index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Rate Update</title>
</head>
<body>
    <h1>Current rate: <span id="current-rate"></span></h1>
    <h2>Next rate: <span id="next-rate"></span></h2>

    <script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/4.1.2/socket.io.js"></script>
    <script>
        var socket = io.connect('http://' + document.domain + ':' + location.port);

        socket.on('connect', function() {
            console.log('Connected to server');
        });

        socket.on('update', function(data) {
            document.getElementById('current-rate').innerText = data.current_rate;
            document.getElementById('next-rate').innerText = data.next_rate;
        });
    </script>
</body>
</html>