AWS single user

I have some problems getting the webserver to just let one user log on. I use a Realm that are declared with NAHttpSetRealmSecurity (0, “Realm 1” NA_HTTP_SECURITY_SINGLE_ACCESS, NA_HTTP_SECURITY_BASIC_AUTHENTICATION); but the webserver serves more than one user with the same Username and password. Have I thought completely wrong or doesn´t NA_HTTP_SECURITY_SINGLE_ACCESS mean just one user?