/////////////////////////////////////////
// simple windows client to be used in 
// adjusting system clock to server clock
// 
// main algorithm:
// James Maxlow
//
// generic socket processes (modified):
// Douglas E. Comer
/////////////////////////////////////////

#include <iostream.h>
#include <fstream.h>
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <winsock.h>
#include <string.h>

void	TCPdaytime(const char *, const char *);
void	errexit(const char *, ...);
SOCKET	connectTCP(const char *, const char *);

#define	LINELEN		 128
#define WSVERS		MAKEWORD(2, 0)


int main(int argc, char *argv[])
{

	char	*host = "localhost";	/* host to use if none supplied	*/
	char	*service = "9090";	/* default service port		*/
	WSADATA wsadata;

	switch (argc) {
	case 1:
		host = "localhost";
		break;
	case 3:
		service = argv[2];
		/* FALL THROUGH */
	case 2:
		host = argv[1];
		break;
	default:
		fprintf(stderr, "usage: TCPdaytime [host [port]]\n");
		exit(1);
	}

	if (WSAStartup(WSVERS, &wsadata) != 0)
		errexit("WSAStartup failed\n");
	TCPdaytime(host, service);
	WSACleanup();


	return 0;	/* exit */
}


void TCPdaytime(const char *host, const char *service)
{

	/////////////////////////////////////////////
	/* used for calculating propagation delays */
	/////////////////////////////////////////////
	double 	propdelays[10];
	double 	sum;
	double 	avgpropdelay;
	double 	maxpropdelay;
	double 	minpropdelay;
	int 	propdelaycount = 15;

	//////////////////////////////////////
	/* client and server time variables */
	//////////////////////////////////////
	double going, coming;		/* for measuring prop delay */
	int dst = 3600;			/* set to 3600 or 0 for d.s.t. */
	int timezonediff = -18000;	/* adjust for local timezone */
	int serverdayportion = 0;	/* server seconds elapsed in current day */
	int settimetohours = 0;		/* correct client time */
	int settimetominutes = 0;	/* correct client time */
	int settimetoseconds = 0;	/* correct client time */
	int settimetomilliseconds = 0;	/* correct client time */

	////////////////////////////////////////////////////////
	/* used to hold server times as strings and long ints */
	////////////////////////////////////////////////////////
	char	messagereply[150];
	char	serversecstring[32];
	char	serverusecstring[32];
	long	serverseclong;
	long	serveruseclong;
	
	int 	i = 0;
	int 	j, k;

	char		buf[LINELEN+1];	/* buffer for one line of text	*/
	SOCKET	s;			/* socket descriptor		*/
	int		cc;			/* recv character count		*/

  	s = connectTCP(host, service);


	///////////////////////////////////////
	/* send message loop for prop delays */
	///////////////////////////////////////
	for (i=0; i<propdelaycount; i++) {

		going = timeGetTime();

		/* send junk message to the server PORT on machine HOST */
		if (send(s, "123", 4, 0) == -1) {
			perror("send");
			exit(1);
		}

	        /* wait for a message to come back from the server */
        	if (recv(s, messagereply, (sizeof(long)*8+3)*2+3, 0) == -1) {
                	perror("recv");
                	exit(1);
        	}
		
		coming = timeGetTime();
		
		propdelays[i] = (double)(coming - going)/2.0;

	} //end prop delay loop


	/////////////////////////////
	/* find prop delay average */
	/////////////////////////////
	sum = 0.0;
	maxpropdelay = 0.0;
	minpropdelay = 99999999999.0;

	for (i=0; i<propdelaycount; i++ ) {
		sum = sum + propdelays[i];
		if (propdelays[i] > maxpropdelay) 
			maxpropdelay = propdelays[i];
		else if (propdelays[i] < minpropdelay)
			minpropdelay = propdelays[i];
	}
	
	avgpropdelay = (sum-maxpropdelay-minpropdelay)/double(propdelaycount-2);	
	

	/////////////////////////////////////////////////////////
	/* now ask server for time in seconds and microseconds */
	/////////////////////////////////////////////////////////
	/* send junk message to the server PORT on machine HOST */
	if (send(s, "123", 3, 0) == -1) {
		perror("send");
		exit(1);
	}

        /* wait for a message to come back from the server */
        if (recv(s, messagereply, 70, 0) == -1) {
                perror("recv");
                exit(1);
        }


	closesocket(s);


	/////////////////////////////
	/* parse server time reply */
	/////////////////////////////
	j = 0;
	while (messagereply[j] != ' ') {

	serversecstring[j]=messagereply[j];
	j++;
	} // end while

	serversecstring[j]='\0';
	
	j = j+3;
	k = 0;
	while (messagereply[j] !='\0') {
	
	serverusecstring[k]=messagereply[j];
	k++; j++;
	} // end while
	
	serverusecstring[k]='\0';
	

	//////////////////////////////////////////////////////////
	/* change server time strings to long ints and break up */
	//////////////////////////////////////////////////////////
	serverseclong = atol(serversecstring);
	serveruseclong = atol(serverusecstring);

	serverdayportion = serverseclong%86400 + timezonediff + dst; 
	if (serverdayportion < 0)
		serverdayportion = serverdayportion + 86400;	/* accout for early morning GMT */

	settimetohours = serverdayportion/3600;
	settimetominutes = (serverdayportion%3600)/60;
	settimetoseconds = serverdayportion%60;
	settimetomilliseconds = serveruseclong/1000.0 + avgpropdelay/1000000.0;


	SYSTEMTIME hey;

	GetSystemTime(&hey);

	hey.wHour = settimetohours;
	hey.wMinute = settimetominutes;
	hey.wSecond = settimetoseconds;
	hey.wMilliseconds = settimetomilliseconds;

	SetSystemTime(&hey);


}