Remote Login Issue with iPhone

I'm building a free App, that needs to present some data only to logged users. I'll try to explain myself better. Assuming the user is already registered into the database, the first time he choose the private area, a view asks him the username and password.

My problem is: 开发者_如何学JAVAhow should I send them to the server and see if it accepts the data?

I like to use the ASIHTTPRequest library and its ASIFormDataRequest class for easily POSTing data to a webserver and acting on the response.