General Questions

Hi,
I use m0n0wall for WiFi network with Captive Portal via radius user authentication.
I want to get information such as the amount of data downloaded (all user/per user)
and how many (count) user used this network (the total number of connected hosts since the start wifi network) for statistics.
If anyone can recommend a solution/software/script to get this stats?

Study up on RADIUS.  It is more than just authentication, and if properly configured it tracks all the things you were asking for.  I know because we needed it for WISPr compliance.