Mattermost rocks; a self-hosted web-based chat.
Mattermost is a self-hosted, fully-developed #slack alternative.
Own your data, and don’t be locked in to a vendor.
It’s real-time, and seamless. Push ‘real-time’ via websockets for the tech-heads out there.
I use it daily and recommend it to all my customers. Be free.
It has in-browser, desktop, and mobile clients. I use them all. So great!