VNC's web-viewer port for display :2 — the second per-user desktop on a shared host.
5802 is 5800 plus display 2, the HTTP listener a VNC server opens alongside RFB on 5902. It shows up on multi-user Linux boxes where several people each run their own vncserver session, so displays climb :1, :2, :3 and the HTTP and RFB ports climb with them. The port is unassigned at IANA and exists purely by VNC convention.
Do not expose
A second exposed desktop is not safer than the first. Bind VNC to localhost and reach it over SSH.
$ curl -sS -o /dev/null -w '%{http_code}\n' http://TARGET:5802/Seen 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.
Get Beige Box →also available as JSON · Markdown
Corrections or a missing port? Reply @rimrocksystems.