Connection from a web app to a Processing sketch through websockets

index.html

<script>
    // Create a connection to the server
    var ws = new WebSocket('ws://172.18.246.234:8080/p5websocket');

    // As soon as the connection is established, send a "Ping" message to the server
    ws.onopen = function() {
        ws.send('Ping');
    };

    // Whenever we receive a message from the server, display it in a popup
    ws.onmessage = function(e) {
        alert(e.data);
    };
</script>

sketch.pde

WebSocketP5 socket;

void setup() {
  // Setup the socket that listens for incoming connections
  socket = new WebSocketP5(this, 8080);
}

void draw() {
}

void stop() {
  // When the processing sketch stops, kill the server
  socket.stop();
}

void websocketOnMessage(WebSocketConnection con, String msg) {
  // Whenever we receive a message from one of the phones, this code will be executed
  println(msg);
}

void mousePressed() {
  // Send a "Pong" message to all connected phones
  socket.broadcast("Pong");
}