I know there is are way to marry spark to local server.
What about completely divorcing spark from its server?
Also, in which direction I dig to write my own protocol? I’m asking because I already have protocol on top of TCP and the current on in spark won’t work for me.
You can use SYSTEM_MODE(MANUAL) documented here: http://docs.spark.io/firmware/#advanced-system-modes-manual-mode
Since it’s your own protocol…I don’t have clues on where to dig.
TCP and UDP plus COAP is implemented for the core though
Does it use COAP over DTLS with raw keys of full scale x509? I just realized that thing I made is almost COUP, but with modified CurveCP instead of DTLS.
So if I could just change DTLS layer with my own that would be cool.
Have you considered using Voodoospark? It’s a custom firmware that exposes the Spark API via TCP:
http://voodoospark.me/
I did. I’ll probably just write my own stack on top of UDP, or get over myself and embrace x509.
Basically, if someone can point me where in the firmware sources CoAP over DTLS is happening, it would be much appreciated.
It’s not too hard to find resources. Just have to familiarise. 
Easier said than done!
@andoriyu - It'd be interesting to see what you come up with!