Reactivate AFP von Mac High Sierra OS X Server (10.13)
The item "File Sharing" is entirely removed from Server 5.4. You can still configure the settings in System Preferences > Sharing > File Sharing though.

If you you want to manage file sharing from the command line use:

sudo serveradmin ...


to enable or stop AFP and

sudo sharing ...


to manage shares.

Example: 

Enter sudo sharing -a /Volumes/Share/Users -A Users to share the folder /Volumes/Share/Users via AFP and the share name Users.

Check man sharing for further options and flags.



Shares on APFS volumes can't be shared via AFP!