Hi;
I want to add extra labtop to the internet which has only one socket.i am using that internet in a library.can anybody tell me is it good idea to use hub or port for it to use one more labtop on that intenet line.and how these devices work

You would want to purchase a router. Wired or wireless would be up to you.

I'm going to move your post to the networking forum for more specific answers

can you give more details please?

Internet connection type...