[C++知识库]c语言实现sntp c语言实现秒数转换UTC

#include<stdio.h>
#include "unistd.h"
#include "sys/socket.h"
#include "netinet/in.h"
#include "arpa/inet.h"
#include "string.h"
#include "stdlib.h"
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>


#define IP "85.199.214.100"    // "0.uk.pool.ntp.org"
#define PORT 123

//此函数是实现秒数转换成UTC时间
Calc_Time(unsigned long Second_data)
{
    const int Days[12]={31,28,31,30,31,30,31,31,30,31,30,31};
    unsigned long Year = 1970;
    unsigned long Month = 1;
    unsigned long Day = 1;
    unsigned long Hour = 0;
    unsigned long Min = 0;
    unsigned long Second = 0;
 
    unsigned int Pass4year;
    int hours_per_year;
    if(Second_data < 0){
        Second_data = 0;
    }
    Second = Second_data%60;   //取秒
    Second_data /= 60;
    Min = Second_data%60;     //取分
    Second_data /= 60;   //余下的小时
 
     //过去有多少个4年，每4年有 1461*24小时
     Pass4year = Second_data/(1461*24);
     //计算年份
     Year = 1970 +Pass4year*4;
     //剩下的小时数
     Second_data = Second_data %(1461*24);
     //校正闰年影响的年份，计算一年中剩下的小时数
     for(;;)
     {
         //一年的hour = 365*24
         hours_per_year = 365*24;
         //判断闰年
         if((((Year%4)==0)&&((Year%100)!=0))  ||((Year%400)==0)){
 
             hours_per_year +=24;
         }
         if(Second_data < hours_per_year){
             break;
         }
         Year++;
         Second_data -= hours_per_year;
     }
     //小时数
     Hour = Second_data%24;
 
     Second_data /= 24;  //剩下的天数
 
     Second_data+=1;   //天数从1号开始
 
     if((((Year%4)==0)&&((Year%100)!=0)) ||((Year%400)==0)) {
         if(Second_data >60){
             Second_data--;
         }else {
             if(Second_data == 60) {
                 Day = 29;
                 Month = 1;
                 return;
             }
         }
     }
    
    //计算月日
     for(Month = 0;Days[Month]<Second_data;Month++){
         Second_data -= Days[Month];
     }
     Day = Second_data;
   Month = Month+1;
   printf("Year [%ld] :Month [%ld]: Day [%ld] :Hour  [%ld]: Min  [%ld]: Second  [%ld]",Year,Month,Day,Hour,Min,Second);
   return ;
}


int main()
{
    
    int fb=0,len=0;
    char buf[48]={'\0'};
    buf[0] = 3 | (4<<3);
    struct sockaddr_in List_buf,from;
    len=sizeof(List_buf);
    
    //创建套接字
    fb = socket(AF_INET,SOCK_DGRAM,0);
    List_buf.sin_family=AF_INET;
    List_buf.sin_port=htons(PORT);
    List_buf.sin_addr.s_addr=inet_addr(IP);
    bind(fb,(struct sockaddr *)&List_buf,len);

    //发送数据
    int ret = sendto(fb,buf,sizeof(buf),0,(struct sockaddr *)&List_buf,len);
    bzero(buf,48);
        //接收数据
    int rec = recvfrom(fb,buf,48,0,(struct sockaddr *)&List_buf,&len);
    printf("收到发来的信息rec[%d]>>\n",rec);
    printf("收到发来的信息buf%s>>\n",buf);

    int t  = 0;
    for(int i = 40; i <= 43; i++){
		unsigned char c = (unsigned char)buf[i];
		t = (t<<8) | c;
	}
	t -= 2208988800;	// 1970.1.1 0:0:0
	t += 8 * 60 * 60;	// UTC to Beijin
    Calc_Time(t);
	printf("收到发来的信息t[%d]>>\n",t);
    close(fb);
    return 0;
}