So Idea is behind setInterval and Sockets,
setInterval is supported in most browsers and javascript WbsocketApi is supported in almost everybrowser.
Brief overview:
setInterval() - this function behaviour is following when your computer is at sleep/suspended/hibernate mode it is paused and when you are at awaken mode it resumes itself.
The following code does the following, at first(maybe at the same time but) it starts php server_socket listening to the connections,
than javascript websocket api sends current timestamp in Unix timestamp milliseconds in every 2 seconds you can have 1 second it is up to you.
after that php server socket is getting this time and checks if it has anything like previous time to compare, when the code is first instantiated php does not has anything like previous time to compare it to the time which was sent from javascript websocket, so php does nothing but saves this time in the session called 'prev_time' and waits for another time data to be recieved from javascript socket, so here begins second cycle.
when php server socket new time data from javascript WebsocketApi it checks it has anything like previous time to compare to this newly received time data, it means that php checks if session called 'prev_time' exists, as we are in the second cycle php discovers that it exists, grabs it's value and does following $diff = $new_time - $prev_time, $diff will be 2 seconds or 2000 miliseconds because remember our setInterval cycle happens in every 2 seconds and time format we are sending is in miliseconds,
than php checks if($diff<3000) if difference is less than 3000 if it is it knows that user is active, again you can manipulate this seconds as you wish, I choose 3000 because possible latency in the network which is almost impossible but you know I am always cautious when it comes to networks, so let's continue, when php determines that user is active php just resets 'prev_time' session with the value of $new_time which was newly received and just for testing purposes it sends message back to javascript socket,
but if $diff is more than 3000 it means that something paused our setInterval and there is only way it can happen and I think you already know what I am saying, so in the else logic of ( if($diff<3000) ) you can logout user by destroying specific session and if you want to redirect you can send some text to javacript socket and create a logic which will execute window.location = "/login" depending on the text, that's it here is the code:
First it is index.html file just to load javascript:
<html>
<body>
<div id="printer"></div>
<script src="javascript_client_socket.js"></script>
</body>
</html>
then it is javascript it is not really beautifully coded but you can figure out READ COMMENTS THEY ARE IMPORTANT:
var socket = new WebSocket('ws://localhost:34237'); // connecting to socket
// Open the socket
socket.onopen = function(event) { // detecting when connection is established
setInterval(function(){ //seting interval for 2 seconds
var date = new Date(); //grabing current date
var nowtime = Date.parse(date); // parisng it in miliseconds
var msg = 'I am the client.'; //jsut testing message
// Send an initial message
socket.send(nowtime); //sending the time to php socket
},2000);
};
// Listen for messages
socket.onmessage = function(event) { //print text which will be sent by php socket
console.log('php: ' + event.data);
};
// Listen for socket closes
socket.onclose = function(event) {
console.log('Client notified socket has closed', event);
};
now here is part of php code, don't worry down there is full code too but this part is actually what does above mentioned jobs you will meet other functions too but they are for decoding and working with javascript sockets so it is actual thing right here READ COMMENTS THEY ARE IMPORTANT:
<?php
$decoded_data = unmask($data /* $data is actual data received from javascript socket */); //grabbing data and unmasking it | unmasking is for javascript sockets don't mind this
print("< ".$decoded_data."\n");
$response = strrev($decoded_data);
$jsTime = (int) $decoded_data; /* time sent by javascript in MILISECONDS IN UNIX FORMAT */
if (isset($_SESSION['prev_time'])) { /** check if we have stored previous time in the session */
$prev_time = (int) $_SESSION['prev_time']; /** grabbing the previous time from session */
$diff = $jsTime-$prev_time; /** getting the difference newly sent time and previous time by subtracting */
print("$jsTime - $prev_time = $diff"); /** printing the difference */
if($diff<3000){ /** checking if difference is less than 3 second if it is it means pc was not at sleep
*** you can manipulate and have for example 1 second = 1000ms */
socket_write($client,encode("You are active! your pc is awakend"));
$_SESSION['prev_time'] = $jsTime; /** saving newly sent time as previous time for future testing whcih will happen in two seconds in our case*/
}else { /** if it is more than 3 seconds it means that javascript setInterval function was paused and resumed after 3 seconds
** So it means that it was at sleep because when your PC is at sleep/suspended/hibernate mode setINterval gets pauesd */
socket_write($client,encode("You are not active! your pc is at sleep"));
$_SESSION['prev_time'] = $jsTime;
}
}else { /** if we have not saved the previous time in session save it */
$_SESSION['prev_time'] = $jsTime;
}
print_r($_SESSION);
?>
And here is the full code of php:
<?php
//Code by: Nabi KAZ <www.nabi.ir>
session_abort();
// set some variables
$host = "127.0.0.1";
$port = 34237;
date_default_timezone_set("UTC");
// don't timeout!
set_time_limit(0);
// create socket
$socket = socket_create(AF_INET, SOCK_STREAM, 0)or die("Could not create socket\n");
// bind socket to port
$result = socket_bind($socket, $host, $port)or die("Could not bind to socket\n");
// start listening for connections
$result = socket_listen($socket, 20)or die("Could not set up socket listener\n");
$flag_handshake = false;
$client = null;
do {
if (!$client) {
// accept incoming connections
// client another socket to handle communication
$client = socket_accept($socket)or die("Could not accept incoming connection\n");
}
$bytes = @socket_recv($client, $data, 2048, 0);
if ($flag_handshake == false) {
if ((int)$bytes == 0)
continue;
//print("Handshaking headers from client: ".$data."\n");
if (handshake($client, $data, $socket)) {
$flag_handshake = true;
}
}
elseif($flag_handshake == true) {
/*
**** Main section for detectin sleep or not **
*/
if ($data != "") {
$decoded_data = unmask($data /* $data is actual data received from javascript socket */); //grabbing data and unmasking it | unmasking is for javascript sockets don't mind this
print("< ".$decoded_data."\n");
$response = strrev($decoded_data);
$jsTime = (int) $decoded_data; /* time sent by javascript in MILISECONDS IN UNIX FORMAT */
if (isset($_SESSION['prev_time'])) { /** check if we have stored previous time in the session */
$prev_time = (int) $_SESSION['prev_time']; /** grabbing the previous time from session */
$diff = $jsTime-$prev_time; /** getting the difference newly sent time and previous time by subtracting */
print("$jsTime - $prev_time = $diff"); /** printing the difference */
if($diff<3000){ /** checking if difference is less than 3 second if it is it means pc was not at sleep
*** you can manipulate and have for example 1 second = 1000ms */
socket_write($client,encode("You are active! your pc is awakend"));
$_SESSION['prev_time'] = $jsTime; /** saving newly sent time as previous time for future testing whcih will happen in two seconds in our case*/
}else { /** if it is more than 3 seconds it means that javascript setInterval function was paused and resumed after 3 seconds
** So it means that it was at sleep because when your PC is at sleep/suspended/hibernate mode setINterval gets pauesd */
socket_write($client,encode("You are not active! your pc is at sleep"));
$_SESSION['prev_time'] = $jsTime;
}
}else { /** if we have not saved the previous time in session save it */
$_SESSION['prev_time'] = $jsTime;
}
print_r($_SESSION);
/*
**** end of Main section for detectin sleep or not **
*/
}
}
} while (true);
// close sockets
socket_close($client);
socket_close($socket);
$client = null;
$flag_handshake = false;
function handshake($client, $headers, $socket) {
if (preg_match("/Sec-WebSocket-Version: (.*)\r\n/", $headers, $match))
$version = $match[1];
else {
print("The client doesn't support WebSocket");
return false;
}
if ($version == 13) {
// Extract header variables
if (preg_match("/GET (.*) HTTP/", $headers, $match))
$root = $match[1];
if (preg_match("/Host: (.*)\r\n/", $headers, $match))
$host = $match[1];
if (preg_match("/Origin: (.*)\r\n/", $headers, $match))
$origin = $match[1];
if (preg_match("/Sec-WebSocket-Key: (.*)\r\n/", $headers, $match))
$key = $match[1];
$acceptKey = $key.'258EAFA5-E914-47DA-95CA-C5AB0DC85B11';
$acceptKey = base64_encode(sha1($acceptKey, true));
$upgrade = "HTTP/1.1 101 Switching Protocols\r\n".
"Upgrade: websocket\r\n".
"Connection: Upgrade\r\n".
"Sec-WebSocket-Accept: $acceptKey".
"\r\n\r\n";
socket_write($client, $upgrade);
return true;
} else {
print("WebSocket version 13 required (the client supports version {$version})");
return false;
}
}
function unmask($payload) {
$length = ord($payload[1]) & 127;
if ($length == 126) {
$masks = substr($payload, 4, 4);
$data = substr($payload, 8);
}
elseif($length == 127) {
$masks = substr($payload, 10, 4);
$data = substr($payload, 14);
}
else {
$masks = substr($payload, 2, 4);
$data = substr($payload, 6);
}
$text = '';
for ($i = 0; $i < strlen($data); ++$i) {
$text .= $data[$i] ^ $masks[$i % 4];
}
return $text;
}
function encode($text) {
// 0x1 text frame (FIN + opcode)
$b1 = 0x80 | (0x1 & 0x0f);
$length = strlen($text);
if ($length <= 125)
$header = pack('CC', $b1, $length);
elseif($length > 125 && $length < 65536)$header = pack('CCS', $b1, 126, $length);
elseif($length >= 65536)
$header = pack('CCN', $b1, 127, $length);
return $header.$text;
}
NOTE READ IT:
$new_time variable is $jsTime in Code
create folder and just copy and paste this in files run php socket with the command: php -f server_socket.php go to the localhost and test it open console to see messages it will say "you are active" or "you are not active"(when you come from sleep); your executin will happen when user will come from sleep not when they are at sleep cause at that moment everything is cached in pagefile(windows) or in swap(linux)
