Type Alias Outbox 

pub type Outbox = UnboundedSender<ServerMsg>;

A connection’s end of the fanout. Unbounded: a client that stops reading grows this queue rather than stalling the writer, which would stall every other client with it. Bounding it is a back-pressure decision to make when there is a real client to measure.

Aliased Type

pub struct Outbox { /* private fields */ }