Well your question is too broad. There are plenty of examples out there usin nodejs with socket.io. I suggest to study them first, understand nodejs and websockets, socket.io, rooms etc. Then show an effort to put something together, then ask for some help here. No offense but your question is basically a request from someone to do work for you, write the code and serve you in a golden plate.
I agree with Serdar Sanri,
Activity feed has nothing to do with socketio, you would manage it at database architecture and business logic in Nodejs. You can just send the activity feed data in real-time to the connected/subscribed client via socket.io
you can try Firecamp for the SocketIO and WS testing with GUI client here bit.ly/2rYbt7K
Serdar Sanri
Sr. Frontend Developer
Well your question is too broad. There are plenty of examples out there usin nodejs with socket.io. I suggest to study them first, understand nodejs and websockets, socket.io, rooms etc. Then show an effort to put something together, then ask for some help here. No offense but your question is basically a request from someone to do work for you, write the code and serve you in a golden plate.