You can configure which users and groups can access the services you provide. Sometimes this method of access control is referred to as a service access control list (SACL).
You can create groups for specific services or for all services. By default, all users can connect to all enabled services from all network address ranges.
In addition to the users and groups you create, you can use some special groups like “Local Accounts” or “Network Accounts,” if available.
Select your server in the Server app sidebar, then click Access.
Click the “Allow connections from” pop-up menu, then choose “only some users.”
In the users and groups sheet, enter a user or group name.
To add more users or groups, click Add 
, then enter another name.
When you’ve added all the desired users and groups, click OK.
Select your server in the Server app sidebar, then click Access.
Click Add below the Custom Access list, then select the desired service.
Some services have more configurable settings in this sheet than just the user access pop-up menu.
Click the “Allow connections from” pop-up menu, then choose “only some users.”
In the users and groups sheet, enter a user or group name.
To add more users or groups, click Add , then enter another name.
When you’ve added all the desired users and groups, click OK.