윈도우 시간 동기화

/// <summary>
/// Gets the current DateTime from time-a.nist.gov.
/// </summary>
/// <returns>A DateTime containing the current time.</returns>
public static DateTime GetNetworkTime()
{
    return GetNetworkTime("time.windows.com"); // time-a.nist.gov
}
 
/// <summary>
/// Gets the current DateTime from <paramref name="ntpServer"/>.
/// </summary>
/// <param name="ntpServer">The hostname of the NTP server.</param>
/// <returns>A DateTime containing the current time.</returns>
public static DateTime GetNetworkTime(string ntpServer)
{
    IPAddress[] address = Dns.GetHostEntry(ntpServer).AddressList;
 
    if (address == null || address.Length == 0)
        throw new ArgumentException("Could not resolve ip address from '" + ntpServer + "'.", "ntpServer");
 
    IPEndPoint ep = new IPEndPoint(address[0], 123);
 
    return GetNetworkTime(ep);
}
 
/// <summary>
/// Gets the current DateTime form <paramref name="ep"/> IPEndPoint.
/// </summary>
/// <param name="ep">The IPEndPoint to connect to.</param>
/// <returns>A DateTime containing the current time.</returns>
public static DateTime GetNetworkTime(IPEndPoint ep)
{
    Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
 
    s.Connect(ep);
 
    byte[] ntpData = new byte[48]; // RFC 2030 
    ntpData[0] = 0x1B;
    for (int i = 1; i < 48; i++)
        ntpData[i] = 0;
 
    s.Send(ntpData);
    s.Receive(ntpData);
 
    byte offsetTransmitTime = 40;
    ulong intpart = 0;
    ulong fractpart = 0;
 
    for (int i = 0; i <= 3; i++)
        intpart = 256 * intpart + ntpData[offsetTransmitTime + i];
 
    for (int i = 4; i <= 7; i++)
        fractpart = 256 * fractpart + ntpData[offsetTransmitTime + i];
 
    ulong milliseconds = (intpart * 1000 + (fractpart * 1000) / 0x100000000L);
    s.Close();
 
    TimeSpan timeSpan = TimeSpan.FromTicks((long)milliseconds * TimeSpan.TicksPerMillisecond);
 
    DateTime dateTime = new DateTime(1900, 1, 1);
    dateTime += timeSpan;
 
    TimeSpan offsetAmount = TimeZone.CurrentTimeZone.GetUtcOffset(dateTime);
    DateTime networkDateTime = (dateTime + offsetAmount);
 
    return networkDateTime.AddHours(-9);
}


[DllImport("kernel32")]
public static extern int SetSystemTime(ref SYSTEMTIME lpSystemTime);
 
 
public struct SYSTEMTIME
{
    public short wYear; //년도
    public short wMonth; //월
    public short wDayOfWeek; //요일
    public short wDay; //일
    public short wHour; //시
    public short wMinute; //분
    public short wSecond; //초
    public short wMilliseconds; //1/100초
}
 
private void setNowTime()
{
    SYSTEMTIME sTime = new SYSTEMTIME();
    sTime.wYear = Convert.ToInt16(GetNetworkTime().Year);
    sTime.wMonth = Convert.ToInt16(GetNetworkTime().Month);
    sTime.wDayOfWeek = Convert.ToInt16(GetNetworkTime().DayOfWeek);
    sTime.wDay = Convert.ToInt16(GetNetworkTime().Day);
    sTime.wHour = Convert.ToInt16(GetNetworkTime().Hour);
    sTime.wMinute = Convert.ToInt16(GetNetworkTime().Minute);
    sTime.wSecond = Convert.ToInt16(GetNetworkTime().Second);
    sTime.wMilliseconds = Convert.ToInt16(GetNetworkTime().Millisecond);
    SetSystemTime(ref sTime);
}