IoT

Protocol Selection

• MQTT for lightweight messaging — pub/sub, low bandwidth, ideal for sensors
• CoAP for constrained devices — UDP-based, REST-like, very low power
• HTTP/REST for capable devices — familiar but heavier, use when bandwidth allows
• WebSocket for real-time bidirectional — dashboards, live updates
• Zigbee/Z-Wave for mesh networks — no WiFi needed, battery-friendly

MQTT Essentials

• Broker is the central hub — Mosquitto most common self-hosted
• Topics are hierarchical — home/livingroom/temperature
• QoS levels: 0 (fire-forget), 1 (at least once), 2 (exactly once)
• Retain flag keeps last message — new subscribers get current state
• Will message announces disconnection — device offline detection