README.md

Dash with MQTT

dash_mqtt is a Dash component library for adding MQTT messaging functionality to your Dash apps. It is essentially a wrapper around MQTT.js.

Usage

Simple echo example using emqx.io test MQTT broker.

import dash_mqtt
import dash
from dash.dependencies import Input, Output, State
import dash_html_components as html
import dash_core_components as dcc

TEST_SERVER = 'broker.emqx.io'
TEST_SERVER_PORT = 8083
TEST_SERVER_PATH = 'mqtt'
MESSAGE_OUT_TOPIC = 'testtopic'
MESSAGE_IN_TOPIC = 'testtopic'

app = dash.Dash(__name__)

app.layout = html.Div([
    dash_mqtt.DashMqtt(
        id='mqtt',
        broker_url=TEST_SERVER,
        broker_port = TEST_SERVER_PORT,
        broker_path = TEST_SERVER_PATH,
        topics=[MESSAGE_IN_TOPIC]
    ),
    html.H1('MQTT echo'),
    html.P('MQTT echo server to ' + TEST_SERVER + ' on port ' + str(TEST_SERVER_PORT)),
    dcc.Input(
        id='message_to_send',
        placeholder='message to send',
        debounce = True),
    html.Button('Send',id='send'),
    html.Div(id='return_message')
])


@app.callback(
        Output('mqtt', 'message'),
        Input('send', 'n_clicks'),
        State('message_to_send', 'value')
    )
def display_output(n_clicks, message_payload):
    if n_clicks:
        return {
            'topic': MESSAGE_OUT_TOPIC,
            'payload' : message_payload
        }
    return dash.no_update

NOTE

MQTT.js is running as an MQTT client in the browser in this implementation (As a React component as per typical Dash components). Subsequently, from here:

1. There is no way for JavaScript running in browsers to open TCP sockets so "normal" MQTT is impossible in browser apps.
2. To get around this limitation, MQTT.js uses MQTT over WebSockets instead when it detects it's running in a browser.

This means that you need to set the broker_port up to point at the MQTT-over-WebSockets port of the MQTT broker you are using, or if you are setting up your own broker server, turn on MQTT-over-WebSockets and expose a port.

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Help with developing the component

If you are want to adapt or help develop the component, refer README_DEV.md

Currently written to suit author's needs - MQTT broker running in a DOcker Container on a local network for home IOT scenarion using IOTStack, so have not put any effort into encrypted messaging.