/*修改本地時(shí)間*/

intset_local_time(structntp_packet*pnew_time_packet)

{

structtimevaltv;

tv.tv_sec=pnew_time_packet->transmit_timestamp.coarse-JAN_1970;

tv.tv_usec=USEC(pnew_time_packet->transmit_timestamp.fine);

returnsettimeofday(tv,NULL);

}

intmain()

{

intsockfd,rc;

structaddrinfohints,*res=NULL;

structntp_packetnew_time_packet;

memset(hints,0,sizeof(hints));

hints.ai_family=AF_UNSPEC;

hints.ai_socktype=SOCK_DGRAM;

hints.ai_protocol=IPPROTO_UDP;

/*調(diào)用getaddrinfo()函數(shù)，獲取地址信息*/

rc=getaddrinfo(NTP_SERVER_IP,NTP_PORT_STR,hints,res);

if(rc!=0)

{

perror(getaddrinfo);

return1;

}

/*創(chuàng)建套接字*/

sockfd=socket(res->ai_family,res->ai_socktype,res->ai_protocol);

if(sockfd0)

{

perror(socket);

return1;

}

/*調(diào)用取得NTP時(shí)間的函數(shù)*/

if(get_ntp_time(sockfd,res,new_time_packet))

{

/*調(diào)整本地時(shí)間*/

if(!set_local_time(new_time_packet))

{

printf(NTPclientsuccess!n);

}

}

close(sockfd);

return0;

}

為了更好地觀察程序的效果，先用date命令修改一下系統(tǒng)時(shí)間，再運(yùn)行實(shí)例程序。運(yùn)行完了之后再查看系統(tǒng)時(shí)間，可以發(fā)現(xiàn)已經(jīng)恢復(fù)準(zhǔn)確的系統(tǒng)時(shí)間了。具體運(yùn)行結(jié)果如下所示。

$date-s2001-01-011:00:00

2001年01月01日星期一01:00:00EST

$date

2001年01月01日星期一01:00:00EST

$./ntp

NTPclientsuccess!

$date

能夠顯示當(dāng)前準(zhǔn)確的日期和時(shí)間了！