CoAP

CoAP - Constrained Application Protocol is a bit like REST but pared down to be as light as MQTT.   Like REST, it has GET/PUT/POST/DELETE.   CoAP is stateless (per connection) and sessionless, meaning data is sent and requested at any time, but without a connection state.   This allows CoAP to run on a transport like UDP, SMS, packet radio, or satellite where it is hard to get an immediate response.   You may

Adafruit CoAP tutorial

CoAP by DZone

escaped code goes here
https://www.freeformatter.com/html-escape.html