Is it posible to listen to an MQTT server and publish with Websocket (endpoint) from our own server

Question

I have got an mqtt consumer that listens to a topic and based on that, I used to send a response on another topic. However now I would like to create a Websocket Secure wss endpoint where i could stream this processed information. Could you tell me if it is possible to do that wth mqttasgi library, if yes how.

Here I leave the code of my consumer.

from mqttasgi.consumers import MqttConsumer
from mqtt_handler.tasks import processmqttmessage

import json

class MyMqttConsumer(MqttConsumer):

async def connect(self):
    await self.subscribe('application/+/device/+/event/up', 2)
    await self.channel_layer.group_add("stracontech", self.channel_name)

async def receive(self, mqtt_message):
    print('Received a message at topic:', mqtt_message['topic'])
    print('With payload', mqtt_message['payload'])
    print('And QOS:', mqtt_message['qos'])
    dictresult = json.loads(mqtt_message['payload'])
    jsonresult = json.dumps(dictresult)
    processmqttmessage.delay(jsonresult, mqtt_message['topic'])
    pass

async def publish_results(self, event):
    data = event['result']
    await self.publish("stracontech/procesed/"+event['result']['device_id']+"/result", json.dumps(data).encode('utf-8'), qos=2, retain=False)

async def disconnect(self):
    await self.unsubscribe('application/+/device/+/event/up')

Pd: @Santiago Ivulich maybe you can help me with that.

score 0 · Accepted Answer · answered Jun 18 '22 at 17:59

For Websocket consumer you need to follow the guide in channels.

An example:

from channels.generic.websocket import AsyncWebsocketConsumer

class MyConsumer(AsyncWebsocketConsumer):
    groups = ["broadcast"]

    async def connect(self):
        # Called on connection.
        # To accept the connection call:
        await self.accept()
        # Or accept the connection and specify a chosen subprotocol.
        # A list of subprotocols specified by the connecting client
        # will be available in self.scope['subprotocols']
        await self.accept("subprotocol")
        # To reject the connection, call:
        await self.close()

    async def receive(self, text_data=None, bytes_data=None):
        # Called with either text_data or bytes_data for each frame
        # You can call:
        await self.send(text_data="Hello world!")
        # Or, to send a binary frame:
        await self.send(bytes_data="Hello world!")
        # Want to force-close the connection? Call:
        await self.close()
        # Or add a custom WebSocket error code!
        await self.close(code=4123)

    async def disconnect(self, close_code):
        # Called when the socket closes

Then on your asgi.py:

import os
import django
from channels.routing import ProtocolTypeRouter
from my_application.consumers import MyMqttConsumer
from django.core.asgi import get_asgi_application

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'integrator_mqtt.settings')

django.setup()

application = ProtocolTypeRouter({
        'http': get_asgi_application(),
        "websocket": MyConsumer.as_asgi(),
        'mqtt': MyMqttConsumer.as_asgi(),
    })

I would recommend to use daphne as the protocol server for the service that listens and streams to websockets.

Is it posible to listen to an MQTT server and publish with Websocket (endpoint) from our own server

1 Answers1