How can share my scaner on over network ?

Keyspan Products by Tripp Lite (http://www.keyspan.com) makes devices that can do that. Look under serial servers.

You can set a scanner to share the same way you can with a printer. The option is in Control Panel > Scanners And Cameras. However you will need to be running SP2 in order for it to work due to firewall issues in < SP1