//ntp_rev.c

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


#define  int8      char
#define  uint8     unsigned char
#define  uint32    unsigned int
#define  ulong32   unsigned long
#define  long32    long
#define  int32     int
#define  long64    long long

#define  debug 

//3600s*24h*(365days*70years+17days)
#define  From00to70 0x83aa7e80U

#define  NTPSVR  "192.168.2.8"        //myserver


#define  NTPPORT  123
typedef struct NTPPACKET
{
  uint8     li_vn_mode;
  uint8     stratum;
  uint8     poll;
  uint8     precision;                                         //有符号整数表示本地时钟精确度
  ulong32   root_delay;                                   //到达服务器的一次往返的总延时，是15到16位有符号的定点小数
  ulong32   root_dispersion;                           // 到达服务器的一次标准误差，是15－16位的无符号的定点小数
  int8      ref_id[4];
  ulong32   reftimestamphigh;                      //本地时钟最后被设定或校正的时间T4
  ulong32   reftimestamplow;
  ulong32   oritimestamphigh;                //向服务器请求分离客户机的时间戳，采用64位时标格式T1
  ulong32   oritimestamplow;
  ulong32   recvtimestamphigh;             //向服务器请求到客户机的时间戳，采用64位时标格式T2
  ulong32   recvtimestamplow;
  ulong32   trantimestamphigh;           //向客户机答复分离服务器的时间戳，采用64位时标格式T3，用T3来校正本地时间 
  ulong32   trantimestamplow;
}NTPPacket;

NTPPacket  ntppack,newpack;

//定义为long64,解决32位数的符号位问题
long64   firsttimestamp,finaltimestamp;
long64   diftime,delaytime;

void NTP_Init()
{
  bzero(&ntppack,sizeof(ntppack));
  ntppack.li_vn_mode=0x1b;//0|(3<<2)|(3<<5);
  //获取初始时间戳T1
  firsttimestamp="From00to70"+time(NULL);//-8*3600;
  ntppack.oritimestamphigh=htonl(firsttimestamp);
}




int main()
{

//  ulong32 clienttime;
//  ulong32 diftime,firsttimestamp,finaltimestamp;
 // fd_set  inset1;
  int32  sockfd;
  struct timeval tv,tv1;
  struct timezone tz;
  struct sockaddr_in addr;

  addr.sin_family=AF_INET;   //IPV4协议
  addr.sin_port =htons(NTPPORT);   //NTP专用的123端口
  addr.sin_addr.s_addr=inet_addr(NTPSVR);//INADDR_ANY,NTPSVR;   //校时服务器
  bzero(&(addr.sin_zero),8);   //清零

    /*build a socket */
  if((sockfd=socket(AF_INET,SOCK_DGRAM,0))<0)
    {
      perror("create socket error!\n");
      exit(1);
    }

   /*bind a port*/

    
  //  int  bDontLinger = 0;
   //setsockopt( socket, SOL_SOCKET, SO_DONTLINGER, ( const char* )&bDontLinger, sizeof( int ) );
//   int bReuseaddr=1;
//   setsockopt(sockfd,SOL_SOCKET ,SO_REUSEADDR,(const char*)&bReuseaddr,sizeof(int));
/*
     if(bind(sockfd,(struct sockaddr *)&addr,sizeof(struct sockaddr))==-1)
       {
           perror("bind error");
           exit(1);
       }
*/

  while(1)
   {
 
         NTP_Init();
       //发送数据请求包
   //  sendto(sockfd,&ntppack,sizeof(ntppack),
     //                                            0,(struct sockaddr *)&addr,sizeof(struct sockaddr));
      
  // recvfrom(s,buffer,sizeof(buffer),0,&addr,&addr_len);
 //  sendto(s,buffer,len,0,&addr,addr_len); 
  int recvbyte=0;
       printf("sockfd %d \n",sockfd);
      recvbyte=recv(sockfd,&newpack,sizeof(newpack),0);   //接收数据在newpack中。

   
     printf("OK %d  \n",recvbyte);   
  // printf("OK\n");
  
     if(recvbyte<0)             {
      perror