internal/discovery registers three service types on the listen port:
_vellum._tcp for native clients, and _jellyfin._tcp / _subsonic._tcp
because those ecosystems already have clients that browse the LAN. That
last part is the point: Infuse, Jellyfin Media Player and Symfonium can
find Vellum with no client-side work, because they are already looking for
those names.
TXT records carry api, ver, proto, types, tls and (when set) pub, so a
client that resolves one can tell what it found before connecting.
Definitions is a pure function of config and Start only registers what it
returns, so what is advertised is testable without a socket.
Two behaviours worth knowing:
- VELLUM_DISCOVERY=off stops advertising. It accepts off/no/false/0;
strconv.ParseBool would have silently ignored "off".
- A loopback-only listen address advertises nothing. That is the normal
shape behind a reverse proxy, and advertising it would put a port in the
LAN browse list that refuses every client that dials it. Verified
red-green: defeating the guard fails TestDefinitionsSkipsLoopbackListen.
zeroconf is the only new dependency. It logs to the stdlib logger, so a
host with no multicast-capable interface prints to stderr outside slog.
Not verified: real mDNS on a real LAN. There is no multicast here, so the
wire behaviour of zeroconf is untested - only the definitions it is handed.
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