msg):
    print(topic, msg)


async def check_messages(mqtt_client, interval):
    while True:
        mqtt_client.check_msg()
        await asyncio.sleep(interval)

In the above scenario, if more than one message was published to the topic being subscribed to, it will still get consumed every <interval> seconds. If this change is merged, we would be able to do:

def callback(topic, msg):
    print(topic, msg)


async def check_messages(mqtt_client, interval):
    while True:
        while mqtt_client.check_msg() is not None:
            continue
        await asyncio.sleep(interval)

And any waiting messages will get consumed immediately.

1 comment

dpgeorge · 2022-10-04

Thanks for the contribution, this is a nice and simple improvement. Rebased and merged in b50d3462d783e4aab2f10d6b8117641244918f64

can't await mqtt.simple publish method

wait_msg() return op as indication if there was a message

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