Based on your question I presume that your laptop is actually using a private IP.
Networking between these two machines in your 'home' network
(that is, without communicating over the Internet)
will need a private IP configured on your desktop (this is easily done with an alias)
How are the laptop, desktop and the Internet path connected?
Do you have two interfaces on the desktop (say one wireless and one wired)
such that one is used to connect to the Internet and the other to connect with your laptop?
If you can get this done, it would be as simple as setting up a private IP address
in the same subnet as your laptop on this second interface of your desktop.