BuddyPress.org

@ mercime : thanks . But in that case, I have to re-design my login page, but I am not good at designing.

But I have created a new plugin for my-self which will display homepage to all users but only logged in users will be able to see other contents of the website.
soon I will upload the plugin and will let you know the URL to the plugin.Currently I am testing it with my site and it is working fine with default theme of Buddypress. If someone wants to test it, it is implemented on mycampus.cz.cc.