I wrote a simple python program to connect RabbitMqtt server and hope to generate a queue and publish messages. However, after building the connection and creating a queue, the message was not published successfully (when I check the information of message, I cannot find any records and data). I wonder I miss some parameters or setting in client.publish(), but I do not know how to figure it out.
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('SEEDQ')
client.publish('SEEDQ', 'deqwdqwefqwefwefqwefqwe', 0, False)
# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
print(msg.topic + " " + str(msg.payload))
client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect("15.78.xx.xx", 1883, 60)
client.loop_forever()
The problem is that you are calling client.publish() before the connection is complete. Move the client.publish into the on_connect function, AFTER client.subscribe('SEEDQ') and it will work.
# 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("$SYS/#")
client.subscribe('SEEDQ')
client.publish('SEEDQ', 111, 0, False)
Output:
Connected with result code 0
SEEDQ 111
FYI I used the public test server at iot.eclipse.org, port 1883.
FYI there is a very useful browser client HERE -using this and the public test server messagesight.demos.ibm.com port 1883 you can subscribe to SEEDQ and see your python script publish, and also using the browser client you can publish to SEEDQ from your browser and your script will display the message while it is in the loop_forever(). Obviously using these test servers is public visible.
UPDATE here is the complete code - this works against the public servers I show above.
import paho.mqtt.client as mqtt
# The callback for when the client receives a CONNACK response from the server.
def on_connect(client, userdata, flags, rc):
print("Connected with result code "+str(rc))
# Subscribing in on_connect() means that if we lose the connection and
# reconnect then subscriptions will be renewed.
# client.subscribe("$SYS/#")
client.subscribe('SEEDQ')
client.publish('SEEDQ', 111, 0, False)
# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
print(msg.topic+" "+str(msg.payload))
client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
#client.connect('15.xx.xx.xx', 1883, 60)
#client.connect("iot.eclipse.org", 1883, 60)
client.connect("messagesight.demos.ibm.com", 1883, 60)
#client.publish('SEEDQ', 111, 0, False)
# 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()
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'm using this python script to implement a Paho(MQTT) subscriber but i am unable get any responce messages.i am able to subscribe mqtt brokerin command prompt by using mosquitto_sub -t "" -d -h -p 8883 --psk foo --psk-identity bar --insecure --tls-version tlsv1
import paho.mqtt.client as mqtt
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("*********")
def on_message(client, userdata, msg):
print(msg.topic+" "+str(msg.payload))
client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect("*********", 8883, 60)
client.loop_forever()
When I run above python script then it does not respond any error or message but keep going with loop , I also run it line by line and when I run client.connect("*********", 8883, 60) then it shows only 0 . please note here without psk and psk-identity we cannot connect to broker.
Thanks
Please check with your topic carefully, sometimes missing of / or # cause this problem.
or
Try This
def on_message(client, userdata, msg):
print("Message Recieved from broker: " + msg.payload.decode())
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()