The correct answer is: B. CoAP
CoAP is a lightweight, application layer protocol for constrained devices and low-bandwidth networks. It is designed to be an alternative to HTTP for machine-to-machine (M2M) and Internet of Things (IoT) applications. CoAP is an application layer protocol that runs on top of User Datagram Protocol (UDP). UDP is a connectionless protocol, which means that it does not establish a connection between the sender and receiver before sending data. This makes UDP more efficient than connection-oriented protocols like TCP, but it also means that there is no guarantee that the data will be delivered. CoAP uses a request-response model, where the client sends a request to the server, and the server sends a response. CoAP messages are small, typically 8 to 12 bytes in size. This makes CoAP well-suited for constrained devices with limited resources.
The other options are incorrect because:
- HTTP is a connection-oriented protocol that runs on top of TCP.
- TCP is a connection-oriented protocol that provides reliable, ordered, and error-checked delivery of data.
- MQTT is a publish/subscribe messaging protocol that runs on top of TCP.