MQTT – Is there a way to check if the client is still connected

Question

Is there a way to check if the client is still connected to the MQTT broker?

Something like

if client.isConnected(): # for example
    # if True then do stuff

Edit: There was instance where my Raspberry Pi stopped receiving from the client although it was still (from the look of it, the code was still showing updated results) running.

Here is the code since I may be doing something wrong:

client = mqtt.Client()
client.connect(address, 1883, 60)

while True:
    data = getdata()
    client.publish("$ahmed/",data,0)
    time.sleep(0.2)

The thing is that I was away, so I am not even sure why it stopped! Only if I restart my broker then it will start receiving again.

Asked By: Ahmed Al-haddad

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Source

Answer 1

I can’t see one in the doc but there are the on_disconnect on_connect callbacks that can be used to set your own state variable

EDIT:

You need to call one of the loop functions to give the client cycles to handle the network operations:

client = mqtt.Client()
client.connect(address, 1883, 60)

while True:
    data = getdata()
    client.publish("$ahmed/",data,0)
    client.loop(timeout=1.0, max_packets=1)
    time.sleep(0.2)

Answered By: hardillb

Answer 2

You can activate a flag in on_connect and deactivate it in on_disconnect. In this way you can know if the client is connected or not.

import paho.mqtt.client as mqtt

flag_connected = 0

def on_connect(client, userdata, flags, rc):
   global flag_connected
   flag_connected = 1

def on_disconnect(client, userdata, rc):
   global flag_connected
   flag_connected = 0

client = mqtt.Client()
client.on_connect = on_connect
client.on_disconnect = on_disconnect
client.connect(server,port)
client.loop_forever()
if flag_connected == 1:
   # Publish message
else:
   # Wait to reconnect

Answered By: Alejandro D

Answer 3

You can use will message to do this.

client=mqtt.Client()
client.will_set('will_message_topic',payload=time.time(),qos=2,retain=True)
client.connect(address,1883,60)
client.publish('will_message_topic',payload='I am alive',qos=2,retain=True)
client.loop_start()#this line is important
while 1:#faster than while True
    you loop

By leaving a will message, you can use another client to make sure if the client is online or not.

Answered By: Ian

Answer 4

Here is the API available.
You just use client.is_connected() returns True or False.

Answered By: Anil S

Answer 5

You can also view this article: How to use MQTT in Python (Paho)
A block of code from the article answering your question:

from paho.mqtt import client as mqtt_client


broker = 'broker.io'
port = 8888
client_id = 'client_id '
username = 'username'
password = 'password'


def connect_mqtt():
    def on_connect(client, userdata, flags, rc):
        if rc == 0:
            print("Connected to MQTT Broker!")
        else:
            print("Failed to connect, return code %dn", rc)
    # Set Connecting Client ID
    client = mqtt_client.Client(client_id)
    client.username_pw_set(username, password)
    client.on_connect = on_connect
    client.connect(broker, port)
    return client

Answered By: Motixa

MQTT – Is there a way to check if the client is still connected

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