Kotlin Blueprints

Emitting the event

The Socket.IO library works on a simple principle—emit and listen. Clients emit the messages and a listener listens to those messages and performs an action associated with them. 

So now, whenever a user successfully logs in, we will emit an event named add_user and the server will add it to an online user's list.

The following code line emits the message:

    socket.emit("add_user", it)

The following code snippet listens to the message and adds a user to the list:

    socket.on("add_user", { nickName ->     socket.nickname= nickName     numOfUsers = numOfUsers.inc()     usersList.add(nickName as String)    })

The socket.on function will listen to the add_user event and store the nickname in the socket.