The license slaves are connected to the license master via management port. License master every minute will hit the license slaves rest point at 8089 port which discloses information about license slave. If you see today's usage to open in search you will be able to find the rest command and what information is collected from slave. Also, you can try hitting the rest API directly to know what information is disclosed from slave to master.
Just nitpicking, but I don't think the License Master 'hits' the Slaves, at least from a TCP perspective.
Slaves open a socket to the webservice on the Master and send metrics to it. Its a minor point, but relevant if someone is having to configure firewall ports etc.
But in today's license usage when i opened in search it is using rest command hitting the rest point of the slaves. So i opened same rest API via 8089 port and found the same information. Based on the SPL i just understood this way.
The only thing the license server is concerned with is the amount of data being indexed. It monitors the amount of data that is indexed by other instances that are configured to use it as a license server. The instance type is unimportant.
