How to write a Server Software?

For an upcoming project I need to write a server software to which the client can conntect over an Android App.

I know a simple Server could be written with Java or other programming languages. A very simple Server wouldn't be any problem for me.

But what if I want to do it in a professional way? There are a few things which whould be considered:

• How to keep the Server scalable?


• How to keep the Server secure?


• How to keep the Server stable?


• How to prevent others to access the Server? (via PC instead of the App)

I'm pretty sure there are much more questions..

I would like to collect some recommandetions for books or other sources where you can find such Information.