diff --git a/examples/python/client.py b/examples/python/client.py
index d6dd7aa6f49b253faed34d709bcf30b7f33f4272..312384d8cc72c1de30eddb0dc79d7f8641b329db 100644
--- a/examples/python/client.py
+++ b/examples/python/client.py
@@ -36,9 +36,11 @@ secDetectorsdklib.secUnsub.restype = None
 secDetectorsdklib.secReadFrom.argtypes = [ctypes.c_void_p, ctypes.c_char_p, ctypes.c_int]
 secDetectorsdklib.secReadFrom.restype = None
 
+g_read_flag = True
 
 def thread_func_sub_and_read(num=0):
     global g_cli_reader
+    global g_read_flag
 
     cli_reader = secDetectorsdklib.secSub(1)
     g_cli_reader_lock.acquire()
@@ -50,10 +52,7 @@ def thread_func_sub_and_read(num=0):
     secDetectorsdklib.secReadFrom(cli_reader, data, data_len)
     print("client read data:{}".format(data.value.decode()))
 
-    while True:
-        if data.value.decode() == 'end':
-            print("client received end")
-            break
+    while g_read_flag:
         time.sleep(3)
         secDetectorsdklib.secReadFrom(cli_reader, data, data_len)
         print("client while read data:{}".format(data.value.decode()))
@@ -62,8 +61,11 @@ def thread_func_sub_and_read(num=0):
 
 def thread_func_unsub(num=0):
     global g_cli_reader
+    global g_read_flag
+
     g_cli_reader_lock.acquire()
     try:
+        g_read_flag = False
         secDetectorsdklib.secUnsub(1, g_cli_reader)
     finally:
         g_cli_reader_lock.release()
diff --git a/lib/secDetector_sdk.cpp b/lib/secDetector_sdk.cpp
index ee760794508fb5dd8e12b63bf19ba3d008078b37..847dd2f85f6e0caf3252d847fe0bc9a17331f496 100644
--- a/lib/secDetector_sdk.cpp
+++ b/lib/secDetector_sdk.cpp
@@ -55,14 +55,14 @@ void secUnsub(const int topic, void *reader)
 	}
 
 	if (!reader)
-                return;
+		return;
 
-	g_client.Publish(topic, "end");
 	g_client.UnSubscribe(topic);
 	
 	Readmap::iterator iter = g_reader_map.find(reader);
 	if (iter != g_reader_map.end()) {
 		g_reader_map.erase(iter);
+		reader = NULL;
 	}
 }
 
@@ -70,13 +70,20 @@ void secReadFrom(void *reader, char *data, int data_len)
 {
 	string msg("");
 
-        if (!reader || !data || data_len <= 1)
-                return;
+	if (!data || data_len <= 1)
+		return
+
+	memset(data, 0, data_len);
+
+	if (!reader)
+		return;
 
 	Readmap::iterator iter = g_reader_map.find(reader);
-        if (iter != g_reader_map.end()) {
+	if (iter != g_reader_map.end()) {
 		msg = g_client.ReadFrom(iter->second);
-        }
+		if (msg == "keepalive")
+			return;
+	}
 
 	strncpy(data, msg.c_str(), data_len - 1);
 }
diff --git a/observer_agent/grpc_comm/server.cpp b/observer_agent/grpc_comm/server.cpp
index 54ae66fe1db95ebbfddd18b8a7b3f34f5bd59c0a..3340dfa054fa6c269a85cbeed94d6c1cf065e803 100644
--- a/observer_agent/grpc_comm/server.cpp
+++ b/observer_agent/grpc_comm/server.cpp
@@ -104,7 +104,6 @@ class PubSubServiceImpl final : public SubManager::Service
         keepalive_msg.set_text("keepalive");
         while (connect_status[tmp_index])
         {
-            sleep(CHECK_TIME);
             if (!writer->Write(keepalive_msg))
             {
                 for (auto topic_item : suber_topic_[cli_name])
@@ -124,6 +123,7 @@ class PubSubServiceImpl final : public SubManager::Service
                 }
                 return grpc::Status(grpc::StatusCode::INTERNAL, "writer is lose!");
             }
+            sleep(CHECK_TIME);
         }
         return grpc::Status::OK;
     }