開發環境：野火的stm32f407，rt-thread studio版本是版本: 2.2.6，stm32f4的資源包為0.2.2。以RT-Thread中Lan8720和lwip協議棧的使用文章創建的工程為基礎。

新建ntptest.c測試文件，移植以上參考的ntp代碼，整理后如下：

#include
#include
#define SERVER_IP "114.67.237.130"
#define SERVER_PORT 123
#define TIMEOUT 10
//宏定義
#define NTP_TIMESTAMP_DELTA 2208988800ull //number of seconds between 1900 and 1970，1900-1970的時間差
#define SEC_TIME_ZONE + (86060) //Beijing,GMT+8， 時區差
typedef struct
{
uint8_t li_vn_mode; // Eight bits. li, vn, and mode.
// li. Two bits. Leap indicator.
// vn. Three bits. Version number of the protocol.
// mode. Three bits. Client will pick mode 3 for client.
uint8_t stratum; // Eight bits. Stratum level of the local clock.
uint8_t poll; // Eight bits. Maximum interval between successive messages.
uint8_t precision; // Eight bits. Precision of the local clock.
uint32_t rootDelay; // 32 bits. Total round trip delay time.
uint32_t rootDispersion; // 32 bits. Max error aloud from primary clock source.
uint32_t refId; // 32 bits. Reference clock identifier.
uint32_t refTm_s; // 32 bits. Reference time-stamp seconds.
uint32_t refTm_f; // 32 bits. Reference time-stamp fraction of a second.
uint32_t origTm_s; // 32 bits. Originate time-stamp seconds.
uint32_t origTm_f; // 32 bits. Originate time-stamp fraction of a second.
uint32_t rxTm_s; // 32 bits. Received time-stamp seconds.
uint32_t rxTm_f; // 32 bits. Received time-stamp fraction of a second.
uint32_t txTm_s; // 32 bits and the most important field the client cares about. Transmit time-stamp seconds.
uint32_t txTm_f; // 32 bits. Transmit time-stamp fraction of a second.
} ntp_packet; // Total: 48 bytes.
int sockfd=-1;
int maxfd1;
fd_set readfds;
struct timeval timeout;
struct sockaddr_in servaddr;
int len;
int i;
uint8_t buf[48];
long local_timestamp;//uint32_t local_timestamp;
ntp_packet packet ;
struct tm * Net_time;
uint8_t NTP_Data[48]; //48字節的報文
int bsp_ntp_init(void)
{
NTP_Data[0]=0xa3;
//00100011, 0xa3,100 版本4
//00011011, 0x1b,011 版本3
//00010011, 0x13,010 版本2
//00001011, 0x0b,001 版本1
//后面分別發送了4個不同版本，都可以收到數據。
for(i=1;i<48;i++)NTP_Data[i]=0;//剩余的47字節為0
// servaddr.sin_family = AF_INET;
// servaddr.sin_port = htons(SERVER_PORT);
// servaddr.sin_addr.s_addr = inet_host(SERVER_IP);
servaddr.sin_family = AF_INET;
inet_pton(AF_INET, SERVER_IP, &servaddr.sin_addr.s_addr);
servaddr.sin_port = htons(SERVER_PORT);
if(sockfd>0)
{
//close(sockfd);
closesocket(sockfd);
sockfd=-1;
}
if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
{
return -1;
}
if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(struct sockaddr)) != 0)
{
//close(sockfd);
closesocket(sockfd);
sockfd=-1;
return -1;
}
return 0;
}
int bsp_read_ntp(void)
{
if(sockfd<0)
{
if(bsp_ntp_init()<0)
{
rt_kprintf("sockfd is errn");
return -1;
}
}
send(sockfd, NTP_Data, sizeof(NTP_Data), 0);
rt_kprintf("send n");
FD_ZERO(&readfds);
FD_SET(sockfd, &readfds);
maxfd1 = sockfd + 1;
timeout.tv_sec = TIMEOUT;
timeout.tv_usec = 0;
if (select(maxfd1, &readfds, NULL, NULL, &timeout) > 0)
{
if (FD_ISSET(sockfd, &readfds))
{
if ((len = recv(sockfd, buf, sizeof(buf), 0)) < 0)
{
//close(sockfd);
closesocket(sockfd);
sockfd=-1;
return -1;
}
packet.txTm_s = buf[40]<<24 | buf[40+1]<<16|buf[40+2]<<8 |buf[40+3];//由于本文的時間精度要求不高，故自己用服務器返回的時間作為對時的時間，并未用公式：時間差offset=（（T2-T1）+（T3-T4））/2。而是用T3作為對時基準時間。
local_timestamp = packet.txTm_s - NTP_TIMESTAMP_DELTA;//減去1970和1900的差值
rt_kprintf( "unix_timestamp=%ldn",local_timestamp);
local_timestamp +=SEC_TIME_ZONE; //加上北京的時間差，GMT+8
Net_time = localtime(&local_timestamp); //秒數轉換位標準時間
rt_kprintf("%d-%d-%d %d:%d:%drn",(Net_time->tm_year)+1900, (Net_time->tm_mon)+1, Net_time->tm_mday, Net_time->tm_hour,Net_time->tm_min,Net_time->tm_sec); //打印出時間
}
}
return 0;
}

主函數調用，代碼如下：

extern int bsp_ntp_init(void);
extern int bsp_read_ntp(void);
int main(void)
{
int count = 1;
rt_thread_mdelay(5000);
bsp_ntp_init();
while (count++)
{
LOG_D("Hello RT-Thread!");
rt_thread_mdelay(1000);
bsp_read_ntp();
}
return RT_EOK;
}

編譯無報錯，下載測試，測試結果如下：

選擇其中一個時間戳，利用時間戳轉換工具比對，結果如下：

結果正常。