NTP service

Prerequisites

• You have obtained the device credentials.

• You have downloaded C LinkSDK Extended.

Background information

Alibaba Cloud IoT Platform provides the Network Time Protocol (NTP) service. For more information, see NTP service.

Usage flow

The following sequence diagram shows the NTP service flow. The demos/ntp_basic_demo.c application is used as an example.

Step 1: Device initialization

1. Create a device handle and establish a connection for the device.

   static void* demo_device_init(char *product_key, char *device_name, char *device_secret, char *host, uint16_t port)
   {
       int32_t res = STATE_SUCCESS;
       /* Create a device. */
       void *device = aiot_device_create(product_key, device_name);
   	....
       ....
           
       res = aiot_device_connect(device);
       
   	....
       ....
       return device;
   }

2. Configure the NTP module.

   • Set the time synchronization callback function.

         /* Set the time synchronization callback function. */
         aiot_device_ntp_set_callback(device, demo_ntp_callback, NULL);

     Parameter description

     Parameter	Description
     device	The device handle.
     demo_ntp_callback	A custom callback function.
     NULL	The context parameter of the callback function. The example uses NULL.

   • Set the time zone.

         /* This demo uses UTC+8, the time zone for China. Therefore, the sample code prints the time in UTC+8 during runtime. */
         aiot_device_ntp_set_zone(device, 8);

     Parameter description

     Parameter	Description
     device	The device handle.
     8	The time zone. Examples: For UTC+8, set the value to 8. For UTC-3, set the value to -3.

Step 2: Send a time synchronization request

1. Send a time synchronization request.

   /* Send a time synchronization request. */
   aiot_device_ntp_request(device);

2. Time synchronization callback function.

   /* The time synchronization callback function. */
   static void demo_ntp_callback(void *device, const aiot_ntp_time_t *recv_time, void *userdata)
   {
       printf("ntp recv time %d-%d-%d %d:%d:%d %d\r\n", 
           recv_time->year, recv_time->mon, recv_time->day, 
           recv_time->hour, recv_time->min, recv_time->sec, recv_time->msec);
   }

   Parameter description

   Parameter	Description
   device	The device handle.
   recv_time	The returned time, which you can use directly.
   userdata	The context of the callback. The example uses NULL.

Step 3: Device deinitialization

 /* Disconnect the device and release its resources. */
 demo_device_deinit(device);