Internet-Security.com TCP port 1500 details

IBM Spectrum Protect (formerly Tivoli Storage Manager, TSM) uses TCP port 1500 as the default server port for client backup/restore and archive sessions.
In typical deployments, TSM clients (dsmc) connect to the Spectrum Protect server on 1500/TCP; administrators often leave this default open on backup servers.
The legacy VLSI Technology Inc. License Manager (service name vlsi-lm) also used TCP port 1500 for floating license checkout by VLSI/EDA tools.
Beyond these cases, there are no widely adopted mainstream protocols known to commonly use TCP 1500.

TCP 1500