Question

Is it possible to compile application like Stunnel with libssl into iOS app, when app launch, it runs Stunnel with a conf parameters? Stunnel will open a TCP port.

Answer 1

You cannot do it exactly as you have stated it because iOS will not allow to fork a process.
But what you can do is rename the main procedure of Stunnel to something like stunnel_main, compile the sources of stunnel into your app (by adding the relevant source files to your project). When your app starts executing, create a new thread that calls stunnel_main with whatever parameters you want.

It’s not pretty, but it will work.