public class HomePageController {

public HomePageController()
{
  String unameParam = ApexPages.currentPage().getParameters().get('uname');
  if(unameparam == null)
  {
    // calling logout method to redirect to home page.
    Logout();
  }
}

public PageReference Logout() {
         System.debug('RCHOME ###');
         PageReference mainHome= Page.rc_home;
         mainHome.setRedirect(true);
         return mainHome;
}