Need a fix in socket.io

I have a fully built chat application but it enables user to chat 1 on 1 and i also built group chat but in that it had an issue for example ( if socket had three user connected 1,2,3 the real time messaging work for first user and last user connected ) It is a simple task might take 10-20mins for socket developer.

Everything is ready just want to do socket room coding

(Note : you have to work on anydesk as it is a big project i can explain in detail in google meet and also propose if you can start work immediately )