//-------------------------------------------------------------------
//	timedemo.cpp
//
//	This application will attempt to show how the Time Protocol
//	described in RFC-868 may be used to obtain the current time
//	in San Francisco (i.e., Pacific Daylight Time) derived from 
//	Coordinated Universal Time (UTC) reported by a time-server.
//
//		to compile:  $ g++ timedemo.cpp -o timedemo
//		to execute:  $ ./timedemo
//
//	NOTE: This program uses the 'stream-oriented' TCP protocol. 
//
//			-----------------------
//
//	EXERCISE: Find and fix the programming errors in this demo. 
//
//			-----------------------
//
//	programmer: ALLAN CRUSE
//	written on: 18 MAY 2009
//-------------------------------------------------------------------

#include <netdb.h>	// for gethostbyname()
#include <stdio.h>	// for printf(), perror() 
#include <stdlib.h>	// for exit() 
#include <string.h>	// for strcpy()
#include <arpa/inet.h>	// for inet_ntoa()

#define TIME_PORT	123


char hostname[] = "time-nw.nist.gov";


int main( int argc, char **argv )
{
	struct hostent	*hp = gethostbyname( hostname );
	if ( !hp ) { herror( "gethostbyname" ); exit(1); }

	char	hostaddr[ 16 ] = { 0 };
	strcpy( hostaddr, inet_ntoa( *(in_addr*)hp->h_addr ) );
	printf( "\n Time-server is \'%s\' (%s) \n", hostname, hostaddr );

	struct sockaddr_in	saddr = { 0 };
	socklen_t		salen = sizeof( saddr );
	saddr.sin_family	= AF_INET;
	saddr.sin_port		= TIME_PORT;
	saddr.sin_addr.s_addr	= inet_addr( hostaddr );

	int	sock = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );
	if ( sock < 0 ) { perror( "socket" ); exit(1); }

	if ( connect( sock, (sockaddr*)&saddr, salen ) < 0 )
		{ perror( "connect" ); exit(1); }

	unsigned int	since = 0;
	int	rxbytes = recv( sock, &since, sizeof( since ), 0 );
	if ( rxbytes < 0 ) { perror( "recv" ); exit(1); }
	printf( "\n Received %d bytes from server \n", rxbytes );

	unsigned int	utc = htons( since );
	printf( "\n utc = %u seconds \n", utc );

	unsigned int	secs = utc % 60;
	unsigned int	mins = ( utc / 60 ) % 60;
	unsigned int	hour = ( utc / 3600 ) % 24;

	printf( "\n Time now is %02u:%02u:%02u (PST) \n", hour, mins, secs );
	printf( "\n" );	
}