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MQTT Explorer

MQTT Explorer is a graphical MQTT client for desktop and browser. It allows you to monitor, analyze, and debug MQTT messages.

Installation

Add the following template to your docker-compose.yml and then run ei23 dc.

Mosquitto Required

MQTT Explorer requires an MQTT broker. By default, Mosquitto is installed with the ei23 script.

Template

  mqtt-explorer:
    image: sapk/mqtt-explorer
    container_name: mqtt-explorer
    restart: unless-stopped
    ports:
      - "4004:4004"

First Start

  1. After startup, you can access MQTT Explorer at http://[IP]:4004
  2. Click on + to create a new connection
  3. Enter the IP address of your MQTT broker (e.g., mosquitto or 192.168.1.x)
  4. Default port: 1883

Configure Connection

Field Value
Host mosquitto (Docker) or IP address
Port 1883
Username Your MQTT username
Password Your MQTT password

Features

  • Real-time Monitoring - See all MQTT messages live
  • Topic Tree - Clear hierarchy of all topics
  • Send Messages - Manually publish messages
  • Statistics - Message history and graphs
  • Filter - Search for topics and messages
  • Export - Export messages as JSON

MQTT with Home Assistant

Home Assistant uses MQTT for many integrations:

Example Topics

Topic Description
homeassistant/# Home Assistant Discovery
zigbee2mqtt/# Zigbee2MQTT Devices
rtl_433/# 433MHz Sensors
esphome/# ESPHome Devices

Home Assistant Discovery

ESPHome and Zigbee2MQTT use Home Assistant Discovery:

# Automatically configured devices appear under:
homeassistant/sensor/[device_name]/config

MQTT with ESPHome

ESPHome communicates by default via the Home Assistant API, but can also use MQTT:

mqtt:
  broker: 192.168.1.x
  username: mqtt_user
  password: !secret mqtt_password

Debugging with MQTT Explorer

How to find MQTT issues:

  1. Open MQTT Explorer
  2. Filter by the relevant topic
  3. Check if messages are being sent/received
  4. Analyze the message structure
  5. Test sending messages manually

Notes

  • The port is 4004 by default
  • MQTT Explorer is also available as a desktop app
  • Ideal for troubleshooting MQTT problems
  • Can also be used for Node-RED debugging

Further Information