c - multiple session handling asp.net -

i new web developing , did research still cant find looking for

i on project involves 2 thing cloud web service app , cloud virtual machine(server). (azure)

the virtual machine jobs app request .

users logins web page , request service server (which made).

but how manage multiple users simultaneously doing , how manage if user closes browser , logins continue left.

i use asp.net on cloud service , c on server