The Constrained Application Protocol (COAP) is a user-server based protocol. With the help of this protocol, the COAP package is shared between various client nodes, which are directed by the COAP server. This server is in charge of sharing the details contingent on its logic but has not to recognize. COAP is used with the requisition, which helps state transfer miniature. Unlike MQTT, it is not systemized.
MQTT stands for Message Query Telemetry Protocol. It is a communication-based protocol. Also, it is used in IoT devices. MQTT is established on the publish-subscribe procedure in which clients get the details through a broker only to the consent subject. A broker is a negotiator who classifies messages which are mainly 'labels' before being conveyed.
MQTT does not help in labelling messages with types or another schema to help clients understand them. Notifications are used for various purposes, but all clients should realize messages appear up-front to let communication. COAP contrarily give default help for content debate. And find out the allowing devices to investigate each other to find ways of interchanging data.
The following table highlights the major differences between COAP and MQTT protocols −
|COAP stands for Constrained Application Protocol.||MQTT stands for Message query telemetry transport.|
|For communication, it uses a request-response prototype.||For communication, it uses the publish-subscribe prototype.|
|It uses asynchronous and synchronous messaging.||It uses only asynchronous mode for messaging.|
|It uses User Datagram Protocol (UDP).||It uses the Transmission Control Protocol (TCP).|
|The Heather size of CAOP is 4 bytes.||The Heather size of MQTT is 2 bytes.|
|It is RESTful based.||It is not RESTful based.|
|It does not have persistence support.||It is mainly used for live communication and has persistence support.|
|It will give labels to the messages.||It does not have any such function.|
|It has a secured system, and its usability is in Utility area networks.||It is very secure, and its usability is in IoT applications.|
|It has Low Latency and NAT issues.||It has Low Latency and NAT issues.|
Are Open Standards
Are better for unnatural environments than HTTP
Give contraption for asynchronous communication
Have an area of execution
Various other protocols are also used for IoT applications like AMQP, XMPP. DDS or LwM2M. Before choosing a protocol, one should have the knowledge of business requirements, realization of the benefits and demerits of the protocols provided by the market, and the capability to choose the one that best suits a given base case.