Where is the mender server github project?

I see this: https://github.com/mendersoftware/mender
It looks like the client open source, but where is the server code?
In addition, where is the client-server protocol defined in the documentation?

Here is the docker based server project.

And http api’s here

https://docs.mender.io/2.4/apis

Thank you.
You mentioned: https://docs.mender.io/2.4/apis
Is this the API the mender client is talking to the server? Where is for example the “delta upgrade” API/protocol mentioned?

The binary delta update is not an API. It’s an update module and is documented here: Robust delta update rootfs