You can put websocketd behind xinetd. xinetd doesn't talk websocket, so you still need to "provide a network mechanism" to bridge the incoming connection and the client's streams.
Because the point of xinetd is to spawn other daemons on socket activations. xinetd handling stuff itself is the exception not the rule (5 service are internally provided, none of which you want to run: RFC 862 "echo", RFC 863 "Discard", RFC 864 "CHARGEN", RFC 867 "daytime" and RFC 868 "time").
for example... simply accept stdin and stdout as I/O streams by default, but don't provide a network mechanism.