python paho mqtt can not connect to mqtts with username and password

Question

The following python code on my raspberrypi doesn't connect to my mqtt broker, it just hangs after printing Connecting...:

import paho.mqtt.client as mqtt

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe("test")


def on_message(client, userdata, msg):
    print(msg.topic+" "+str(msg.payload))


client = mqtt.Client(client_id="",clean_session=True,userdata=None,protocol=mqtt.MQTTv311,transport="tcp")
client.on_connect = on_connect
client.on_message = on_message

client.username_pw_set(username="stackoverflow",password="stackoverflow")
print("Connecting...")
client.connect("learn.evermight.net", 9101, 10)
client.loop_forever()

What did I do wrong with my Python code?

Command Line Success

I confirmed that my mqtt does work because I can subscribe from terminal with this command:

mosquitto_sub -h learn.evermight.net -p 9101 -t "test" -u "stackoverflow" -P "stackoverflow" --capath /etc/ssl/certs/

And I will see messages in my terminal as soon as I run this command from another terminal

mosquitto_pub -h learn.evermight.net -p 9101 -t "test" -u "stackoverflow" -P "stackoverflow" -m "hello world" --capath /etc/ssl/certs/

What is wrong with my python code?

NodeJS Success

Additionally, the following NodeJS code also works for connecting and publishing to my MQTT server.

const mqtt = require('async-mqtt');

  try{
    const client = await mqtt.connectAsync("mqtts://learn.evermight.net",{
      port:9101,
      host:"mqtts://learn.evermight.net",
      username:"stackoverflow",
      password:"stackoverflow",
      connectTimeout:5000,
      protocolId:"MQIsdp",
      protocolVersion:3,
      encoding:"utf8",
      keepalive: 60
    });
    await client.publish("test","hello world");
    await client.end();
  } catch(e) {
    console.log(e);
  }

Website JavaScript Success

And the following code can also connect to a websocket port via web browser javascript website, subscribe to the test topic and receive published messages (note that my websockets use port 9102)

import Paho from "paho-mqtt";

const client = new Paho.Client("learn.evermight.net",9102,"WebBrowser");
  client.onConnectionLost = response=>console.log("lostMQTTConnection: " +(response.errorCode !== 0 ? response.errorMessage : "Unknown MQTT Error" ));
  client.onMessageArrived = message=>console.log(message.payloadString);
  client.connect({
    onSuccess:_=>client.subscribe("test"),
    useSSL:true,
    userName:"stackoverflow",
    password:"stackoverflow",
  });

why do you know if it hangs ? loop_forever() should runs code all the time until you kill it. — furas
as for me all problem can be --capath /etc/ssl/certs/. When I run your code with my broker then it runs, and when I run mosquitto_pub without --capath /etc/ssl/certs/ then it also runs but I get Error: Connection refused when I use --capath /etc/ssl/certs/. Probably in code you would have to use something similar to --capath /etc/ssl/certs/ — furas
@furas I updated my code to give real credentials to my mqtt server and I give real working examples in bash, nodejs and plain javascript. The only thing that fails is my python code. Does my server work for your python script? — John
it doesn't work with Python. It works only with mosquitto_sub/mosquitto_pub so I can connect. There are command client.tls_set() and client.tls_set_context() and maybe they could help. But I never had to use it. I have own MTTQ in local network so I didn't bother to use certs — furas

furas furas · Accepted Answer · 2020-06-20T02:29:30

I found that I can connect if I add this command without arguments

client.tls_set()

In paho documentation at the end of description for tls_set() you can see

Must be called before connect*().

but it works for me event after client.connect()

In the same domentation you can see that without arguments it uses defult system settings

By default, on Python 2.7.9+ or 3.4+,  
the default certification authority of the system is used. 

On older Python version this parameter is mandatory.

It is needed only if mosquitto_sub/mosquitto_pub needs --capath /etc/ssl/certs/.
If mosquitto_sub/mosquitto_pub works without --capath /etc/ssl/certs/ then don't use it.

import paho.mqtt.client as mqtt

def on_connect(client, userdata, flags, rc):
    print("Connected with result code", rc)
    client.subscribe("test")

def on_message(client, userdata, msg):
    print(msg.topic, msg.payload)


client = mqtt.Client(client_id="", clean_session=True, userdata=None, protocol=mqtt.MQTTv311, transport="tcp")
client.on_connect = on_connect
client.on_message = on_message

client.tls_set()  # <--- even without arguments

client.username_pw_set(username="stackoverflow", password="stackoverflow")
print("Connecting...")
client.connect("learn.evermight.net", 9101, 10)
client.loop_forever()

python paho mqtt can not connect to mqtts with username and password

1 Answers