loop_forever() timeout

[le0pa-RD]

Hello, I've been using this library to send and receive some data between an Arduino and a Raspberry Pi.
In the raspberry program, I connect to my Arduino and I read the messages containing the data I was searching for.
However, the Arduino sends data only one time while the receiving program runs in a loop.
I tried to set the loop_forever function with a timeout "client.loop_forever(60000, 1)" but when it times out it connects again to the client. Is there any way I can quit the program when loop_forever times out?

[lucacillario]

I'm not sure I understand your question. In any case i think that you have misunderstood the meaning of the timeout parameter. client.loop_forever(timeout=60000) does not mean "run the loop for 60000 seconds and after that break and quit the program". timeout refers to how long the thread must block on the socket waiting for new messages to be processed (incoming and / or outgoing). At the end of that timeout interval, if there are no new messages to process, the thread continues with its execution and will try again later.

If you want to stop the execution of your program after 60000 seconds, you could do this:

import time

client= mqtt.Client()
client.connect(broker,port)
client.loop_start()

# do stuff ...

time.sleep(60000)
client.disconnect()
client.loop_stop()

This is a very simplified solution, but if you explain better what you need to do I will gladly try to help you 😄 .

[le0pa-RD]

What I wanted to do is to set a timeout from the last message received, if no more messages are incoming and the timeout ends it quits the program.
If I understood what you did above your program just waits 60000 seconds from the loop start and then quits, right?

Thanks for the help :)

[lucacillario]

Yes, that's right.

So, if you need to quit the program after a certain period of not receiving any messages, you might try something like this:

from paho.mqtt.client import Client
import time


client = Client()
client.connect(broker, port)
client.loop_start()

run = True
TIMEOUT = 10  # seconds
while run:
	client._msgtime_mutex.acquire()
	last_msg_in = client._last_msg_in
	client._msgtime_mutex.release()
	now = time.monotonic()
	if now - last_msg_in > TIMEOUT:
	    client.disconnect()
	    client.loop_stop()
	    run = False
	else:
	    time.sleep(1)

In the example above I am accessing some private variables, and this is not great (but it's just an example). You could implement a timer that does the same thing, without having to access private variables. Keep in mind that with loop_start you end up in multithreaded environment, so even a simple timer needs to be handled with care.

Another way to solve your problem is to use a "special" message which, once received by the client, triggers the disconnection.

[le0pa-RD]

Thanks for the help

[lucacillario]

In any case I agree with you that the semantics of the timeout parameter, in the loop_forever function, is misleading. I'm not sure if that is bug or not. I'll try to investigate.