feat: implement real-time Pub/Sub alert broadcast system and update docs/GRPC.md

lib/grpcentity/client.go

@@ -91,6 +91,31 @@ func AskDownloadFile(ctx context.Context, m protoapi.IoTServiceClient, fileName
 	return buffer, nil
 }
 
+func AskSubscribeAlerts(ctx context.Context, m protoapi.IoTServiceClient, clientId string, topic string) {
+	stream, err := m.SubscribeAlerts(ctx, &protoapi.AlertSubscription{
+		ClientId: clientId,
+		Topic:    topic,
+	})
+	if err != nil {
+		fmt.Println("Failed to subscribe alerts:", err)
+		return
+	}
+
+	for {
+		alert, err := stream.Recv()
+		if err == io.EOF {
+			fmt.Println("Alert subscription stream closed by server.")
+			break
+		}
+		if err != nil {
+			break
+		}
+		fmt.Printf("\n🔔 [ALERT RECEIVED] ID: %s | Device: %s | Msg: %s | Time: %s\n\n",
+			alert.GetAlertId(), alert.GetDeviceId(), alert.GetMessage(),
+			time.Unix(alert.GetTimestamp(), 0).Format("15:04:05"))
+	}
+}
+
 func ClientRun(addr string) {
 	conn, err := grpc.NewClient(addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
 	if err != nil {
@@ -99,6 +124,14 @@ func ClientRun(addr string) {
 	}
 
 	client := protoapi.NewIoTServiceClient(conn)
+
+	// 백그라운드에서 실시간 경보 구독 기동
+	alertCtx, alertCancel := context.WithCancel(context.Background())
+	defer alertCancel()
+	go AskSubscribeAlerts(alertCtx, client, "client-app-01", "temperature_warnings")
+	// 구독 리시버 채널 등록을 위해 50ms 슬립
+	time.Sleep(50 * time.Millisecond)
+
 	r, err := AskingDateTime(context.Background(), client)
 	if err != nil {
 		fmt.Println(err)
@@ -171,4 +204,15 @@ func ClientRun(addr string) {
 		}
 	}
 	fmt.Printf("Data Integrity Checked (Upload vs Download matches?): %t\n", isMatch)
+
+	// 7단계: 임계값 초과 온습도 전송을 통한 Pub/Sub 실시간 알림 유발 시뮬레이션
+	fmt.Println("Sending abnormal high-temperature sensing data (45.8°C)...")
+	alertRes, err := AskUpdateSensingData(context.Background(), client, "sensor-room-01", 45.8, 60.1)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Println("Abnormal Sensing Update Success:", alertRes.Success)
+	// 알림 이벤트가 비동기로 화면에 출력될 시간을 확보하기 위해 100ms 대기
+	time.Sleep(100 * time.Millisecond)
 }