Hello @ Endy Yan (STAR_ICT)
Port 6516 is used for WAC web-based management interface by default.
When set up WAC, the wizard needs us to open relevant port to allow communication between WAC and other servers.
The error message "Failed to reserve port 6516" most occurs when another application is using port 6516, you might use netstat -ano | findstr :6516 to check if there any process currently using this port.