TensorBoard's default HTTP port, squatting inside IANA's X11 range.
IANA registers 6000-6063 to X11, making 6006 display :6, but in practice almost everything you find here is TensorBoard: running tensorboard --logdir ... serves its web UI on 6006 and tells you to open http://localhost:6006. It is a plain HTTP server with no authentication and no authorization, reading whatever event files live under the log directory. It shows up on GPU boxes, notebook servers, and ML training containers, often port-forwarded rather than bound publicly.
Do not expose
TensorBoard has no login of any kind — anyone who reaches the port reads your training runs, hyperparameters, and any embedded data. Bind it to localhost and reach it through an SSH tunnel.
$ curl -sI http://TARGET:6006/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.
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Corrections or a missing port? Reply @rimrocksystems.