SNTP客戶端/日期

Question

可能重複：
Is there any C/C++ library to connect with a remote NTP server?

我在尋找一個在C工作代碼/ C++中獲取時間和日期從服務器（ntp.belnet.be）。它適用於UDP並使用端口123.

有人可以幫忙嗎？

//sending pakket 
memset(&sntp_msg_header, 0, sizeof sntp_msg_header); 
sntp_msg_header.flags = 27; 
sntp_msg_header.originate_timestamp_secs = time(NULL); 

// Get data in rxmsg 
... 
... 

// print time 
timeval = ntohl(rxmsg.transmit_timestamp_secs) - ((70ul * 365ul + 17ul) * 86400ul); 
printf("%s", ctime(&timeval)); 

這是我到目前爲止。但是我無法從中得到正確的數據。 我希望這是更多的信息。

Answer 1

這是linux中的代碼片段。希望這會有所幫助。我不知道如何將其轉換爲C++。

* This code will query a ntp server for the local time and display 
* it. it is intended to show how to use a NTP server as a time 
* source for a simple network connected device. 
* This is the C version. The orignal was in Perl 
* 
* For better clock management see the offical NTP info at: 
* http://www.eecis.udel.edu/~ntp/ 
* 
* written by Tim Hogard (thogard@abnormal.com) 
* Thu Sep 26 13:35:41 EAST 2002 
* Converted to C Fri Feb 21 21:42:49 EAST 2003 
* this code is in the public domain. 
* it can be found here http://www.abnormal.com/~thogard/ntp/ 
* 
*/ 
#include <stdio.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 
#include <arpa/inet.h> 
#include <netdb.h> 
#include <time.h> 
#include <string.h> 

void ntpdate(); 

int main() { 
    ntpdate(); 
    return 0; 
} 

void ntpdate() { 
char *hostname="tick.usno.navy.mil"; 
int portno=123;  //NTP is port 123 
int maxlen=1024;  //check our buffers 
int i;   // misc var i 
unsigned char msg[48]={010,0,0,0,0,0,0,0,0}; // the packet we send 
unsigned long buf[maxlen]; // the buffer we get back 
//struct in_addr ipaddr;  // 
struct protoent *proto;  // 
struct sockaddr_in server_addr; 
int s; // socket 
int tmit; // the time -- This is a time_t sort of 

//use Socket; 
// 
//#we use the system call to open a UDP socket 
//socket(SOCKET, PF_INET, SOCK_DGRAM, getprotobyname("udp")) or die "socket: $!"; 
proto=getprotobyname("udp"); 
s=socket(PF_INET, SOCK_DGRAM, proto->p_proto); 
if(s) { 
    perror("asd"); 
    printf("socket=%d\n",s); 
} 
// 
//#convert hostname to ipaddress if needed 
//$ipaddr = inet_aton($HOSTNAME); 
memset(&server_addr, 0, sizeof(server_addr)); 
server_addr.sin_family=AF_INET; 
server_addr.sin_addr.s_addr = inet_addr(hostname); 
//argv[1]); 
//i = inet_aton(hostname,&server_addr.sin_addr); 
server_addr.sin_port=htons(portno); 
//printf("ipaddr (in hex): %x\n",server_addr.sin_addr); 

/* 
* build a message. Our message is all zeros except for a one in the 
* protocol version field 
* msg[] in binary is 00 001 000 00000000 
* it should be a total of 48 bytes long 
*/ 

// send the data 
printf("sending data..\n"); 
i=sendto(s,msg,sizeof(msg),0,(struct sockaddr *)&server_addr,sizeof(server_addr)); 

// get the data back 
i=recv(s,buf,sizeof(buf),0); 
printf("recvfr: %d\n",i); 
//perror("recvfr:"); 

//We get 12 long words back in Network order 
/* 
for(i=0;i<12;i++) 
    printf("%d\t%-8x\n",i,ntohl(buf[i])); 
*/ 

/* 
* The high word of transmit time is the 10th word we get back 
* tmit is the time in seconds not accounting for network delays which 
* should be way less than a second if this is a local NTP server 
*/ 

tmit=ntohl((time_t)buf[10]); //# get transmit time 
//printf("tmit=%d\n",tmit); 

/* 
* Convert time to unix standard time NTP is number of seconds since 0000 
* UT on 1 January 1900 unix time is seconds since 0000 UT on 1 January 
* 1970 There has been a trend to add a 2 leap seconds every 3 years. 
* Leap seconds are only an issue the last second of the month in June and 
* December if you don't try to set the clock then it can be ignored but 
* this is importaint to people who coordinate times with GPS clock sources. 
*/ 

tmit-= 2208988800U; 
//printf("tmit=%d\n",tmit); 
/* use unix library function to show me the local time (it takes care 
* of timezone issues for both north and south of the equator and places 
* that do Summer time/ Daylight savings time. 
*/ 


//#compare to system time 
printf("Time: %s",ctime(&tmit)); 
i=time(0); 
//printf("%d-%d=%d\n",i,tmit,i-tmit); 
printf("System time is %d seconds off\n",i-tmit); 
}