IoT Protocols (MQTT, CoAP)

📡 IoT Protocols: MQTT & CoAP

1. MQTT (Message Queuing Telemetry Transport)

• Type: Publish/Subscribe messaging protocol

• Designed for: Lightweight, low-bandwidth, unreliable networks

• How it works:

  • Devices (clients) publish messages to a broker on specific topics.

  • Other devices subscribe to those topics to receive messages.

• Use Cases:

  • Remote sensor monitoring

  • Home automation

  • Industrial IoT

• Advantages:

  • Minimal overhead, ideal for constrained devices

  • Reliable message delivery with QoS levels (0,1,2)

  • Supports retained messages and last will/testament features

• Port: Usually runs over TCP/IP on port 1883 (unencrypted) or 8883 (TLS encrypted)

---

2. CoAP (Constrained Application Protocol)

• Type: Client-server protocol modeled on HTTP, but optimized for IoT

• Designed for: Simple devices and constrained networks (low power, lossy)

• How it works:

  • Uses RESTful architecture — devices send requests (GET, POST, PUT, DELETE) to servers.

  • Supports multicast requests and asynchronous message exchange.

• Use Cases:

  • Smart lighting

  • Building automation

  • Sensor networks

• Advantages:

  • Very low overhead, runs over UDP (faster, lighter than TCP)

  • Supports resource discovery and proxying

  • Easily integrates with HTTP systems via proxies

• Port: Default UDP port 5683, secured by DTLS (Datagram Transport Layer Security)

---

🔑 Summary Comparison

Feature	MQTT	CoAP
Protocol Model	Publish/Subscribe	Request/Response (RESTful)
Transport Layer	TCP	UDP
Use Case Focus	Messaging for telemetry and control	Resource manipulation in constrained environments
Security	TLS	DTLS
Overhead	Low, but higher than CoAP	Very low
Communication	Asynchronous, broker-based	Synchronous, direct client-server