diff --git a/include/mqtt.h b/include/mqtt.h
old mode 100755
new mode 100644
index b1d6214..4b51f0c
--- a/include/mqtt.h
+++ b/include/mqtt.h
@@ -92,7 +92,7 @@ typedef struct  {
 mqtt_client *mqtt_start(mqtt_settings *mqtt_info);
 void mqtt_stop();
 void mqtt_task(void *pvParameters);
-void mqtt_subscribe(mqtt_client *client, char *topic, uint8_t qos);
-void mqtt_publish(mqtt_client* client, char *topic, char *data, int len, int qos, int retain);
+void mqtt_subscribe(mqtt_client *client, const char *topic, uint8_t qos);
+void mqtt_publish(mqtt_client* client, const char *topic, const char *data, int len, int qos, int retain);
 void mqtt_detroy();
 #endif
diff --git a/mqtt.c b/mqtt.c
old mode 100755
new mode 100644
index 3da056b..e415a82
--- a/mqtt.c
+++ b/mqtt.c
@@ -509,7 +509,7 @@ mqtt_client *mqtt_start(mqtt_settings *settings)
     return client;
 }
 
-void mqtt_subscribe(mqtt_client *client, char *topic, uint8_t qos)
+void mqtt_subscribe(mqtt_client *client, const char *topic, uint8_t qos)
 {
     client->mqtt_state.outbound_message = mqtt_msg_subscribe(&client->mqtt_state.mqtt_connection,
                                           topic, qos,
@@ -518,7 +518,7 @@ void mqtt_subscribe(mqtt_client *client, char *topic, uint8_t qos)
     mqtt_queue(client);
 }
 
-void mqtt_publish(mqtt_client* client, char *topic, char *data, int len, int qos, int retain)
+void mqtt_publish(mqtt_client* client, const char *topic, const char *data, int len, int qos, int retain)
 {
 
     client->mqtt_state.outbound_message = mqtt_msg_publish(&client->mqtt_state.mqtt_connection,