使用C＃查询NTP服务器不会响应

Question

在尝试使用以下源代码从NTP服务器接收日期时间时，我遇到的问题是从我的家里我可以查询服务器，但是当我在工作时，流程停在：s.Receive（ntpData） ;

class Program
{
    static void Main(string[] args)
    {
        DateTime dt = NtpClient.GetNetworkTime();
    }
}

public class NtpClient
{

    public static DateTime GetNetworkTime()
    {
        return GetNetworkTime("time-a.nist.gov");
    }

    public static DateTime GetNetworkTime(string ntpServer)
    {
        IPAddress[] address = Dns.GetHostEntry(ntpServer).AddressList;

        if (address == null || address.Length == 0)
        {
            throw new ArgumentException("Couldn not resolve Time Server " + ntpServer + "." , "ntpServer");
        }

        IPEndPoint ep = new IPEndPoint(address[0], 123);

        return GetNetworkTime(ep);
    }

    public static DateTime GetNetworkTime(EndPoint 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;
    }
}

对我来说这闻起来像防火墙/网络问题，有什么想法吗？