diff --git a/gdata-characteristic.js b/gdata-characteristic.js
index 1a80861..ce4c359 100644
--- a/gdata-characteristic.js
+++ b/gdata-characteristic.js
@@ -11,18 +11,21 @@ device.open(()=>{
 
 var tmp = []
 
+const notifyDesciptor = new bleno.Descriptor({
+  uuid: '8888',
+  value: 0
+})
+
 class DataCharacteristic extends bleno.Characteristic {
   constructor() {
     super({
       uuid: config.uuid.service.func.data,
-      properties: ['write', 'writeWithoutResponse'],
+      properties: ['write', 'writeWithoutResponse', 'notify'],
       descriptors: [
-        new bleno.Descriptor({
-          uuid: '8888',
-          value: 'Now'
-        })
+        notifyDesciptor
       ]
     })
+    this._notifyFunc = null
   }
 
   onWriteRequest(data, offset, withoutResponse, callback) {
@@ -36,6 +39,9 @@ class DataCharacteristic extends bleno.Characteristic {
       //console.log(tmp)
       console.log(Buffer.from(tmp).toString())
       printString(Buffer.from(tmp).toString())
+      if(this._notifyFunc) {
+        this._notifyFunc(Buffer.from([0x00,0x01]))
+      }
     } else {
       tmp = [...tmp, ...data.slice(2, data.length)]
     }
@@ -44,6 +50,15 @@ class DataCharacteristic extends bleno.Characteristic {
       callback(this.RESULT_SUCCESS)
     }
   }
+
+  onSubscribe(maxValueSize, cb) {
+    console.log(maxValueSize)
+    this._notifyFunc = cb
+  }
+
+  onUnsubscribe () {
+    this._notifyFunc = null
+  }
 }