Adding a communication channel between server and clients using SSE

ui/src/reducers/activityReducer.js

@@ -0,0 +1,16 @@
+import { ACTIVITY_SCAN_STATUS_UPD } from '../actions'
+
+export const activityReducer = (
+  previousState = {
+    scanStatus: { scanning: false, count: 0 },
+  },
+  payload
+) => {
+  const { type, data } = payload
+  switch (type) {
+    case ACTIVITY_SCAN_STATUS_UPD:
+      return { ...previousState, scanStatus: data }
+    default:
+      return previousState
+  }
+}