Using NTP$\_$Client.c and LocalTime$\_$Client.c examples, create a single program that obtains the current time from NTP and from the local computer. Print both times and print the difference between the two times. On most systems, this should be a very small number as most systems sync their time via NTP$.$ However, the exercise will give you an appreciation of how much local time can slip in between time

synchronization with an external clock.

NTP$\_$client.c

#include

#include

#include

#include

#include

#include

#include

#include

#define NTP$\_$SERVER "pool.ntp$.$org"

#define NTP$\_$PORT $123$

#define NTP$\_$PACKET$\_$SIZE $48$

#define NTP$\_$TIMESTAMP$\_$DELTA $2208988800$ull

typedef struct $\{$

uint$8\_$t li$\_$vn$\_$mode;

uint$8\_$t stratum;

uint$8\_$t poll;

uint$8\_$t precision;

uint$32\_$t root$\_$delay;

uint$32\_$t root$\_$dispersion;

uint$32\_$t reference$\_$id;

uint$32\_$t ref$\_$ts$\_$sec;

uint$32\_$t ref$\_$ts$\_$frac;

uint$32\_$t orig$\_$ts$\_$sec;

uint$32\_$t orig$\_$ts$\_$frac;

uint$32\_$t recv$\_$ts$\_$sec;

uint$32\_$t recv$\_$ts$\_$frac;

uint$32\_$t trans$\_$ts$\_$sec;

uint$32\_$t trans$\_$ts$\_$frac;

$\}$ ntp$\_$packet;

void error$($const char $*$msg$)\{$

perror$($msg$)$;

exit$($EXIT$\_$FAILURE$)$;

$\}$

int main$()\{$

int sockfd, n;

struct sockaddr$\_$in serv$\_$addr;

ntp$\_$packet packet;

sockfd $=$ socket$($AF$\_$INET, SOCK$\_$DGRAM, IPPROTO$\_$UDP$)$;

if $($sockfd $<0)$

error$("$ERROR opening socket"$)$;

memset$($&serv$\_$addr, $0,$ sizeof$($serv$\_$addr$))$;

serv$\_$addr.sin$\_$family $=$ AF$\_$INET;

serv$\_$addr.sin$\_$port $=$ htons$($NTP$\_$PORT$)$;

if $($inet$\_$pton$($AF$\_$INET, NTP$\_$SERVER, &serv$\_$addr.sin$\_$addr$)<=0)$

error$("$ERROR invalid address"$)$;

memset$($&packet, $0,$ sizeof$($packet$))$;

packet.li$\_$vn$\_$mode $=(0$x$03<<6)|(0$x$03<<3)|0$x$03$;

if $($sendto$($sockfd$,$ &packet, sizeof$($packet$),0,($struct sockaddr $*)$&serv$\_$addr, sizeof$($serv$\_$addr$))<0)$

error$("$ERROR sending packet"$)$;

n $=$ recv$($sockfd$,$ &packet, sizeof$($packet$),0)$;

if $($n $<0)$

error$("$ERROR receiving response"$)$;

close$($sockfd$)$;

time$\_$t current$\_$time $=($ntohl$($packet$.$trans$\_$ts$\_$sec$)-$ NTP$\_$TIMESTAMP$\_$DELTA$)$;

printf$("$NTP time: $\%$s$",$ ctime$($t$\_$time$))$;

return $0$;

$\}$

LocalTime$\_$Client.C

#include

#include

int main$()\{$

time$\_$t current$\_$time;

struct tm $*$local$\_$time;

$//$ Get current time

current$\_$time $=$ time$($NULL$)$;

$//$ Convert to local time

local$\_$time $=$ localtime$($t$\_$time$)$;

$//$ Print local time

printf$("$Local time: $\%$s$",$ asctime$($local$\_$time$))$;

return $0$;

$\}$