Web Page update without polling

Question

I\'m developing a web app where a user can request a service and a provider will be available to respond to him. So, When a user requests for some sort of service, our appli

Answer 1

here is a simple Server Sent Event Script using php.

support

https://developer.mozilla.org/en-US/docs/Web/API/EventSource

js

var sse=new EventSource("sse.php");
sse.onmessage=function(e){
 document.body.innerHTML=e.data;
};

sse.php

header('Content-Type: text/event-stream'); // specific sse mimetype
header('Cache-Control: no-cache'); // no cache
while(true) {
 if(/*something changes*/){
  echo "id: ".time().PHP_EOL;
  echo "data: ".$data.PHP_EOL;
  echo PHP_EOL;
 }
  ob_flush(); // clear memory
  flush(); // clear memory
  sleep(10);// seconds 
}

this keeps the connection open with the client,

then it checks if something is changed ... db/file whatever

outputs the data if changed

and then clears the php cache

waits 10 seconds and does it again.

---

As you can see the client recieves the data only if something changes on the server

but i totally don't know how the server could handle 1000's of people.

---

node.js would be a better way. but it depends what languages you are using and/or if you can actually use node.js.

websockets is both ways.

server sent event is oneway.(you need this)

EDIT

more data inside the sse response:

js

var sse=new EventSource("sse.php");
sse.onmessage=function(e){
 console.log(JSON.parse(e.data))
};

sse.php

header('Content-Type: text/event-stream'); // specific sse mimetype
header('Cache-Control: no-cache'); // no cache
while(true) {
 if(/*something changes*/){
  echo "id: ".time().PHP_EOL;

  $dataArray=array('id'=>$id,'name'=>$name,'more'=>$more);
  echo "data: ".json_encode($dataArray).PHP_EOL;

  echo PHP_EOL;

 }
  ob_flush(); // clear memory
  flush(); // clear memory
  sleep(10);// seconds 
}

if you need some more info just ask