using the begin method, and then give it a callback function that is executed when the ESP receives a WebSocket message.
   </div>
   <h4>Server handlers</h4>
   <div>
        This is the code that is executed on certain server-related events, like when an HTTP request is received, when a file is being uploaded, when there's an incoming WebSocket message ... etc. 
   </div>
   <div>
       <pre><code><span style="color: #00979c;">void</span> <span style="color: #000000;">handleNotFound</span><span style="co