If you want to make status changes, chat updates, push notifications and other events visible on your web application socket.io is one of the most popular solutions. Unfortunately, we have to use a JavaScript solution and cannot stick to our beloved symfony framework based on the even more beloved programming language PHP (just kidding) 
But now it’s possible to setup a symfony project and add real-time push capabilites based on the MercureBundle and the Mercure protocol. I will give you an overview about the Mercure protocol and its history and provide use cases. In a real world project we will setup and use the MercureBundle to broadcast data to different clients. And the best thing - it’s completly compatible to the latest versions of the HTTP protocol and browsers.
Prerequisites: A machine with Docker installed!