Q: What is the difference between MQTT MQTT-SN and CoAP protocols for IoT?
Answer
MQTT (MQ Telemetry Transport): TCP-based pub/sub protocol. Excellent for reliable always-connected devices. Overhead ~2 bytes header. Best for: gateways cloud-connected sensors. QoS 0 (at most once) QoS 1 (at least once) QoS 2 (exactly once). MQTT-SN: designed for sensor networks with UDP support and shorter message IDs – works over Zigbee/Sigfox. Best for: battery-powered devices on non-TCP networks. CoAP (Constrained Application Protocol): RESTful UDP-based protocol. Uses DTLS for security. Best for: devices that need request/response (HTTP-like) on unreliable networks with very low power. Choose MQTT for cloud-to-device with reliable connection; CoAP for devices that sleep frequently on unreliable networks; MQTT-SN for non-IP sensor networks.
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