quick Java socket tutorial - https://www.youtube.com/watch?v=-xKgxqG411c
Java standards compliant WebSocket - https://www.pegaxchange.com/2018/01/28/websocket-server-java/
Kotlin crash course-https://www.youtube.com/watch?v=pXdY1B-KVJg
chat app in Kotlin - https://www.youtube.com/watch?v=g3ohGP4QJKY