https://www.egovframe.go.kr/wiki/doku.php?id=egovframework:com:cop:웹소켓메신저

https://velog.io/@ehddnr7355/9c55n853

https://velog.io/@hiy7030/chatting-1

https://velog.io/@hiy7030/chatting-2

https://wans1027.tistory.com/19