How to stop Server-Sent Events

Question

Hello I have a javascript code that listens to a PHP code via Server-Sent Events, it is working well the response is sent from the server trough a loop and when the loop ends the Server-Sent Events stops however a few seconds after the script is again listening. how can I end the Server-Sent Events when the loop from the server side ends too? Thanks.

JS :

var sse=new EventSource("data.php");
            sse.onmessage=function(event){
                document.getElementById("map").innerHTML+=event.data;              
            };

PHP:

<?php
header('Content-Type: text/event-stream'); //indicates that server is aware of server sent events
header('Cache-Control: no-cache');//disable caching of response

$coordinates = [  
   [  
      "20:11",
      33.5731235,
      -7.6433045
   ],
   [  
      "20:11",
      33.5731054,
      -7.6432876
   ],
   [  
      "20:11",
      33.5731644,
      -7.6433304
   ]
];

foreach($coordinates as $c){  
  echo "data: ".json_encode($c)."\n\n";
  ob_get_flush();
  flush();
  sleep(1);
}

Answer 1

You could use a boolean variable isOpenOnce = false in your javascript and then in your sse.onopen set isOpen to true the first time. In the beginning check the flag and close connection if true. This way no need of server side changes.

var isOpenOnce = false;
sse.onopen = function() {
 if(isOpenOnce) {
  sse.close();
 }else {
  console.log("Connection to server opened.");
  isOpenOnce = true;
 }
}