Frame msg and write it to a single listener (identified by listenerId),
rather than broadcasting to all. Used to deliver a per-stream leading event
— e.g. the notifications/subscriptions/acknowledged the draft
subscriptions/listen stream sends only to its own client. Returns true if
the listener received it; false if the id is unknown or its write failed
(in which case the listener is dropped).
Frame msg and write it to a single listener (identified by listenerId), rather than broadcasting to all. Used to deliver a per-stream leading event — e.g. the notifications/subscriptions/acknowledged the draft subscriptions/listen stream sends only to its own client. Returns true if the listener received it; false if the id is unknown or its write failed (in which case the listener is dropped).