I am trying to send me a message over a mqtt connection and then perform a task on the received messages which are collected in the inbox. The problem is that when I run the code, the messages have not been received yet and the part in the code which shall work on the information in the messages does not run again.
I thought about using a while True: loop for that bit, but then the mqtt script won't be reached at all. This does not work.
This might be a very fundamental question, but how can I achieve running the mqtt client continuously and deal with the collected messages at some point later on?
import paho.mqtt.client as client
hostname = 'test.mosquitto.org'
topic = "personal/topic"
# receiving the data
inbox = []
def on_message(client, userdata, msg):
msg = msg.payload.decode()
inbox.append(msg)
print("Received Message No. %s: %s" % (len(inbox), msg))
def on_connect(client, userdata, flags, rc):
print("Connection returned result: " + str(rc))
client.subscribe(topic)
# this is where I want to perform a task on the message
y = []
X = []
for msg in inbox:
label, data = msg.split(': ')
data = data.split(', ')
y.append(label)
X.append(data)
# the mqtt part
client = client.Client()
client.on_message = on_message
client.on_connect = on_connect
client.connect(hostname)
client.loop_forever()
This is the construction using client.loop_start()at the end of the script (related to #hardillb's answer):
# the mqtt part
client = client.Client()
client.on_message = on_message
client.on_connect = on_connect
client.connect(hostname)
client.loop_start()
while True:
y = []
X = []
for msg in inbox:
label, data = msg.split(': ')
data = data.split(', ')
y.append(label)
X.append(data)
client.disconnect()
client.loop_stop()
The paho client can start it's network worker on a separate thread by using the client.loop_start() function.
You can then start your own processing loop after that, but the on_message callback function will run on the client's network worker thread, so if you want to queue up incoming messages to process later you will need to ensure that when you store the messages it is done in a thread safe manner.
Related
I am having an issue with the code below.
The code works perfectly at the beginning. First it says Connected to MQTT Broker! and receives data from it. But after a long time (like 6 hours, or 10 hours etc.) it says again Connected to MQTT Broker! and after that id does not receive any other data.
I am trying to make this program work forever, but i don't know what i have done wrong.
Any ideas?
# python3.6
import random
import mysql.connector
from paho.mqtt import client as mqtt_client
import json
# Code for MQTT Connection
broker = 'YOUR_BROKER'
port = 1883
topic = "YOUR_TOPIC"
# generate client ID with pub prefix randomly
client_id = f'python-mqtt-{random.randint(0, 100)}'
username = "THE_USERNAME"
password = "THE_PASSWORD"
# Function to connect on mqtt
def connect_mqtt() -> mqtt_client:
def on_connect(client, userdata, flags, rc):
if rc == 0:
print("Connected to MQTT Broker!")
else:
print("Failed to connect, return code %d\n", rc)
client = mqtt_client.Client(client_id)
client.username_pw_set(username, password)
client.on_connect = on_connect
client.connect(broker, port)
return client
# function to subscribe from mqtt
def subscribeFunc(client: mqtt_client):
def on_messageFunc(client, userdata, msg):
print(f"Received `{msg.payload.decode()}` from `{msg.topic}` topic")
client.subscribe(topic)
client.on_message = on_messageFunc
def run():
client = connect_mqtt()
subscribeFunc(client)
client.loop_forever()
if __name__ == '__main__':
run()
I tried to find the problem but it seems that nothing changed significantly.
I am expecting this program to receive data without stopping.
Network connections may not be 100% reliable (and servers etc are restarted from time to time) so expecting the connection to remain up forever is unrealistic. The issue with your code is that it connects then subscribes; if the connection is dropped it does not resubscribe. As the connection is clean_session=true and subscription qos=0 (the defaults) the broker will forget about any active subscriptions when the connection drops (so the client will reconnect but not receive any more messages).
The Simple solution is to use the approach shown in the docs and subscribe in the on_connect callback (that way the subscription will be renewed after reconnection):
def on_connect(client, userdata, flags, rc):
# Subscribing in on_connect() means that if we lose the connection and
# reconnect then subscriptions will be renewed.
client.subscribe("$SYS/#")
client = mqtt.Client()
client.on_connect = on_connect
client.connect("mqtt.eclipseprojects.io", 1883, 60)
You may also want to consider the advice in this answer (as per the comment from #mnikley) because that way the broker will queue up messages for you while the connection is down (otherwise these will be lost).
I am working with a device that publishes to the topic test/123, where 123 is the name of the device. I need to subscribe to that topic (and processes received messages); in addition I also need to send a word to the same topic (test/123). The device only looks at this topic.
How can I distinguish between incoming and outgoing by content? More precisely, how to send correctly. In the on_message method you need to do this or you need to create another method, but then how to receive incoming messages there. From the incoming messages I need to get the name of the device and then work with it.
import paho.mqtt.client as mqtt
import paho.mqtt.publish as publish
# The callback for when the client receives a CONNACK response from the server.
def on_connect(client, userdata, flags, rc):
print("Connected with result code "+str(rc))
# Subscribing in on_connect() means that if we lose the connection and
# reconnect then subscriptions will be renewed.
client.subscribe("/test/#")
# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
print(msg.topic+" "+str(msg.payload))
imei = msg.topic.split('test/')[1]
data = msg.payload.decode()
print(imei)
print(data)
publish(imei)
def publish(imei):
client = mqtt.Client()
user = 'test'
passw = '1111'
client.username_pw_set(user,passw)
client.connect("localhost",1883)
topic = '/test/'+ imei
client.publish(topic,'hello')
print('SEND')
client.disconnect()
client = mqtt.Client()
user = 'test'
passw = '1111'
client.username_pw_set(user,passw)
client.on_connect = on_connect
client.on_message = on_message
client.connect("localhost", 1883, 60)
client.loop_forever()
MQTT does not differentiate between clients in any way, that means if a client subscribes to a given topic it will receive ALL messages on that topic, including the ones it publishes it's self. So with your current design you will always get the message you publish in response to the first message back and this will trigger re-sending that message.
MQTT messages do NOT contain any information about who published the message unless you choose to add it to the payload, so you have no way to identify the incoming message as being the one you just published and this will cause a message loop storm.
The CORRECT solution is to not use the same topic for the 2 messages.
MQTT v5 has a flag that can be passed as part of establishing the connection
which prevents messages being returned to the client that published them. At this time it does not appear that the Paho Python library has a way to set this flag.
If you are using MQTT v3.1.1 and the mosquitto or RSMB MQTT broker then there is an undocumented option (this is not part of the MQTT spec) that can be set which will also prevent messages being returned. The following code will ONLY work with the 2 brokers I have mentioned.
import paho.mqtt.client as mqtt
# The callback for when the client receives a CONNACK response from the server.
def on_connect(client, userdata, flags, rc):
print("Connected with result code "+str(rc))
# Subscribing in on_connect() means that if we lose the connection and
# reconnect then subscriptions will be renewed.
client.subscribe("test/#")
# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
print(msg.topic+" "+str(msg.payload))
imei = msg.topic.split('test/')[1]
data = msg.payload.decode()
print(imei)
print(data)
publish(client, imei)
def publish(client,imei):
topic = 'test/'+ imei
client.publish(topic,'hello')
print('SEND')
client = mqtt.Client()
user = 'test'
passw = '1111'
client.username_pw_set(user,passw)
client.on_connect = on_connect
client.on_message = on_message
client.enable_bridge_mode()
client.connect("localhost", 1883, 60)
client.loop_forever()
p.s. do not start topics with a leading / while legal according to the spec, it will break things like shared subscriptions and adds an extra null to the start of the topic tree.
I am sending a number of messages simultaneously from multiple clients from one python script and trying to receive them on another script. The problem I am getting is that the message is received but only from the first client that gets connected and it keeps on looping over it.
What I need to have is that I get messages from each client in the manner they are published.
import paho.mqtt.client as mqtt
import time
def on_connect(client, userdata, flags, rc):
if rc == 0:
print("Connected to broker")
global Connected
Connected = True
else:
print("Connection failed")
def on_message(client, userdata, message):
print ("Message received: " + str(message.payload) + " from " + str(client))
Connected = False
client = mqtt.Client()
client.on_connect= on_connect
client.on_message= on_message
client.connect(host)
client.loop_start()
while Connected != True:
time.sleep(0.1)
client.subscribe("test")
print("subscribed")
client.loop_stop()
You are misunderstanding what the client argument in the on_message callback is.
This value is a link to the local instance of the MQTT client that has subscribed to the topic.
MQTT messages do not carry any information about the client that published them, unless you explicitly encode it into the payload. Part of the point of a Pub/Sub protocol like MQTT is to totally decouple the information creator (publisher) from the information consumer (subscriber).
Also you should move the call to client.subscribe("test") to inside the on_connect() callback because as you have it you are trying to resubscribe to the same topic 10 times a second which will achieve absolutely nothing, except to generate unneeded load on the broker.
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.
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
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)
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.
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 %d\n", 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
Here is the API available.
You just use client.is_connected() returns True or False.
Here is the code I'm running for my client. It works pretty well, but it doesn't allow python inputs to be made. I considered making another .py-file for typing and sending messages, but I'm not sure how to import the established connection.
Is it somehow possible to enable a python input chat using mqtt?
import paho.mqtt.client as mqtt
# The callback for when the client receives a CONNACK response from the server.
def on_connect(client, userdata, flags, rc):
print("Connected with result code "+str(rc))
# Subscribing in on_connect() means that if we lose the connection and
# reconnect then subscriptions will be renewed.
client.subscribe("hello/world")
# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
print(msg.topic+"| "+ userdate + " said: "+str(msg.payload))
id = raw_input('username: ')
client = mqtt.Client(id)
client.on_connect = on_connect
client.on_message = on_message
client.connect_async("192.168.0.24", 1883, 60)
# Blocking call that processes network traffic, dispatches callbacks and
# handles reconnecting.
# Other loop*() functions are available that give a threaded interface and a
# manual interface.
client.loop_forever()