As you say that you cannot share your local hard disk with the server,
the only sharing mechanism that is left is the clipboard.
If the clipboard is shareable over the RDP connection, you may use the open-source
project Clipboard RDC.
This project consists of a very small Java program that is launched on both
sides of the connection. The client-side program is used to encode a file
and load it to the clipboard, while the server-side program decodes and
stores it in a local file.
The limitation here is that the file must be small enough to fit on the clipboard.
As it stands, this is more work than you wanted to do.
But you can modify this simple program and separate it into two parts :
- A client-side program that will accept a file-path as parameter
and place the encoded file on the clipboard.
- A server-side program that will loop, testing every few seconds for the
presence of such a file on the clipboard, decoding and storing it in the folder.
As these will be your own programs that you fully control,
you could add features such
as adding the destination path to the information that you place on the
clipboard, so that this becomes a general-purpose tool for automatically transferring
multiple small-enough files from client to server.