Difference between COAP and MQTT Protocols

Constrained Application Protocol is an application layer protocol that was introduced by the Internet Engineering Task Force in the year 2014. CoAP is designed for the constrained environment. It is a web-based protocol that resembles HTTP. Message Queuing Telemetry Transport is a communications protocol designed for Internet of Things devices with extremely high latency and restricted low bandwidth. Message Queuing Telemetry Transport is a perfect protocol for machine-to-machine (M2M) communication since it is designed specifically for low-bandwidth, high-latency settings.

What is a Constrained Application Protocol?

The constrained application protocol is client-server-based. With this protocol, the COAP packet can be shared between different client nodes which are commanded by the COAP server. The server is responsible for sharing the information depending on its logic but has not acknowledged it. This is used with the applications which support the state transfer model. 

Characteristics of COAP

• UDP-Based: CoAP uses UDP (User Datagram Protocol) instead of TCP, making it suitable for limited resources and networks.
• HTTP-Like Semantics: CoAP employs HTTP-like methods (GET, POST, PUT, DELETE) for interactions.
• Multicast Support: CoAP includes UDP’s multicast feature, which TCP lacks.
• Low Overhead: CoAP minimizes protocol overhead for efficient communication in constrained environments

What is Message Queuing Telemetry Transport?

Message Queuing Telemetry Transport is a communication-based protocol used for IoT devices. MQTT is a simple, lightweight messaging protocol used to establish communication between multiple devices. It is a TCP-based protocol relying on the publish-subscribe model. This communication protocol is suitable for transmitting data between resource-constrained devices having low bandwidth and low power requirements. Hence this messaging protocol is widely used for communication in the IoT Framework.

Characterstics of MQTT

• Publish-Subscribe Model: MQTT operates on a publish-subscribe model, where publishers send messages to topics, and subscribers receive those messages.
• Lightweight: MQTT minimizes data packet size, making it ideal for bandwidth-constrained environments.
• Retained Messages: MQTT allows retaining the most recent message for a topic.
• Last Will and Testament: If a client disconnects abruptly, a pre-defined “last will” message is sent to subscribers.
• Session Management: MQTT supports re-establishing sessions after connection loss

Difference between COAP and MQTT protocols

Conclusion

CoAP and MQTT are both application layer protocols built for IoT environments, although they address different requirements. CoAP is suited for confined situations due to its request-response mechanism over UDP, making it suitable for applications with limited bandwidth and power. MQTT, on the other hand, is built for dependable, low-bandwidth communication using TCP’s publish-subscribe paradigm, making it ideal for M2M communication within IoT frameworks.