how to use websockets?

please I need your help I'm creating an app and I want to send data through websockets but I do not know how to receive the data and create a page to send example: pagEnvia.html and I want to receive the data in my index.php I have this code that I got on the internet but I do not understand the reception of the message.

How do I do it?

<script type="text/javascript">

var ws;

      function initSocket(){

          ws = new WebSocket("wss://echo.websocket.org");
          ws.onopen = function(event){
            alert('Conexion Abierta');
            //ws.send('{"setID":"Realbingo90","passwd":"12345"}');
            setInterval(function(){
              ws.send("hola mundo");
            }, 1000);
          }

          ws.onmessage = function(event){
            console.log(event.data);
          }

          ws.onclose= function(){
             alert('Cerrado');
          }
      }

    initSocket();

I need your prompt help.