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README.md

Week 06: Intro to MQTT & Harper

Published: [Date TBD] • Duration: ~10-11 minutes • Difficulty: Beginner

📺 Watch On

  • YouTube — Primary platform
  • [Additional Platform] — Coming soon

Overview

This week we introduce MQTT and explore how Harper supports real-time messaging out of the box. You'll learn the fundamentals of MQTT, why it matters for modern applications, and how Harper's built-in capabilities make it easy to add pub/sub messaging to your projects without external dependencies.

Talk Track

[0:00-1:00] What is MQTT and Why It Matters

  • MQTT = OASIS standard messaging protocol for the Internet of Things (per mqtt.org)
  • Extremely lightweight publish/subscribe messaging transport
  • Designed for resource-constrained devices and unreliable networks
  • Small client footprint - runs on microcontrollers
  • Scales to millions of IoT devices
  • Common use cases: automotive, manufacturing, telecommunications, oil/gas, smart homes, AI Ops
  • Three QoS levels for reliability, TLS encryption, persistent sessions

[1:00-2:30] The Traditional MQTT Stack - Clients, Brokers, Topics

  • Reference: mqtt.org for complete architecture
  • Clients: Publishers (send messages) and Subscribers (receive messages)
    • Bidirectional communication - a client can be both publisher and subscriber
  • Brokers: Intermediaries that route messages between clients
    • Examples: Mosquitto, HiveMQ, EMQX
    • Manages connections, topic subscriptions, message delivery
  • Topics: Organize messages by category (like file paths: sensors/temperature/room1)
    • Subscribers filter what messages they receive based on topics
    • Decoupled architecture: publishers don't know who's subscribing
  • Traditional deployment: Separate broker + database + application logic = multiple services to coordinate

[2:30-4:00] Harper's Native MQTT Capabilities

  • Harper is a fully integrated microlith - all in a 100MB process:
    • Database (SQL + NoSQL)
    • Messaging (including MQTT broker)
    • Caching
    • Application hosting
  • MQTT broker is built-in - no external services needed
  • Acts as broker AND database simultaneously
  • Reference: https://docs.harperdb.io/docs/developers/real-time
  • Traditional stack: Multiple services, multiple failure points, multiple configs
  • Harper: One process, one config, one service to manage
  • Messages can be persisted to database - no glue code required

[4:00-5:00] Harper's MQTT Configuration

  • Review harperdb-config.yaml to show MQTT settings
  • MQTT is enabled by default in Harper
  • Default port: 1883 (standard MQTT port)
  • Show where MQTT broker configuration lives
  • No complex broker setup - just standard Harper config

[5:00-7:00] Demo Part 1: Publisher & Subscriber Without Message Retention

  • Connect MQTT Explorer (or similar client) to Harper localhost:1883
  • Open Harper Studio/UI to watch the database table in real-time
  • Publisher sends messages to topic: demo/test
  • Subscriber receives messages live
  • Messages flow through broker but are NOT retained
  • Show: No messages stored in Harper's table
  • This is standard MQTT behavior - messages are ephemeral

[7:00-9:00] Demo Part 2: Publisher & Subscriber WITH Message Retention

  • Enable message retention/persistence configuration
  • Publisher sends messages to topic: demo/sensor/temperature
  • Subscriber receives messages as before
  • Switch to Harper table view - messages ARE being stored!
  • Show: Each message appears in the Harper database table
  • Query the messages with SQL while publisher is still sending
  • Real-time messaging + automatic persistence
  • No glue code, no separate storage layer - it just works

[9:00-10:00] What Just Happened?

  • Harper acted as MQTT broker (handled pub/sub)
  • Harper simultaneously stored messages to database
  • Same topic hierarchy visible in both MQTT client and database
  • Query messages immediately with SQL or NoSQL APIs
  • One system, dual purpose: messaging + storage

[10:00-10:30] Wrap-up & Next Steps

  • What we learned: MQTT fundamentals and Harper's integrated approach
  • Benefits: simplified architecture, less infrastructure, automatic persistence

Key Learning Outcome

✓ Understand MQTT and Harper's Real-Time Messaging — Learn what MQTT is, why it's useful, and how Harper's built-in MQTT broker simplifies your architecture by combining messaging and database in one system.

Timestamps

Will be added after video is published

  • 00:00 — What is MQTT and Why It Matters
  • 01:00 — The Traditional MQTT Stack - Clients, Brokers, Topics
  • 02:30 — Harper's Native MQTT Capabilities
  • 04:00 — Harper's MQTT Configuration
  • 05:00 — Demo Part 1: Publisher & Subscriber Without Message Retention
  • 07:00 — Demo Part 2: Publisher & Subscriber WITH Message Retention
  • 09:00 — What Just Happened?
  • 10:00 — Wrap-up & Next Steps

Resources & Links

Documentation:

Community:

Tools Used:

  • Harper instance
  • MQTT Explorer (for testing)
  • Web browser

Prerequisites

  • Completion of Week 05
  • Harper instance running locally
  • Basic understanding of client-server architecture

Discussion & Feedback

Quick questions? Join the Discord for real-time help Episode feedback? Submit via GitHub Topic suggestions? Request a topic

Next Episode: Week 07 — MQTT in Harper - Real-Time Messaging

Subscribe on YouTube • Join the Discord