Where does the library receive updates?

[ARRAMAGA]

The documentation says:

Update events are sent to an authorized user into the last active connection (except for connections needed for downloading / uploading files).

So to start receiving updates the client needs to init connection and call API method, e.g. to fetch current state.

I've already looked at all the source code, but the most I found is processMessage in MtProtoSender, but it only handles manually sent requests

Another library based on TDLib handles incoming updates. Trying to understand how it does it, I got to this point. What is going on here and how can I do the same in TLSharp I do not understand

How to handle incoming updates sent by telegram?
P.S. updates.getDifference is not what i'm looking for