ASP.Net Chat Application similar to facebook

I need a asp.net chat application module to be developed in ASP.Net and C# with SQL Server being the backend. The application interface should be similar to facebook chat. Only friends can chat with each other ( I will provide the database structure). Users should be able to chat online and send offline messages. All the messages need to be stored in the database. Notification of received messages should be shown. User should be able to view previous messages anytime. For more clarification, send me pm