How can I use paho MQTT client and live update of dash?

Dash Python
1

Hi,

I want to receive data from MQTT broker using paho-mqtt library. I want to display data on a live graph using plotly.
I wrote already a small script and it receives json-data from MQTT. I can olsa run “live update” example from dash documentation. But I don’t know how can I combine these two processes and how can I display MQTT data?

Thanks.

1 Like
2

Ok I solved my own question :slight_smile:

I was using client.loop_forever() function in paho mqtt library. This function is blocking and main thread doesn’t continue.
I used client.loop_start(). This function starts the loop in another thread and main thread can continue.

4

Can you post an example of the working code? I’m not able to get it working using loop_start() as you mentioned.

5

I can not post whole code but I post some pseudo code:

def on_message(client, userdata, message):
....
def on_connect(client, userdata, flags, rc):
    print("---Connected to MQTT Broker.")
    client.subscribe("topic")

app = dash.Dash(__name__)
app.index_string = ...
app.layout =  html.Main(...)

if __name__ == '__main__':
    client = mqtt.Client()
    client.on_connect = on_connect
    client.on_message = on_message
    client.username_pw_set(username = "debug", password = "debug")
    client.connect("localhost", 1883)
    client.loop_start()
    app.run_server(debug = True, port = portnumber_scoreapp, host='0.0.0.0')