You can restrict the access to a 4D Server based on the IP address of the machine 4D Client runs on. This can be done by specifying a range of addresses that can connect to a specific 4D Server application. To do so, follow the steps below:

1-Locate the tcp.opt file
With version 6.5, that file should be located in the ACI preferences folder, with version 6.7 it should be located in the 4D preferences folder.

2- Copy that file next to the 4D Server application.
3- Open that copy using 4D Customizer Plus.
4- Specify an address range.
5- Save the changes and close the file.

The next time the 4D Server application is launched, these changes will take effect and a 4D Client whose IP address does not belong to the specified range will not be able to connect.