#include <stdio.h>#include <sys/types.h>#include <sys/fcntl.h>#include <sys/socket.h>#include <netinet/in.h>#include <netdb.h>#include <errno.h>#include <string.h>#include <unistd.h>#include <wait.h>#include <signal.h>#include <pthread.h>#include <time.h>#include <arpa/inet.h>#define TIME_PORT  123#define MAXLINE    255#define MAX_SNTP_SERVER  3typedef struct{  unsigned int Seconds;		/* Since 00:00:00 Jan 01 1900 */  unsigned int Fraction;} NTP_TIMESTAMP;typedef struct{  char Control;  char Stratum;  char Poll;  char Precision;  unsigned int RootDelay;  unsigned int RootDispersion;  unsigned int ReferenceIdentifier;  NTP_TIMESTAMP ReferenceTimestamp;  NTP_TIMESTAMP OriginateTimestamp;  NTP_TIMESTAMP ReceiveTimestamp;  NTP_TIMESTAMP TransmitTimestamp;  unsigned int KeyIdentifier;	/* Optional */  char MessageDigest[16];	/* Optional */} NTP_PACKET;#define NTP_PACKET_MINLEN       48	/* Packet size - optional fields */#define NTP_LI_NOLEAP           0x00#define NTP_LI_61SECS           0x40#define NTP_LI_59SECS           0x80#define NTP_LI_ALARM            0xC0#define NTP_VERSION_GET(pkt)    ((((pkt)->Control)>>3)&0x7)#define NTP_VERSION_SET(ver)    (((ver)&0x7)<<3)#define NTP_MODE_RESERVED       0#define NTP_MODE_SYMACTIVE      1	/* Symmetric Active */#define NTP_MODE_SYMPASSIVE     2	/* Symmetric Passive */#define NTP_MODE_CLIENT         3#define NTP_MODE_SERVER         4#define NTP_MODE_BROADCAST      5#define NTP_MODE_NTPCTRL        6	/* Reserved for NTP control message */#define NTP_MODE_PRIVATE        7	/* Reserved for private use */#define NTP_MODE_GET(pkt)       (((pkt)->Control)&0x7)#define NTP_MODE_SET(mode)      ((mode)&0x7)#define TIME_BASEDIFF           ((((unsigned int)70*365 + 17) * 24*3600))#define TIME_NTP_TO_LOCAL(t)	((t)-TIME_BASEDIFF)#define TIME_LOCAL_TO_NTP(t)	((t)+TIME_BASEDIFF)struct sntp_srv_s{  struct sockaddr_in addr;  int stratum;  int version;  unsigned int timestamp;};#define SNTP_WAITPERIOD        10 	/* Wait period in seconds */#define SNTP_UPDATEPERIOD      (30*60)	/* Update period in seconds */