It enables those constrained devices called "nodes" to communicate with the wider Internet using similar protocols.
CoAP is an application-layer protocol that is intended for use in resource-constrained Internet devices, such as wireless sensor network nodes.
CoAP is designed to easily translate to HTTP for simplified integration with the web, while also meeting specialized requirements such as multicast support, very low overhead, and simplicity.
Various extensions have been proposed, particularly: CoAP makes use of two message types, requests and responses, using a simple, binary header format.
CoAP is by default bound to UDP and optionally to DTLS, providing a high level of communications security.
When used with 6LoWPAN as defined in RFC 4944, messages should fit into a single IEEE 802.15.4 frame to minimize fragmentation.
You can find the latest CoAP request/response codes at [1], though the below list gives some examples: Every request carries a token (but it may be zero length) whose value was generated by the client.
The use of multicast has certain benefits such as reducing the number of packets needed to deliver the request to the members.