How to check if subscribers are still online

So a client registers for a specific channel to the server.
On the server I can request GetAllSubscriptionInfos to get all subscribers. That’s working.
But, when I stop the client, this method keeps telling me active subscriber while it’s offline.
i thought I could use the _serverEvents.Pulse(subscriptionInfo.SubscriptionId) to see if the client was still active, but this also gives true.
What is the best way, server-side, to check whether a client (based upon channel) is still active?

You can use ServerEventsClient.GetChannelSubscribers (/event-subscribers) to find out the channels subscribers. Keep in mind it returns what subscriptions the server believes is still subscribed to the channel which may require the IdleTimeout to elapse before the Server removes the stale connection if the client didn’t make an explicit call to UnRegisterEventSubscriber (/event-unregister) to notify the server to unregister their connection.

Okay, but requesting this client-side method on the servers, adds a new subscriber to the channel, which I do not want.
So my best shot is to handle the OnHeartBeatInit and then trying to figure out who is sending the heartbeat and then keeping this is cached memory to know who is online?

It doesn’t, it’s just calling ServerEvents.GetSubscriptionsDetails to return all subscriptions currently subscribed to the channels specified.