// sntpsync console version, by rojer, 2002

#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <Winsock2.h>

int main(int argc, char* argv[]) {

   WORD wVersionRequested = MAKEWORD(2, 2);
   WSADATA wsaData;
   int err;
   SOCKET s;
   char *ntps;
   struct sockaddr_in sa;
   int len;
   SYSTEMTIME new_time = {0, 0, 0, 0, 0, 0, 0, 0};
   DWORD sec1900;
   FILETIME ft;
   ULONGLONG nanosec1900;
   ULARGE_INTEGER ftlint;
   fd_set sset = { 1 };
   int timeout = 3;
   TIMEVAL timeout_tv = {timeout, 0};
   hostent *h;

   struct {
     DWORD bf;
     DWORD root_delay;
     DWORD root_dispersion;
     DWORD ref_id;
     DWORD ref_tstamp_hi;
     DWORD ref_tstamp_lo;
     DWORD orig_tstamp_hi;
     DWORD orig_tstamp_lo;
     DWORD rcv_tstamp_hi;
     DWORD rcv_tstamp_lo;
     DWORD trans_tstamp_hi;
     DWORD trans_tstamp_lo;
     } ntp_message;

   printf("\nsntpsync - simple ntp (sntp, rfc1769) time synchronizer.\n");
   if (argc < 2 || argc > 3) {
      printf("usage: sntpsync server [timeout]\ndefault timeout is 3 seconds.\n");
      };
   printf("(c) rojer, 2002\n\n");
   if (argc < 2 || argc > 3) return 1;

   ntps = argv[1];
   if (argc == 3) timeout = atoi(argv[2]);

   if (timeout > 0) timeout_tv.tv_sec = timeout;

   if (err = WSAStartup(wVersionRequested, &wsaData)) {
      printf("Winsock init error: %d\n", err);
      return 1;
      }

   if ((s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == INVALID_SOCKET) {       
      printf("Socket error: %d\n", WSAGetLastError());
      return 1;
      }

   sa.sin_family = AF_INET;
   sa.sin_port = htons(123);

   if ((sa.sin_addr.S_un.S_addr = inet_addr(ntps)) == INADDR_NONE) {
      if ((h = gethostbyname(ntps)) == NULL) {
         printf("gethostbyname: could not resolve %s: %d\n", ntps, WSAGetLastError());
         return 1;
         }
      sa.sin_addr.S_un.S_addr = *((DWORD *)h->h_addr);
      }

   /* rfc1769 recommends these values for simple queries */
   ntp_message.bf = htonl(0x0b000000);

   ntp_message.root_delay = 0;
   ntp_message.root_dispersion = 0;
   ntp_message.ref_id = 0;
   ntp_message.ref_tstamp_hi = 0;
   ntp_message.ref_tstamp_lo = 0;
   ntp_message.orig_tstamp_hi = 0;
   ntp_message.orig_tstamp_lo = 0;
   ntp_message.rcv_tstamp_hi = 0;
   ntp_message.rcv_tstamp_lo = 0;
   ntp_message.trans_tstamp_hi = 0;
   ntp_message.trans_tstamp_lo = 0;

   if (sendto(s, (const char *) &ntp_message, sizeof(ntp_message), 0, (struct sockaddr *) &sa, sizeof(sa)) == SOCKET_ERROR) {
      printf("Socket write error: %d\n", WSAGetLastError());
      return 1;
      };

   len = sizeof(sa);


   sset.fd_array[0] = s;
   err = select(0, &sset, NULL, NULL, &timeout_tv);
   if (err == 0) {
      printf("select: socket read timeout\n");
      return 1;      
      }
   if (err == SOCKET_ERROR) {
      printf("select: socket error: %d\n", WSAGetLastError());
      return 1;      
      }

   if (recvfrom(s, (char *) &ntp_message, sizeof(ntp_message), 0, (struct sockaddr *) &sa, &len) == SOCKET_ERROR) {
      printf("Socket read error: %d\n", WSAGetLastError());
      return 1;
      };

   sec1900 = ntohl(ntp_message.trans_tstamp_hi);
   
   if (((ntohl(ntp_message.bf) >> 30) == 3) || (sec1900 == 0)) {
      printf("%s: time not synchronized.\n", ntps);
      return 1;
      }
   
   new_time.wYear = 1900;
   new_time.wDay = 1;
   new_time.wMonth = 1;
   new_time.wHour = new_time.wMinute = new_time.wSecond = new_time.wMilliseconds = 0;

   SystemTimeToFileTime(&new_time, &ft);
   nanosec1900 = (ULONGLONG)sec1900 * (ULONGLONG)10000000;

   ftlint.LowPart = ft.dwLowDateTime;
   ftlint.HighPart = ft.dwHighDateTime;

   ftlint.QuadPart += nanosec1900;

   ft.dwLowDateTime = ftlint.LowPart;
   ft.dwHighDateTime = ftlint.HighPart;

   FileTimeToSystemTime(&ft, &new_time);

   printf("new time: %d/%d/%d %d:%d.%d UTC\n", new_time.wDay, new_time.wMonth, new_time.wYear, new_time.wHour, new_time.wMinute, new_time.wSecond);
   if (SetSystemTime(&new_time) == 0) {
      printf("setsystemtime: error %d\n", GetLastError());
      return 1;
      }
   printf("time adjusted successfully.\n");
   return 0;

}