CoAP is an IOT protocol. It stands for Constrained Application Protocol, defined by RFC7252. CoAP is a simple protocol with low overhead specifically designed for constrained devices( such as Microcontrollers) and constrained networks. This protocol is used in M2M data exchange and is very similar to HTTP.
CoAP is strictly speaking a session layer protocol. CoAP works on top of UDP(Transport Layer). CoAP architecture is divided into two sublayers: Messaging and Request/Response.
The task of detecting duplications is done by messaging sublayer and responsible for reliability while request-response sublayer is responsible for communication.
CoAP has four messaging modes:
Confirmable Message: It is a reliable message. In CoAP, a reliable message is obtained using a confirmable message CON. The client can be sure that the message will arrive at the server and send the acknowledgment to the first party. The ACK message contains the same ID of CON message.
Non Confirmable messages:
These messages don't require an acknowledgment from server. They are unreliable message do not contain critical information that must be delivered to the server. This category message contains the value read from sensors.
Piggyback Message: It is used from client/server direct communication where the server sends its response directly after receiving the message within the acknowledgment message.
Separate Mode: It is used when the server response comes in a message separate from acknowledgment, and may take some time to be sent by the server.
CoAP is strictly speaking a session layer protocol. CoAP works on top of UDP(Transport Layer). CoAP architecture is divided into two sublayers: Messaging and Request/Response.
The task of detecting duplications is done by messaging sublayer and responsible for reliability while request-response sublayer is responsible for communication.
CoAP has four messaging modes:
Confirmable Message: It is a reliable message. In CoAP, a reliable message is obtained using a confirmable message CON. The client can be sure that the message will arrive at the server and send the acknowledgment to the first party. The ACK message contains the same ID of CON message.
Non Confirmable messages:
These messages don't require an acknowledgment from server. They are unreliable message do not contain critical information that must be delivered to the server. This category message contains the value read from sensors.
Piggyback Message: It is used from client/server direct communication where the server sends its response directly after receiving the message within the acknowledgment message.
Separate Mode: It is used when the server response comes in a message separate from acknowledgment, and may take some time to be sent by the server.
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