There are several ways to handle this situation. The most common way is to use a license file alias. This synchronized backup License File will stick around after your application is uninstalled, preventing the user from re-installing and starting over with another trial period. Another option is to require users to activate the trial. A comparison of these approaches can be found in this blog post.
For Protection PLUS 5 SDK, you can refer to the manual topics on validating time-limited licenses/trials for either PLUSManaged or PLUSNative.
With Protection PLUS 4 SDK, some ways to prevent trial re-installation include:
- Have the application only run for a limited time and have the user contact you for an evaluation trigger code which gives them a 30 day evaluation.
- Add a function to the application that destroys all required data files during installation. Each time the application is installed, the potential client would lose all data entered during the prior demo period.
- Ship with a license file with a date set to 0/0/0. When executing the application and the expiration date is set to 0/0/0, reset the expiration date to 30 days from today’s date and write that same date into a key data file with which the user would not disturb. When opening the data file, verify that date in data file matches expiration date. If not, don't open the data file. This will prohibit anyone from reinstalling the program and copying over the old data file. They will have to start with empty data files every time!
- Save the value of a few records in a database field into the license file upon exiting. When starting the application over, verify that the fields match. The Protection PLUS system function pp_password() converts a string over to a number for easy storage into one of the user-defined numeric fields of the License File.