WhosOn is a client/server system for logon accounting. Use either whoson-php or whoson-asp on server side, with whoson-sql for SQL support. Install the Linux, Mac OS X or Windows client on computers from who logon session statistics should be collected.
Easiest is to record events by running the client as a logon/logoff script from i.e. an active directory GPO. The client can also be run as a service/daemon on client computers, monitoring user logons in the background.
Recorded data has IP, hostname, MAC, username, domain and datetime as field that is stored in the database. The client communicates with server side using SOAP.
By default, authentication is disabled on server side, but its possible to enable HTTP basic authentication against i.e. LDAP or plain text file.
The whoson application and library provides an SOAP client (Windows C#/.NET) for the WhosOn logon accounting service. The whoson-asp or whoson-php package should have been installed on the server side.