j4flmao IoT Protocols: MQTT and CoAP
MQTT is a lightweight publish-subscribe protocol running over TCP/IP. It defines three Quality of Service (QoS) levels: QoS 0 (at most once), QoS 1 (at least once, requiring a PUBACK), and QoS 2 (exactly once, using a four-step handshake).
CoAP (Constrained Application Protocol) is designed for UDP-based networks. It maps HTTP semantics to a compact binary format, utilizing a fixed 4-byte header. CoAP supports request/response patterns and multicast, making it suitable for lossy networks (LLNs) where TCP overhead is prohibitive.
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flowchart TD
subgraph PubPublisher ["Publisher<br><br><br>"]
A[Sensor] -->|"Publish(QoS1)"| B[MQTT Broker]
end
subgraph SubSubscriber ["Subscriber<br><br><br>"]
B -->|"Deliver()"| C[Backend Service]
C -->|"PUBACK()"| B
end