https://midnightcow.tistory.com/36
https://github.com/mqttjs/MQTT.js#example
https://yonghyunlee.gitlab.io/node/node-mqtt/
http://www.hardcopyworld.com/ngine/aduino/index.php/archives/3369
https://github.com/moscajs/mosca
http://charlie0301.blogspot.com/2018/04/socketio-mqtt.html
CoAP는 RESTFUL 지원은 하는데, 1:1프로토콜이며 pub/sub가 불가하다.
https://m.blog.naver.com/renucs/220635745908
잘나옴. 심화과정. 비교
http://www.hellot.net/new_hellot/magazine/magazine_read.html?code=205&sub=002&idx=27478
https://blog.naver.com/yujury76/221565107415
https://www.joinc.co.kr/w/man/12/MQTT#panel2