如何使用C＃查询NTP服务器？

  • Z时代
  • 2024-01-10
  • 分类：问答

我需要的是一种使用C＃查询NTP服务器的方法，以获取NTP服务器的日期时间，以a string或as形式返回DateTime。

最简单的形式怎么可能？

回答：

由于旧的答案被删除了（它是指向不再存在的Google代码搜索结果的链接），我认为我可以回答这个问题以供将来参考：

public static DateTime GetNetworkTime()
{
    //default Windows time server
    const string ntpServer = "time.windows.com";
    // 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(ntpServer).AddressList;
    //The UDP port number assigned to NTP is 123
    var ipEndPoint = new IPEndPoint(addresses[0], 123);
    //NTP uses UDP
    using(var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp))
    {
        socket.Connect(ipEndPoint);
        //Stops code hang if NTP is blocked
        socket.ReceiveTimeout = 3000;
        socket.Send(ntpData);
        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 networkDateTime = (new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc)).AddMilliseconds((long)milliseconds);
    return networkDateTime.ToLocalTime();
}
// stackoverflow.com/a/3294698/162671
static uint SwapEndianness(ulong x)
{
    return (uint) (((x & 0x000000ff) << 24) +
                   ((x & 0x0000ff00) << 8) +
                   ((x & 0x00ff0000) >> 8) +
                   ((x & 0xff000000) >> 24));
}

您将必须添加以下名称空间

using System.Net;
using System.Net.Sockets;

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