Try RESTHeart Online
RESTHeart Webchat
This example application is developed with Angular. The backend is based on RESTHeart’s Change Streams to provide an instant, zero lines of code API for a realtime chat application. In turn, RESTHeart leverages MongoDB’s Change Streams to instantly notify clients about database modifications through WebSockets.
The source code is available at restheart-webchat
official Github repository!
How does it work?

Send a message with curl
Chat messages are sent via POST requests to https://demo.restheart.org/messages
Therefore you can also send a message with curl
with the following request or execute it on restninja
$ curl -i -H "Content-Type:application/json" -X POST https://demo.restheart.org/messages/ -d '{"from":"you", "message":"RESTHeart rocks!!" }'
HTTP/1.1 201 Created
To see another example visit A simple Angular demo!