Commvault's core communications service — the backup platform's control channel.
IANA registers the bare name cvd on 8400 with no description, and the software behind it is Commvault: its firewall documentation lists "TCP 8400 — CVD services" as required between the CommServe, MediaAgents and clients, with 8401 (Server Event Manager) and 8402/8403/8405 alongside it. Every Commvault-managed machine runs the CVD service, so on an enterprise network 8400 usually marks a backup client or media agent. Outside that product the port is rare — Nmap sees it open on about 0.04% of hosts.
Do not expose
This is the control channel of a backup platform that holds copies of everything. Keep it inside the backup network or behind Commvault's own network-gateway/tunnel configuration, never on a public interface.
$ sudo lsof -nP -iTCP:8400 -sTCP:LISTENSeen 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.