I want to try host prosody server over tor network, but can't find any guides for it.
https://joinjabber.org/tutorials/service/tor/ might help, but I never tried setting this up either.
XMPP (aka Jabber) is the community-owned standard for real-time federated messaging.
For a quick start click here
JoinJabber.org support chat
JoinJabber.org admin support chat
XMPP.net Provider List
Also see JoinJabber.org FAQ