ntp.rar_NTP协议分析_ntp_ntp对时_ntp网络校时

//先来个NTP协议介绍 //http://blog.163.com/yzc_5001/blog/static/2061963420121283050787/ //关于时间戳的换算工具 //http://tool.chinaz.com/Tools/unixtime.aspx# //下面是代码，C-Free + MinGW 编译，须在工程连接参数里添加 -lwsock32 #include <stdio.h> #include <time.h> #include <winsock2.h> #define JAN_1970 0x83AA7E80 /* 2208988800 1970-1900 in seconds*/ typedef union { int time; char time_array[4]; } Timestamp; typedef struct { char message_hdr[16];//报文头部 char RefTimestamp[8]; Timestamp T1; char T1_decimal[4]; //T1的小数部分 Timestamp T2; char T2_decimal[4]; //T2的小数部分 Timestamp T3; char T3_decimal[4]; //T3的小数部分 } NTP_MESSAGE; int main() { WORD socketVersion = MAKEWORD(2,2); WSADATA wsaData; if(WSAStartup(socketVersion, &wsaData) != 0) { return 0; } SOCKET sclient = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); SOCKADDR_IN sin; sin.sin_family = AF_INET; sin.sin_port = htons(123); sin.sin_addr.S_un.S_addr = inet_addr("198.123.30.132"); int len = sizeof(sin); char sendData[] = { //构造报文 0x1B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xD0, 0xAF, 0x5F, 0xF5, 0x23, 0xD7, 0x08, 0x00 }; printf("Connect to NTP Server...\n"); time_t T1=time(NULL); sendto(sclient, sendData, sizeof(sendData), 0, (SOCKADDR *)&sin, len); char recvData[48]={0}; int ret = recvfrom(sclient, recvData, 48, 0, (SOCKADDR *)&sin, &len); if(ret > 0) { time_t T4=time(NULL); printf("Connect success!\n\n"); printf("Now the local time is %s",ctime(&T4)); NTP_MESSAGE *ntp_time=(NTP_MESSAGE *)recvData; /* 大小端变换 由于NTP以1900为始，需变换 */ ntp_time->T2.time=ntohl(ntp_time->T2.time)-JAN_1970;//T2 ntp_time->T3.time=ntohl(ntp_time->T3.time)-JAN_1970;//T3 /* NTP报文的网络延时=（T4-T1）-（T3-T2） */ time_t net_delay=(T4-T1)-(ntp_time->T3.time-ntp_time->T2.time); printf("Net delay is %ld second(s).\n",net_delay); /* 误差补偿秒数=（（T2-T1）+（T3-T4））/2 */ time_t Deviation=(((time_t)ntp_time->T2.time-T1)+((time_t)ntp_time->T3.time-T4))/2; printf("\nThe deviation is %d second(s).\n",Deviation); if(Deviation != 0) { printf("Reset the local time...\n"); time_t now=time(NULL)+Deviation; struct tm *ptr; ptr=localtime(&now); char buffer[20]={0}; sprintf(buffer,"date %d-%d-%d",ptr->tm_year+1900,ptr->tm_mon+1,ptr->tm_mday); system(buffer); sprintf(buffer,"time %d:%d:%d",ptr->tm_hour,ptr->tm_min,ptr->tm_sec); system(buffer); now=time(NULL); printf("Now the local time is %s",ctime(&now)); } else //没有误差，无需校时 { printf("Here is no need to set local time.\n"); } } closesocket(sclient); WSACleanup(); system("pause"); return 0; }