Android MQTT Client App

A lightweight mobile MQTT client for Android. Useful if you want to:

• explore and learn how the MQTT protocol works
• debug and test existing MQTT infrastructure
• have a simple communication with IoT devices

For testing, pair the app with the HiveMQ WebSocket client.

1. Getting started

1.1 Run the app

1. Make sure the device or emulator has internet access.
2. Run the app and connect to a broker — use the Default broker option to connect to the HiveMQ public broker instantly.
3. Subscribe to a topic — testtopic/# is offered as a default.
4. Publish custom messages and watch incoming messages arrive.

1.2 Test against a counterpart

1. Open the HiveMQ WebSocket client.
2. Set up a simple test client and exchange messages with the app.

2. Features

Core

• Connect to an MQTT broker
• Subscribe to topics
• Publish custom messages
• Receive and monitor incoming messages live

Quality of life

• Bookmark recent brokers for one-tap reconnect
• Bookmark previously subscribed topics for quick reuse
• "Scroll to top" button on the received-messages list
• MQTT errors surfaced via Snackbars

3. Tech stack

• Language: Kotlin (JDK 17)
• UI: Jetpack Compose + Material 3, single-Activity with Navigation-Compose
• Architecture: MVVM — ViewModels + StateFlow, layered data / domain / ui
• DI: Koin
• Persistence: Room (recent brokers, subscribed topics)
• MQTT: HiveMQ MQTT client
• SDK: min 24, target 36

4. Screenshots