Android : How to redirect users to only one site when i turn on hotspot in my android device?

Assume i have tablet with hotspot, for now i turn on the hotspot and when somebody connect to my access point he can surf wherever he wants. I want to restrict only to one site (my local site with unique ip and port). How can i do it? There is app from the market that can help?

I think i need to change the dns server or something but i dont know how exactly to do it.

The process: user click http://www.google.com he redirects to 192.168.20.12:8080, the user click http://www.stackoverflow.com he redirects to 192.168.20.12:8080 ,etc..