How does a ws websocket tell if connection event corresponds to an existing client in the clients list? - node.js

Question

I am using the ws module to implement a WebSocket server in NodeJS. On the client-side, I request the connection using
webSocket = new WebSocket(url);
On the server-side, I have code that handles the 'connect' event, in which I print out the number of clients using
console.log("Total number of clients = " + wsServer.clients.size);
If I open the client-side in different tabs (or browsers), the number of clients is incremented for each new connection (as expected).
If I refresh a page, the webSocket = new WebSocket(url); code is called again and on the server the code handling the 'connect' event (see below) is also called again. However, in this case, the number of clients is not incremented. This is nice behaviour as it maintains the number of connections one wants, but I cannot see how this is done. I want to be able to test if this is an existing connection as I have a chat room running that says 'so-and-so' has joined when a new connection is made. However, I don't want this to happen every time a user refreshes their page.
Here is the server-side event-handler:
// On connection
wsServer.on("connection", function (ws, req) {
let { query } = url.parse(req.url, true);
ws.userName = ("name" in query) ? query.name : null;
ws.roomCode = ("roomCode" in query) ? query.roomCode : null;
ws.userPIN = ("PIN" in query) ? query.PIN : null;
console.log(ws.userName + " joined room " + ws.roomCode);
console.log("Total number of clients = " + wsServer.clients.size);
let data = {
userName: "Server",
message: ws.userName + " joined the room."
};
let dataStr = JSON.stringify(data);
// Loop through each client
wsServer.clients.forEach((client) => {
// Check if client is ready and in same room
if ((client.readyState === WebSocket.OPEN) && (client.roomCode == ws.roomCode)) {
client.send(dataStr);
}
});
// On message event
ws.on("message", function (msg) {
// Loop through each client
wsServer.clients.forEach((client) => {
// Check if client is ready and in same room
if ((client.readyState === WebSocket.OPEN) && (client.roomCode == ws.roomCode)) {
client.send(msg.toString());
}
});
});
});
As one can see, I do modify the client by adding name and room code fields to it but these are not present when the 'connect' event fires, implying the object is being created from scratch. However, no extra client is being added to the clients list, so what I would like to understand is:
how does the ws package know this is an existing connection?
how can I test for this?
Any advice would be gratefully received!

Answer 1

On investigation, it turns out the when the user refreshes the page, the WebSocket connection is closed and then re-opened. Hence there is no testing for an existing client, the existing client is just deleted on the server and the new connection added - hence the number of clients does not appear to change.