程式碼如下：

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Threading ;
using System.IO;
using System.Net.Sockets;
using System.Text;
using System.Net;

namespace AutoExitWindows
{
 // Leap indicator field values
 public enum _LeapIndicator
 {
  NoWarning,  // 0 - No warning
  LastMinute61, // 1 - Last minute has 61 seconds
  LastMinute59, // 2 - Last minute has 59 seconds
  Alarm   // 3 - Alarm condition (clock not synchronized)
 }

 //Mode field values
 public enum _Mode
 {
  SymmetricActive, // 1 - Symmetric active
  SymmetricPassive, // 2 - Symmetric pasive
  Client,    // 3 - Client
  Server,    // 4 - Server
  Broadcast,   // 5 - Broadcast
  Unknown    // 0, 6, 7 - Reserved
 }

 // Stratum field values
 public enum _Stratum
 {
  Unspecified,   // 0 - unspecified or unavailable
  PrimaryReference,  // 1 - primary reference (e.g. radio-clock)
  SecondaryReference,  // 2-15 - secondary reference (via NTP or SNTP)
  Reserved    // 16-255 - reserved
 }

 /// <summary>
 /// SNTPTimeClient 的摘要說明。
 ///
 /// Public class members:
 ///
 /// LeapIndicator - Warns of an impending leap second to be inserted/deleted in the last
 /// minute of the current day. (See the _LeapIndicator enum)
 ///
 /// VersionNumber - Version number of the protocol (3 or 4).
 ///
 /// Mode - Returns mode. (See the _Mode enum)
 ///
 /// Stratum - Stratum of the clock. (See the _Stratum enum)
 ///
 /// PollInterval - Maximum interval between successive messages.
 ///
 /// Precision - Precision of the clock.
 ///
 /// RootDelay - Round trip time to the primary reference source.
 ///
 /// RootDispersion - Nominal error relative to the primary reference source.
 ///
 /// ReferenceID - Reference identifier (either a 4 character string or an IP address).
 ///
 /// ReferenceTimestamp - The time at which the clock was last set or corrected.
 ///
 /// OriginateTimestamp - The time at which the request departed the client for the server.
 ///
 /// ReceiveTimestamp - The time at which the request arrived at the server.
 ///
 /// Transmit Timestamp - The time at which the reply departed the server for client.
 ///
 /// RoundTripDelay - The time between the departure of request and arrival of reply.
 ///
 /// LocalClockOffset - The offset of the local clock relative to the primary reference
 /// source.
 ///
 /// Initialize - Sets up data structure and prepares for connection.
 ///
 /// Connect - Connects to the time server and populates the data structure.
 ///
 /// IsResponseValid - Returns true if received data is valid and if comes from
 /// a NTP-compliant time server.
 ///
 /// ToString - Returns a string representation of the object.
 ///
 /// -----------------------------------------------------------------------------
 /// Structure of the standard NTP header (as described in RFC 2030)
 ///                       1                   2                   3
 ///   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |LI | VN  |Mode |    Stratum    |     Poll      |   Precision   |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |                          Root Delay                           |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |                       Root Dispersion                         |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |                     Reference Identifier                      |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |                                                               |
 ///  |                   Reference Timestamp (64)                    |
 ///  |                                                               |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |                                                               |
 ///  |                   Originate Timestamp (64)                    |
 ///  |                                                               |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |                                                               |
 ///  |                    Receive Timestamp (64)                     |
 ///  |                                                               |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |                                                               |
 ///  |                    Transmit Timestamp (64)                    |
 ///  |                                                               |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |                 Key Identifier (optional) (32)                |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///  |                                                               |
 ///  |                                                               |
 ///  |                 Message Digest (optional) (128)               |
 ///  |                                                               |
 ///  |                                                               |
 ///  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///
 /// -----------------------------------------------------------------------------
 ///
 /// NTP Timestamp Format (as described in RFC 2030)
 ///                         1                   2                   3
 ///     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 /// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 /// |                           Seconds                             |
 /// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 /// |                  Seconds Fraction (0-padded)                  |
 /// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ///
 /// </summary>
 public class SNTPTimeClient
 {
  // NTP Data Structure Length
  private const byte NTPDataLength = 48;
  // NTP Data Structure (as described in RFC 2030)
  byte []NTPData = new byte[NTPDataLength];

  // Offset constants for timestamps in the data structure
  private const byte offReferenceID   = 12;
  private const byte offReferenceTimestamp = 16;
  private const byte offOriginateTimestamp = 24;
  private const byte offReceiveTimestamp   = 32;
  private const byte offTransmitTimestamp  = 40;

  // Leap Indicator
  public _LeapIndicator LeapIndicator
  {
   get
   {
    // Isolate the two most significant bits
    byte val = (byte)(NTPData[0] >> 6);
    switch(val)
    {
     case 0: return _LeapIndicator.NoWarning;
     case 1: return _LeapIndicator.LastMinute61;
     case 2: return _LeapIndicator.LastMinute59;
     case 3:
     default:
      return _LeapIndicator.Alarm;
    }
   }
  }

  // Version Number
  public byte VersionNumber
  {
   get
   {
    // Isolate bits 3 - 5
    byte val = (byte)((NTPData[0] & 0x38) >> 3);
    return val;
   }
  }

  // Mode
  public _Mode Mode
  {
   get
   {
    // Isolate bits 0 - 3
    byte val = (byte)(NTPData[0] & 0x7);
    switch(val)
    {
     case 0:
     case 6:
     case 7:
     default:
      return _Mode.Unknown;
     case 1:
      return _Mode.SymmetricActive;
     case 2:
      return _Mode.SymmetricPassive;
     case 3:
      return _Mode.Client;
     case 4:
      return _Mode.Server;
     case 5:
      return _Mode.Broadcast;
    }
   }
  }

  // Stratum
  public _Stratum Stratum
  {
   get
   {
    byte val = (byte)NTPData[1];
    if(val == 0) return _Stratum.Unspecified;
    else
     if(val == 1) return _Stratum.PrimaryReference;
    else
     if(val <= 15) return _Stratum.SecondaryReference;
    else
     return _Stratum.Reserved;
   }
  }

  // Poll Interval
  public uint PollInterval
  {
   get
   {
    return (uint)Math.Round(Math.Pow(2, NTPData[2]));
   }
  }

  // Precision (in milliseconds)
  public double Precision
  {
   get
   {
    return (1000 * Math.Pow(2, NTPData[3]));
   }
  }

  // Root Delay (in milliseconds)
  public double RootDelay
  {
   get
   {
    int temp = 0;
    temp = 256 * (256 * (256 * NTPData[4] + NTPData[5]) + NTPData[6]) + NTPData[7];
    return 1000 * (((double)temp) / 0x10000);
   }
  }

  // Root Dispersion (in milliseconds)
  public double RootDispersion
  {
   get
   {
    int temp = 0;
    temp = 256 * (256 * (256 * NTPData[8] + NTPData[9]) + NTPData[10]) + NTPData[11];
    return 1000 * (((double)temp) / 0x10000);
   }
  }

  // Reference Identifier
  public string ReferenceID
  {
   get
   {
    string val = "";
    switch(Stratum)
    {
     case _Stratum.Unspecified:
     case _Stratum.PrimaryReference:
      val += Convert.ToChar(NTPData[offReferenceID + 0]);
      val += Convert.ToChar(NTPData[offReferenceID + 1]);
      val += Convert.ToChar(NTPData[offReferenceID + 2]);
      val += Convert.ToChar(NTPData[offReferenceID + 3]);
      break;
     case _Stratum.SecondaryReference:
      ////     switch(VersionNumber)
      ////     {
      ////      case 3: // Version 3, Reference ID is an IPv4 address
      ////       string Address = NTPData[offReferenceID + 0].ToString() + "." +
      ////        NTPData[offReferenceID + 1].ToString() + "." +
      ////        NTPData[offReferenceID + 2].ToString() + "." +
      ////        NTPData[offReferenceID + 3].ToString();
      ////       try
      ////       {
      ////        IPAddress RefAddr = new IPAddress(Address);
      ////        IPHostEntry Host = DNS.GetHostByAddr(RefAddr);
      ////        val = Host.Hostname + " (" + Address + ")";
      ////       }
      ////       catch(Exception)
      ////       {
      ////        val = "N/A";
      ////       }
      ////     
      ////       break;
      ////      case 4: // Version 4, Reference ID is the timestamp of last update
      ////       DateTime time = ComputeDate(GetMilliSeconds(offReferenceID));
      ////       // Take care of the time zone
      ////       long offset = TimeZone.CurrentTimeZone.GetUTCOffset(DateTime.Now);
      ////       TimeSpan offspan = TimeSpan.FromTicks(offset);
      ////       val = (time + offspan).ToString();
      ////       break;
      ////      default:
      ////       val = "N/A";
      ////     }
      break;
    }

    return val;
   }
  }

  // Reference Timestamp
  public DateTime ReferenceTimestamp
  {
   get
   {
    DateTime time = ComputeDate(GetMilliSeconds(offReferenceTimestamp));
    // Take care of the time zone
    long offset = Convert.ToInt64 (TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now));
    TimeSpan offspan = TimeSpan.FromTicks(offset);
    return time + offspan;
   }
  }

  // Originate Timestamp
  public DateTime OriginateTimestamp
  {
   get
   {
    return ComputeDate(GetMilliSeconds(offOriginateTimestamp));
   }
  }

  // Receive Timestamp
  public DateTime ReceiveTimestamp
  {
   get
   {
    DateTime time = ComputeDate(GetMilliSeconds(offReceiveTimestamp));
    // Take care of the time zone
    long offset = TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now).Ticks;
    TimeSpan offspan = TimeSpan.FromTicks(offset);
    return time + offspan;
   }
  }

  // Transmit Timestamp
  public DateTime TransmitTimestamp
  {
   get
   {
    DateTime time = ComputeDate(GetMilliSeconds(offTransmitTimestamp));
    // Take care of the time zone    
    long offset =  TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now).Ticks;
    TimeSpan offspan = TimeSpan.FromTicks(offset);
    return time + offspan;
   }
   set
   {
    SetDate(offTransmitTimestamp, value);
   }
  }

  // Reception Timestamp
  public DateTime ReceptionTimestamp;
  
  // Round trip delay (in milliseconds)
  public int RoundTripDelay
  {
   get
   {
    TimeSpan span = (ReceiveTimestamp - OriginateTimestamp) + (ReceptionTimestamp - TransmitTimestamp);
    return (int)span.TotalMilliseconds;
   }
  }

  // Local clock offset (in milliseconds)
  public int LocalClockOffset
  {
   get
   {
    TimeSpan span = (ReceiveTimestamp - OriginateTimestamp) - (ReceptionTimestamp - TransmitTimestamp);
    return (int)(span.TotalMilliseconds / 2);
   }
  }

  // Compute date, given the number of milliseconds since January 1, 1900
  private DateTime ComputeDate(ulong milliseconds)
  {
   TimeSpan span = TimeSpan.FromMilliseconds((double)milliseconds);
   DateTime time = new DateTime(1900, 1, 1);
   time += span;
   return time;
  }

  // Compute the number of milliseconds, given the offset of a 8-byte array
  private ulong GetMilliSeconds(byte offset)
  {
   ulong intpart = 0, fractpart = 0;

   for(int i = 0; i <= 3; i++)
   {
    intpart = 256 * intpart + NTPData[offset + i]; 
   }
   for(int i = 4; i<=7; i++)
   {
    fractpart = 256 * fractpart + NTPData[offset + i];
   }
   ulong milliseconds = intpart * 1000 + (fractpart * 1000) / 0x100000000L;
   return milliseconds;
  }

  // Compute the 8-byte array, given the date
  private void SetDate(byte offset, DateTime date)
  {
   ulong intpart = 0, fractpart = 0;
   DateTime StartOfCentury = new DateTime(1900, 1, 1, 0, 0, 0); // January 1, 1900 12:00 AM

   ulong milliseconds = (ulong)(date - StartOfCentury).TotalMilliseconds;
   intpart = milliseconds / 1000;
   fractpart=((milliseconds % 1000) * 0x100000000L) / 1000;

   ulong temp = intpart;
   for(int i = 3; i >= 0; i--)
   {
    NTPData[offset + i] = (byte) (temp % 256);
    temp = temp / 256;
   }

   temp = fractpart;
   for(int i = 7; i >=4; i--)
   {
    NTPData[offset + i] = (byte) (temp % 256);
    temp = temp / 256;
   }
  }

  // Initialize the NTPClient data
  private void Initialize()
  {
   // Set version number to 4 and Mode to 3 (client)
   NTPData[0] = 0x1B;
   // Initialize all other fields with 0
   for(int i = 1; i < 48; i++)
   {
    NTPData[i] = 0;
   }
   // Initialize the transmit timestamp
   TransmitTimestamp = DateTime.Now;
  }

  // Connect to the time server
  public void Connect()
  {
   try
   {
    IPAddress hostadd = IPAddress.Parse(TimeServer);
    IPEndPoint EPhost = new IPEndPoint(hostadd, Convert.ToInt32(TimePort));

    UdpClient TimeSocket = new UdpClient();     
    TimeSocket.Connect(EPhost);
    Initialize();
    TimeSocket.Send(NTPData, NTPData.Length);
    NTPData = TimeSocket.Receive(ref EPhost);
    if(!IsResponseValid())
    {
     throw new Exception("Invalid response from " + TimeServer);
    }
    ReceptionTimestamp = DateTime.Now;
   }
   catch(SocketException e)
   {
    throw new Exception(e.Message);
   }
  }

  // Check if the response from server is valid
  public bool IsResponseValid()
  {
   if(NTPData.Length < NTPDataLength || Mode != _Mode.Server)
   {
    return false;
   }
   else
   {
    return true;
   }
  }

  // Converts the object to string
  public override string ToString()
  {
   string str;

   str = "Leap Indicator: ";
   switch(LeapIndicator)
   {
    case _LeapIndicator.NoWarning:
     str += "No warning";
     break;
    case _LeapIndicator.LastMinute61:
     str += "Last minute has 61 seconds";
     break;
    case _LeapIndicator.LastMinute59:
     str += "Last minute has 59 seconds";
     break;
    case _LeapIndicator.Alarm:
     str += "Alarm Condition (clock not synchronized)";
     break;
   }
   str += "/r/nVersion number: " + VersionNumber.ToString() + "/r/n";
   str += "Mode: ";
   switch(Mode)
   {
    case _Mode.Unknown:
     str += "Unknown";
     break;
    case _Mode.SymmetricActive:
     str += "Symmetric Active";
     break;
    case _Mode.SymmetricPassive:
     str += "Symmetric Pasive";
     break;
    case _Mode.Client:
     str += "Client";
     break;
    case _Mode.Server:
     str += "Server";
     break;
    case _Mode.Broadcast:
     str += "Broadcast";
     break;
   }
   str += "/r/nStratum: ";
   switch(Stratum)
   {
    case _Stratum.Unspecified:
    case _Stratum.Reserved:
     str += "Unspecified";
     break;
    case _Stratum.PrimaryReference:
     str += "Primary Reference";
     break;
    case _Stratum.SecondaryReference:
     str += "Secondary Reference";
     break;
   }
   str += "/r/nLocal time: " + TransmitTimestamp.ToString();
   str += "/r/nPrecision: " + Precision.ToString() + " ms";
   str += "/r/nPoll Interval: " + PollInterval.ToString() + " s";
   str += "/r/nReference ID: " + ReferenceID.ToString();
   str += "/r/nRoot Dispersion: " + RootDispersion.ToString() + " ms";
   str += "/r/nRound Trip Delay: " + RoundTripDelay.ToString() + " ms";
   str += "/r/nLocal Clock Offset: " + LocalClockOffset.ToString() + " ms";
   str += "/r/n";

   return str;
  }

  // The URL of the time server we're connecting to
  private string TimeServer;
  private string TimePort;

  public SNTPTimeClient(string host, string port)
  {
   //
   // TODO: 在此處新增建構函式邏輯
   //
   TimeServer = host;
   TimePort=port;
  }

 }
}

呼叫時

SNTPTimeClient client=new SNTPTimeClient(Server,Port);
    client.Connect();    
    string strTest=client.ToString();
    Console.Write(strTest);