Constrained Application Protocol is a protocol intended to be used in very simple low power resource-constrained electronic devices to communicate and to be controlled remotely over the Internet. CoAP is an application layer protocol run on most devices that support UDP or a UDP analogue and designed to easily translate to HTTP for integration with the web while meeting requirements such as multicast support, very low overhead, and simplicity for both IOT and M2M.
IETF Constrained RESTful environments (CoRE) Working Group has done the major standardization work for CoAP with the following features: Overhead and parsing complexity; URI and content type support; Support for the discovery of resources provided by known CoAP services; Simple subscription for a resource, and resulting push notifications. CoAP makes use of two message types, requests and responses, using a simple binary base header format. CoAP is by default bound to UDP and optionally to DTLS, providing a high level of communications security.
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