Differentiating users connected to a shiny server

Hello,

I've got a ShinyApp where I need to write files on the server and I want to distinguish between users connected to the shiny server. When I have authentication I can use session$user, but I need to be able to write my scripts independent of authentication. Is there something in the session variable that will enable me to uniquely identify the different browsers connected to the shiny server? Perhaps a cookie or something?

Thanks
John