事件：'prefinish'

🌐 Event: 'prefinish'

在调用 outgoingMessage.end() 后触发。 当事件被触发时，所有数据都已被处理，但不一定已完全刷新。

🌐 Emitted after outgoingMessage.end() is called. When the event is emitted, all data has been processed but not necessarily completely flushed.