How can I check in real time if a user is logged in?

Question

I am building a simple support chat for my website using Ajax. I would like to check if the user that I am currently chatting with left the browser.

At the moment I have build in that feature by setting interval function at customer side that creates the file with name: userId.txt

In the admin area I have created an interval function that checks if userId.txt exists. If it exists, it deletes it. If the file is not recreated by the custom interval function - next time the admin function will find out that file is not there it mark customer with this userId as inactive.

Abstract representation:

customer -> interval Ajax function -> php [if no file - create a new file]
admin -> interval Ajax function -> php [if file exists - delete the file] -> return state to Ajax function and do something

I was wondering if there is any better way to implement this feature that you can think of?

Why are you checking against a file?? I would be saving the last date of the user activity, example mouse move into a DB. And checking against that in the other side. — Gonz, Sep 16 '15 at 03:29
The thing is that I am not sure which one would be more resource consuming. I was hoping that someone have some experience with this kind of things. Btw this project works on log files (text files) instead of DB. But I can consider moving it to DB if someone gives me a good reason for that. I am open to sugestions. — DevWL, Sep 16 '15 at 03:37
checkout this `http://php.net/manual/en/function.ignore-user-abort.php` — Payer Ahammed, Oct 05 '15 at 16:33
You can set cookies in PHP and then reference the cookies in PHP if you want to know if they are logged in. — www139, Oct 08 '15 at 23:37

Pedro Lobito · Accepted Answer · 2015-10-08T17:44:24.117

My solution is to use the jquery ready and beforeunload methods to trigger an ajax post request that will notify when the user arrives and leaves. This solution is "light" because it only logs twice per user.

support.html

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script>

//log user that just arrived - Page loaded
$(document).ready(function() {
         $.ajax({
        type: 'POST',
        url: 'log.php',
        async:false,
        data: {userlog:"userid arrived"}
    });
});

//log user that is about to leave - window/tab will be closed.
$(window).bind('beforeunload', function(){
    $.ajax({
        type: 'POST',
        url: 'log.php',
        async:false,
        data: {userlog:"userid left"}
    });
});
</script>
</head>
<body>

<h2>Your support html code...</h2>

</body>
</html>

log.php

<?php

//code this script in a way that you get notified in real time
//in this case, I just log to a txt file

$userLog = $_POST['userlog'];
file_put_contents("userlog.txt", $userLog."\n", FILE_APPEND );
//userid arrived
//userid left

Notes:

1 - Tested on Chrome, FF and Opera. I don't have a mac so I couldn't test it on Safari but it should work too.
2 - I've tried the unload method but it wasn't as reliable as beforeunload.
3 - Setting async to false on the ajax request means that the statement you are calling has to complete before the next statement, this ensures that you'll get notified before the window/tab is closed.

There are cases where this does not work. Namely, if the user puts their computer to sleep or performs another similar action that does not actually close the browser window or navigate away. — kevin.groat, Oct 08 '15 at 19:47
Sure, you're right but solutions that check if a user is still "alive" in real-time require a fair amount of server/network resources. Ping can, sometimes, provide this information but in most cases isn't reliable. — Pedro Lobito, Oct 08 '15 at 19:54
I'm very late at this problem but this is not working when user directly closes the tab . On page refresh and navigating backwards this is fine. please help. — Anurag Shukla, Jun 10 '21 at 01:51

score 5 · Answer 2 · answered Sep 16 '15 at 03:51

5

@Gonzalon makes a good point but using a normal DB table or the filesystem for constantly updating user movement would be exhaustive to most hard disks. This would be a good reason for using shared memory functions in PHP.

answered Sep 16 '15 at 03:51

Devon Bessemer

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score 5 · Answer 3 · edited May 23 '17 at 12:22

You have to differentiate a bit between the original question "How do i check in real-time, if a user is logged in?" and "How can i make sure, if a user is still on the other side (in my chat)?".

For a "login system" i would suggest to work with PHP sessions.

For the "is user still there" question, i would suggest to update one field of the active session named LAST_ACTIVITY. It is necessary to write a timestamp with the last contact with the client into a store (database) and test whether that is older than X seconds.

I'm suggesting sessions, because you have not mentioned them in your question and it looks like you are creating the userID.txt file manually on each Ajax request, right? Thats not needed, unless working cookie and session-less is a development requirement.

Now, for the PHP sessions i would simply change the session handler (backend) to whatever scales for you and what makes requesting information easy. By default PHP uses the session temp folder to create session files, but you might change it, so that the underlying session handler becomes a mariadb database or memcache or rediska.

When the users sessions are stored into a database you can query them: "How many users are now logged in?", "Who is where?".

The answer for "How can I check in real time if a user is logged in?" is, when the user session is created and the user is successfully authenticated.

For real-time chat application there are a lot of technologies out there, from "php comet", "html5 eventsource" + "websockets" / "long polling" to "message queues", like RabbitMq/ActiveMq with publish/subscribe to specific channels.

If this is a simple or restricted environment, maybe a VPS, then you can still stick to your solution of intervalic Ajax requests. Each request might then update $_SESSION['LAST_ACTIVITY'] with a server-side timestamp. Referencing: https://stackoverflow.com/a/1270960/1163786

A modification to this idea would be to stop doing Ajax requests, when the mouse movement stops. If the user doesn't move the mouse on your page for say 10 minutes, you would stop updating the LAST_ACTIVITY timestamp. This would fix the problem of showing users who are idle as being online.

Another modification is to reduce the size of the "iam still here" REQUEST to the server by using small GET or HEADER requests. A short HEADER "ping" is often enough, instead of sending long messages or JSON via POST.

You might find a complete "How to create an Ajax Web Chat with PHP, jQuery" over here. They use a timeout of 15 seconds for the chat.

score 4 · Answer 4 · answered Sep 16 '15 at 03:58

You can do it this way, but it'll be slow, inefficient, and probably highly insecure. Using a database would be a noticeable improvement, but even that wouldn't be particularly scalable, depending on how "real-time" you want this to be and how many conversations you want it to be able to handle simultaneously.

You'd be much better off using a NoSQL solution such as Redis for any actions that you'll need to run frequently (ie: "is user online" checks, storing short-term conversation updates, and checking for conversation updates at short intervals).

Then you'd use the database for more long-term tasks like storing user information and saving active conversations at regular intervals (maybe once per minute, for example).

Quite interesting aproach I will have to investygate it a litle bit more with comparison to my curent aproach in terms of resources and speed. Thx — DevWL, Sep 16 '15 at 13:19

score 4 · Answer 5 · answered Oct 03 '15 at 09:07

4

Why Ajax and not Websockets? Surely a websocket would give you a considerably faster chat system, wouldn't require generating and checking a text file, would not involve a database lookup and you can tell instantly if the connection is dropped.

answered Oct 03 '15 at 09:07

Professor Abronsius

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Chat aplication most of the time will be redistributed with websites that are often hosted by the clients on share hosting which usually do not allow for websockets to function. For example share hosting tend often to limit websockets to listen with gaps about 30 seckounds, or simply not allow websockets at all. If the chat would be build only for VPS that would not be an issue for sure. Thanks for your contribiution. – DevWL Oct 05 '15 at 08:30

score 4 · Answer 6 · answered Oct 08 '15 at 16:32

I would install the https://github.com/nrk/predis library. So at the time the user authenticates, It publishes a message to Redis server.

Then you can set-up a little node server on the back-end - something simple like:

var server = require('http').Server();
var io = require('socket.io')(server);
var Redis = require('ioredis');
var redis = new Redis();

var authenticatedUsers = [];

// Subscribe to the authenticatedUsers channel in Redis
redis.subscribe('authenticatedUsers');

// Logic for what to do when a message is received from Redis
redis.on('message', function(channel, message) {
  authenticatedUsers.push(message);
  io.emit('userAuthenticated', message);
});

// What happens when a client connects
io.on('connection', function(socket) {
  console.log('connection', socket.id);

  socket.on('disconnect', function(a) {
    console.log('user disconnected', a);
  });
});

server.listen(3000);

Far from complete, but something to get you started.

Alternatively, take a look at Firebase. https://www.firebase.com/ if you dont want to bother with the server-side

score 3 · Answer 7 · answered Oct 06 '15 at 10:39

I would suggest using in built HTML5 session storage for this purpose. This is supported by all modern browsers so we will not face issues for the same.

This will help us to be efficient and quick to recognize if user is online. Whenever user moves mouse or presses keys update session storage with date and time. Check it periodically to see if it is empty or null and decide user left the site.

Arpita · Answer 8 · 2015-10-09T04:47:54.893

Instead of creating and deleting files you can do the same thing with cookie benefits of using cookie are

You do not need to hit ajax request to create a file on server as cookies are accessible by javascript/jquery.
Cookies have an option to set the time interval so would automatically delete themselves after a time, so you will not need php script to delete that.
Cookies are accessible by php, so when ever you need to check if user is still active or not, you can simply check if the cookie exist

score 3 · Answer 9 · answered Oct 08 '15 at 10:18

Depending on your resources you may opt for websockets or the previous method called long pool request. Both ensure a bidirectional communication between the server and the client. But they may be expensive on resources.

Here is an good tutorial on the websocket:

http://www.binarytides.com/websockets-php-tutorial/

Gillsoft AB · Answer 10 · 2015-10-08T20:41:43.703

I would use a callback that you (admin) can trigger. I use this technique in web app and mobile apps to (All this is set on the user side from the server):

Send a message to user (like: "behave or I ban you").
Update user status/location. (for events to know when attendants is arriving)
Terminate user connections (e.g. force log out if maintenance).
Set user report time (e.g. how often should the user report back)

The callback for the web app is usually in JavaScript, and you define when and how you want the user to call home. Think of it as a service channel.

score 2 · Answer 11 · answered Oct 08 '15 at 22:40

2

If it were aspnet I would say signalR... but for php perhaps you could look into Rachet it might help with a lot of what you are trying to accomplish as the messages could be pushed to the clients instead of client polling.

answered Oct 08 '15 at 22:40

Larry Dukek

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15
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colidyre · Answer 12 · 2016-01-31T11:31:55.533

Imo, there is no need for setting up solutions with bidirectional communications. You only want to know if a user is still logged in or attached to the system. If I understand you right, you only need a communication from server to client. So you can try SSE (server sent events) for that. The link gives you an idea, how to implement this with PHP.

The idea is simple. The server knows if user is attached or not. He could send something like "hey, user xyz is still logged in" or "hey, user xzy seems not to be logged in any more" and the client only listens to that messages and can react to the messages (e.g. via JavaScript).

The advantage is: SSE is really good for realtime applications, because the server only has to send data and the client has only to listen, see also the specification for this.

If you really need bidirectional communications or can't go with the two dependencies mentioned in the specs, it's not the best decision to use SSE, of course.

Here is a late Update with a nice chat example (written in Java). Probably it's also good to get an idea how to implement this in PHP.

How can I check in real time if a user is logged in?

12 Answers12