Are the files open on the other computer?
Open remote connects you to files that are already open on the host computer. They can be opened and thus "hosted" with either FileMaker Pro or FileMaker Server on the host computer.
Then the file's sharing options need to be correctly set.
Open the file with FileMaker Pro. Select Sharing | FileMaker Network from the File menu.
Select the file in the list of open files by clicking it and then click the "all users" radio button.
version 12 has a new file-format - therefore FM12 can't read .fp7 files. Since You can open the files using FM9, the hosted files seem to be .fp7...