历史数据添加日期查询插件

src/app/services/websocket.service.ts

@@ -17,6 +17,10 @@ export class WebsocketService {
         }
 
         this.websocket = new WebSocket(url);
+        setInterval(() => {
+            let msg = { "topic": "heart-beat", "message": "" };
+            this.websocket.send(JSON.stringify(msg));
+        }, 30000);
         return new Observable(ob => {
             this.websocket.onopen = () => {
                 console.log('websocket was connected...')