C# 时间同步 示例源码

【核心代码】

/*
 * NTPClient
 * Copyright (C)2001 Valer BOCAN <vbocan@dataman.ro>
 * Last modified: June 29, 2001
 * All Rights Reserved
 * 
 * This code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY, without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * 
 * To fully understand the concepts used herein, I strongly
 * recommend that you read the RFC 2030.
 * 
 * NOTE: This example is intended to be compiled with Visual Studio .NET Beta 2
 */

namespace TimeSync
{
    using System;
	using System.Net;
	using System.Net.Sockets;
	using System.Runtime.InteropServices;

	// 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>
    /// NTPClient is a C# class designed to connect to time servers on the Internet.
    /// The implementation of the protocol is based on the RFC 2030.
    /// 
    /// 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.
	///	It can also set the system time.
	/// 
	/// 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 NTPClient
    {
		// 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: goto default;
					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: goto default;
					case 6: goto default;
					case 7: goto default;
					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:
						goto case _Stratum.PrimaryReference;
					case _Stratum.PrimaryReference:
						val  = (char)NTPData[offReferenceID   0];
						val  = (char)NTPData[offReferenceID   1];
						val  = (char)NTPData[offReferenceID   2];
						val  = (char)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
									{
									IPHostEntry Host = Dns.GetHostByAddress(Address);
									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
								TimeSpan offspan = TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now);
								val = (time   offspan).ToString();
								break;
							default:
								val = "N/A";
								break;
						}
						break;
				}

				return val;
			}
		}

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

		// Transmit Timestamp
		public DateTime TransmitTimestamp
		{
			get
			{
				DateTime time = ComputeDate(GetMilliSeconds(offTransmitTimestamp));
				// Take care of the time zone
				TimeSpan offspan = TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now);
				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;
		}

		public NTPClient(string host)
        {
			TimeServer = host;
        }

		// Connect to the time server and update system time
		public void Connect(bool UpdateSystemTime)
		{
			try {
				// Resolve server address
				IPHostEntry hostadd = Dns.Resolve(TimeServer);
				IPEndPoint EPhost = new IPEndPoint(hostadd.AddressList[0], 123);
	
				//Connect the time server
				UdpClient TimeSocket = new UdpClient();
				TimeSocket.Connect(EPhost);

				// Initialize data structure
				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);
			  }

			// Update system time
			if(UpdateSystemTime)
			{
				SetTime();
			}
		}

		// 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;
		}

		// SYSTEMTIME structure used by SetSystemTime
		[StructLayoutAttribute(LayoutKind.Sequential)]
		private struct SYSTEMTIME
			{
				public short year;
				public short month;
				public short dayOfWeek;
				public short day;
				public short hour;
				public short minute;
				public short second;
				public short milliseconds;
			}

		[DllImport("kernel32.dll")]
				static extern bool SetLocalTime(ref SYSTEMTIME time);
		

		// Set system time according to transmit timestamp
		private void SetTime()
		{
			SYSTEMTIME st;

			DateTime trts = TransmitTimestamp;
			st.year = (short)trts.Year;
			st.month = (short)trts.Month;
			st.dayOfWeek = (short)trts.DayOfWeek;
			st.day = (short)trts.Day;
			st.hour = (short)trts.Hour;
			st.minute = (short)trts.Minute;
			st.second = (short)trts.Second;
			st.milliseconds = (short)trts.Millisecond;

			SetLocalTime(ref st);
		}

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

    }
}