IANA leaves 5915 unassigned; anything listening is almost certainly VNC display :15.
IANA marks the whole block 5915-5962 Unassigned, so no service owns this number. The convention that fills it is RFB: a VNC server on display :N listens on 5900+N, which makes 5915 display :15. Hosts that hand out one display per VM or per user — QEMU/KVM, Proxmox (which documented 5900-5999 as its VNC console range), or a box running several Xvnc instances — climb into this range quickly.
Do not expose
An unregistered port in the VNC block is a remote-desktop session by default assumption; classic VNC auth is weak and unencrypted, so keep it behind SSH or a VPN.
$ nmap -Pn -sV -p 5915 TARGETSeen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.