Built with socket.io and Express in the NodeJS environment.
View live site at https://socket-chat-app-v1.herokuapp.com
Different user can open this app and talk to each other.
If you want to simulate the multiplayer scenario on your own, you could simply open multiple tabs with this app from your browser, and talk to other 'tabs' (other users actually).
This is the first version, other advanced features and using database will be implemented in the next version.
Have fun!