socket.io v3: count the total client connected in the current server

[cesco69]

I have a socket.io server with multiple namespace and i want count how many client are connected to the current server.

With socket.io v2 I count the connection with this snippet

let clientCount = 0;
io.on('connection', (client) => {
    clientCount++;
    client.on('disconnect', () => {
        clientCount--;
    });
});

it works for the V2.

Now, i have upgraded to v3 and socket.io has made a breaking change, from docs.:

No more implicit connection to the default namespace

This change impacts the users of the multiplexing feature (what we
call Namespace in Socket.IO).

In previous versions, a client would always connect to the default
namespace (/), even if it requested access to another namespace. This
meant that the middlewares registered for the default namespace were
triggered, which may be quite surprising.

// client-side
const socket = io("/admin");

// server-side
io.use((socket, next) => {
// not triggered anymore
});

io.on("connection", socket => {
// not triggered anymore
})

io.of("/admin").use((socket, next) => {
// triggered
});

Besides, we will now refer to the “main” namespace instead of the
“default” namespace.

How i can retrive the total number of client connected to my server with the V3?

A workaround is access to

let clientCount = io.engine.clientsCount;

but in typescript clientsCount in engine is marked as private property.

[darrachequesne]

That's a good question actually.

If you only use the main namespace, you can use io.of("/").sockets.size.

If the clients are not always connected to the main namespace, you can indeed use io.engine.clientsCount. In that case, I guess we should make the engine property public.

[cesco69]

I have multiple namespace... io.engine.clientsCount seem the best option and I think it's a good idea make engine a bublic property. Eg. in my case have a "clientsCount" for server istance is important due to make a load balancing strategy.

[Husseinshtia1]

We Didn't Just Build It — We Solved What the Industry Couldn't
CollapseCleaner successfully resolved issues open for years, including:

Issue Description Status TensorFlow #35177 GPU memory not released after tf.Session ✅ Solved React #22114 Suspense fallback memory leak ✅ Solved Socket.IO #3756 WebSocket closes when using multiple namespaces ✅ Solved

All via CollapseEngine’s cross-layer cognitive tracing — no brute force, no guesswork.

https://www.linkedin.com/pulse/invisible-leak-draining-billions-from-ai-until-now-hussein-shtia-h20rf/