Is it (somewhat easily) possible to have different callbacks registered on different ports (e.g.because the implement different protocols) without threads?
And for this, one needs to (also) hook some buffer transfer logic as the daemon mustn't block.

So the basic idea is:

• register various callbacks to various (different) ports
• the callbacks are called if data is available. the callback functions buffer the data and handle it, if enough data is here (e.a. a complete request).
• the response is constructed (non-blocking) and stored in some buffer (and is gradually transmitted).

Using threads just adds the complexity for internal explicit synchronization ....