index-ws.js

const express = require("express");
const server = require("http").createServer();
const app = express();

app.get("/", function(req, res) {
    res.sendFile("index.html", {root: __dirname});
});

server.on("request", app);
server.listen(3000, function() {console.log("server started on port 3000")});

process.on('SIGINT', () => {
    wss.clients.forEach(function each(client) {
        client.close();
    });
    server.close(() => {
        shutdownDB();
    })
})

/** Begin Websocket */
const WebsocketServer = require("ws").Server;

const wss = new WebsocketServer({server: server});

wss.on("connection", function connection(ws) {
    const numClients = wss.clients.size;
    console.log(`Clients connected`, numClients);

    wss.broadcast(`Current visitors: ${numClients}`);

    if(ws.readyState === ws.OPEN) {
        ws.send("Welcome to my server");
    }

    db.run(`INSERT INTO visitors (count, time)
        VALUES (${numClients}, datetime('now'))
    `);
    ws.on('close', function close() {
        const numClients = wss.clients.size;
        wss.broadcast(`Current visitors: ${numClients}`);
        console.log("Client has disconnected");
    });
});

wss.broadcast = function broadcast(data) {
    wss.clients.forEach(function each(client) {
        client.send(data);
    });
}

/** End Websockets */
/** Begin Database */
const sqlite = require("sqlite3");
const db = new sqlite.Database(':memory:');

db.serialize(() => {
    db.run(`
        CREATE TABLE visitors (
            count INTEGER,
            time TEXT
        )
    `)
});

function getCounts() {
    db.each("SELECT * FROM visitors", (err, row) => {
        console.log(row);
    })
}

function shutdownDB() {
    getCounts();
    console.log("Shutting Down DB");
    db.close();
}