如何从服务器向客户端发送消息 - websockets

Question

我正在成功处理客户端消息/请求

object EchoService {

  def route: Route = path("ws-echo") {
    get {
      handleWebSocketMessages(echoService)
    }
  }

  val echoService: Flow[Message, Message, _] = Flow[Message].map {
    case TextMessage.Strict(txt) => TextMessage("ECHO: " + txt)
    case _ => TextMessage("Message type unsupported")
  }
}

如何从服务器向客户端发送消息？