I realize that I have given little information. I'm sorry.
Here is the information that were missing:
The game will run on HTML5, browser entirely saved on a server of my property.
The player will not have to download anything on your computer.
All data and developments of the player are saved on the server.
After a first recording fictitious (name, character class), the player will be able to access the game every time, without entering a password of sorts.
I want to make sure that the server remembers Player, locating it in some way, perhaps with the MAC address