/*******************************************************************************
	Created by Saumit S. Sheth (saumit@execpc.com)
		   April 15, 2003

	This program gets the official date and time from the NIST (ITS) timeserver
	and updates the system time on your computer.

	This program was only tested on Windows 2000 Professional.
*********************************************************************************/

using System;
using System.Drawing;
using System.Net;
using System.Net.Sockets;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;

public class NISTTime
{
	Form mainForm;						// The window that contains everything
	Label timeLabel;					// The label that displays official time
	MainMenu mainMenu;
	MenuItem fileMenu, fileExitMenu, fileGetMenu;		// The file menu and menu items

	public struct SystemTime				// win32 struct
	{
		public short wYear;
		public short wMonth;
		public short wDayOfWeek;
		public short wDay;
		public short wHour;
		public short wMinute;
		public short wSecond;
		public short wMilliseconds;
	};

	[DllImport("kernel32.dll")]				// function imported from kernel32.dll
	public static extern bool SetSystemTime(ref SystemTime systime);
								// win32 API function declaration

	/*----------------------------------------------------------------------
	NISTTime()

	This constructor creates the window, label, and menu objects, and event handlers.
	------------------------------------------------------------------------*/

	public NISTTime()
	{
		mainForm = new Form();
		timeLabel = new Label();
		mainMenu = new MainMenu();
		fileMenu = new MenuItem("File");
		fileExitMenu = new MenuItem("Exit");
		fileGetMenu = new MenuItem("Get Official Time and Update");

		mainForm.Text = "NIST Internet Time Service";	// set title of window
		mainForm.MaximizeBox = false;			// don't need these buttons
		mainForm.MinimizeBox = false;

		timeLabel.Location = new Point(0, 10);		// set position of label
		timeLabel.Width = mainForm.Width - 20;
		timeLabel.Font = new Font("Ariel", 11);		// set label font

		mainMenu.MenuItems.Add(fileMenu);		// create file menu
		fileMenu.MenuItems.Add(fileGetMenu);		// create file menu items
		fileMenu.MenuItems.Add(fileExitMenu);

		fileGetMenu.Click += new EventHandler(this.GetTimeClicked);
								// Add event handler when menu item clicked
		fileExitMenu.Click += new EventHandler(this.ExitClicked);

		mainForm.Controls.Add(timeLabel);		// add objects to window
		mainForm.Menu = mainMenu;
		mainForm.Height = 3 * timeLabel.Height + 20;

		mainForm.ShowDialog();				// display window
	}

	/*----------------------------------------------------------------------
	GetTimeClicked(Object, EventArgs)

	This is the event handler for when the "File->Get Set System Time & Update" menu item is clicked.
	This follows the Daytime Protocol (RFC 867).  Visit www.ietf.org for more information.
	A socket is created to the timeserver IP address at port 13.  I hard-coded the main
	timeserver address, but other timeservers can be used, such as:

	time-a.nist.gov		time-b.nist.gov		utcnist.colorado.edu
	nist1.datum.com		nist1-ny.glassey.com	nist1.aol-ca.truetime.com

	Anything (I just send the "hello" string) can be sent to the timeserver.  What's returned (in ASCII) is:

	JJJJJ YR-MO-DA HH:MM:SS TT L H msADV UTC(NIST) OTM

	where JJJJJ is the Modified Julian Date, YR-MO-DA is the date, HH:MM:SS is the time,
	TT is a 2-digit indicator whether it is ST(00) or DST(50), L is whether a leap second will be added or subtracted
	at the end of the current month, H indicates health of server, msADV is num of ms NIST advances to compensate for
	network delays, UTC is a label always included, OTM is the on-time-marker, an '*'.
	Once the data is received, the socket is closed.  The information is parsed and a label displays the information.
	The SetSystemTime API function is called and the system time is updated.
	-------------------------------------------------------------------------*/

	private void GetTimeClicked(Object sender, EventArgs e)
	{
		DateTime official, localtime;			// official time from timeserver, localtime version
		string returndata = null;			// bytes returned from timeserver
		string[] dates = new string[4];			// year, month, day
		string[] times = new string[4];			// hour, minute, second
		string[] tokens = new string[11];		// bytes tokenized

		TcpClient tcpclient = new TcpClient();		// create new socket object

		try
		{
			tcpclient.Connect("time.nist.gov", 13);	// try to connect to timeserver

			NetworkStream networkStream = tcpclient.GetStream();
								// socket stream

			if (networkStream.CanWrite && networkStream.CanRead)
								// stream is ready
			{
				Byte[] sendBytes = Encoding.ASCII.GetBytes("Hello");
								// the hello string, Can be anything!
				networkStream.Write(sendBytes, 0, sendBytes.Length);
								// send to timeserver
      	
				byte[] bytes = new byte[tcpclient.ReceiveBufferSize];
				networkStream.Read(bytes, 0, (int) tcpclient.ReceiveBufferSize);
								// the official timeserver data  
				returndata = Encoding.ASCII.GetString(bytes);
								// cast as ASCII string
			}

			tcpclient.Close();			// close socket
		}
		catch(Exception excep)
		{
			MessageBox.Show(excep.ToString());	// display exception to user
			return;					// if exception occurred don't continue
		}

		tokens = returndata.Split(' ');			// the timeserver data space parsed
		dates = tokens[1].Split('-');			// the date info hypen parsed
		times = tokens[2].Split(':');			// the time info colon parsed

		official = new DateTime(Int32.Parse(dates[0]) + 2000, Int32.Parse(dates[1]), Int32.Parse(dates[2]),
					Int32.Parse(times[0]), Int32.Parse(times[1]), Int32.Parse(times[2]));
								// create a new datetime object with these values

		localtime = TimeZone.CurrentTimeZone.ToLocalTime(official);
								// UTC converted to computer's time zone
		timeLabel.Text = localtime.ToLongDateString() + "  " + localtime.ToLongTimeString();
								// display official date and time

		SystemTime systime = new SystemTime();		// create systemtime object

		systime.wYear = (short)official.Year;		// set struct with correct values
		systime.wMonth = (short)official.Month;
		systime.wDay = (short)official.Day;
		systime.wHour = (short)official.Hour;
		systime.wMinute = (short)official.Minute;
		systime.wSecond = (short)official.Second;

		SetSystemTime(ref systime);			// win32 API function to set system time (in UTC)
	}

	/*----------------------------------------------------------------------
	ExitClicked(Object, EventArgs)

	This event handler halts the program and quits.
	------------------------------------------------------------------------*/

	private void ExitClicked(Object sender, EventArgs e)
	{
		Application.Exit();				// Quit program
	}

	/*----------------------------------------------------------------------
	Main(string[])

	The entrypoint of the program
	------------------------------------------------------------------------*/

	public static void Main(string[] args)
	{
		NISTTime nisttime = new NISTTime();		// Create new instance of object
	}
}