Ask HN: Open Source (self hosted?) WhatsApp alternatives?

I am not going to rant and whine on how and why Facebook buying WhatsApp means private and intimate days of WhatsApp are over.

I just want to make sure that my photos in undies or my friends', or those careless conversations, or those stupid fantasies don't end up inside an advertiser's data-centre.

PS. Good if there's a Desktop app too. (Beta/alpha will do just fine).