While port 11501 is not a standardized default port (unlike 80 or 443), it is often used for:

The URL http://localhost:11501 designates a web service running on your local computer (localhost) using TCP port 11501. In the vast majority of use cases, this address is associated with software, specifically the UniFi Network Application when installed on a desktop operating system (Windows or macOS) or the UniFi Discovery Utility .