How to advertise services to mDNS

[ghost07]

Hello, is there any mDNS protocol description?
I would like to only advertise some services, but I don't want to run mDNS server, keep track about other devices on network and so on.
So I don't want to use whole mdns library with all that unnecessary functionality.

I think about send some packet saying something like: "Hi all, I am [device_name], and I can provide [service_list]". For example in 1 minute interval or so.

Can I do that, even if no one in the network was asking?

And how should such packet look like? I mean, how do I advertise A, PTR, SRV, TXT records?

[ESP_Sprite]

As with most Internet-ish protocols, mDNS is documented in a RFC. Suggest you check that.