Suggest me some good practices to keep socket-io connected in Android oreo

I faced the exact same problem working on a chat application so I know your pain. Our conclusion was:

you don't keep a connection alive 24/7, if you need to deliver a message to an user that has no connection alive, send a push message via Firebase.

If you want to keep a connection alive in background, you will face many problems. The first one, targeting Oreo, is that if your app is in background (definition of "background" in this context is here) it won't be allowed to run except for small time windows.

You can definitely use JobScheduler to run periodic tasks, they won't be executed at exact intervals or times to reduce battery usage (which is good) but it won't help you in keeping a connection alive. At best, you can use JobScheduler to periodically pull messages from you server. In order to use JobScheduler you need to create a JobService class.

JobIntentService is a new class introduced in API 26 of support library. It is a replacement for IntentService, it will run as a JobService on android API 26+ and as a Service (similar to IntentService in the sense that it will execute code in a background thread) on older APIs. On Oreo its background execution will still be limited so it won't help you in keeping a connection alive.

Using a foreground Service can really help you reducing the likelihood of the process being killed, but, you will need to display a permanent notification. It doesn't sound like a good solution for a chat app.

If you still think that having a 24/7 connection alive is a viable option, you need to consider also doze mode. You could ask the user to whitelist your app to run even in doze mode but you should have a very good reason to do that. Again, you would face the other bg execution limit in Oreo.

Another issue you will face is other apps. There are resources management apps that will aggressively kill other apps in bg to reduce memory and battery usage. For instance, I cursed this one quite a bit.

Another issue is created by android. When the system is running low on memory, it will start killing processes of apps in bg. There is a an order in which they're killed, if I recall correctly should take into account last time it was in fg and current memory usage. Not the worst of the problems but still, it happens.

Then, if I still haven't convinced you in giving up the idea of the permanent connection, let me share with you yet another problem you would face. Some vendors implements extremely aggressive policies when it comes to killing bg processes, so that they're battery will last longer. For instance, Xiaomi.

Last tip, unrelated, but it took us a while to figure this out so I'm going to share it. If the user force stops your app from settings, your app is dead (that is, "stopped state") until the user actively launches it again, it won't even receive Firebase push messages.

If your server is configured on XMPP, then it would be easy for you. Actually, there isn't any need to keep the socket alive at all the time. This is very expensive for the battery and I'm sure you don't want that.

Case: You are working on a Messaging app.

If your socket is broken, then the client will receive the message in the form of Google FIREBASE notification. And the moment your client will receive a notification from firebase, just enable the socket, and you'll be back on track. The reason I suggested you to use XMPP is because XMPP maintains a queue of undelivered/offline messages. And when your socket is connected again, you simply pull the offline messages from the server.

I don't think this will help you out, but this may make a room for some another idea for you.