如何在Windows Azure上使用NTP验证本地VM时钟？

{\"network\":\"2013-07-16T18:18:25.9558581Z\",\"server\":\"2013-07-16T18:18:52.5415999Z\"}

    static uint SwapEndianness(ulong x)
    {
        return (uint)(((x & 0x000000ff) << 24) +
                       ((x & 0x0000ff00) << 8) +
                       ((x & 0x00ff0000) >> 8) +
                       ((x & 0xff000000) >> 24));
    }

    static DateTime Update(string server)
    {
        // NTP message size - 16 bytes of the digest (RFC 2030)
        var ntpData = new byte[48];

        //Setting the Leap Indicator, Version Number and Mode values
        ntpData[0] = 0x1B; //LI = 0 (no warning), VN = 3 (IPv4 only), Mode = 3 (Client Mode)

        var addresses = Dns.GetHostEntry(server).AddressList;

        //The UDP port number assigned to NTP is 123
        var ipEndPoint = new IPEndPoint(addresses[0], NTPPort);
        //NTP uses UDP
        var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

        socket.Connect(ipEndPoint);

        socket.Send(ntpData);
        DateTime l_now = DateTime.UtcNow;
        socket.Receive(ntpData);
        socket.Close();

        //Offset to get to the \"Transmit Timestamp\" field (time at which the reply 
        //departed the server for the client, in 64-bit timestamp format.\"
        const byte serverReplyTime = 40;

        //Get the seconds part
        ulong intPart = BitConverter.ToUInt32(ntpData, serverReplyTime);

        //Get the seconds fraction
        ulong fractPart = BitConverter.ToUInt32(ntpData, serverReplyTime + 4);

        //Convert From big-endian to little-endian
        intPart = SwapEndianness(intPart);
        fractPart = SwapEndianness(fractPart);

        var milliseconds = (intPart * 1000) + ((fractPart * 1000) / 0x100000000L);

        //**UTC** time
        var l_networkTime = (new DateTime(_epocBaseTicks, DateTimeKind.Utc)).AddMilliseconds((long)milliseconds);
        _networkTimeDelta = l_networkTime.Ticks - l_now.Ticks ;
        return l_networkTime;
    }