114 lines
2.5 KiB
C
114 lines
2.5 KiB
C
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#pragma once
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#ifndef _WIN32
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#include <unistd.h>
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#include <netdb.h>
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#include <netinet/in.h>
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#include <sys/socket.h>
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#define INVALID_SOCKET (-1)
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#define SOCKET int
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#define SOCKET_ERROR (-1)
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#define closesocket close
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#endif
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#include <time.h>
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class NTPClient
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{
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public:
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static time_t GetCurrentTimeUTC(const char * ntpserver = NULL)
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{
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#ifdef _WIN32
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WSADATA w;
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int remote_length;
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#else
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socklen_t remote_length;
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#endif
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SOCKET sd = INVALID_SOCKET;
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char ntp_buffer[48];
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time_t current_time = 0;
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struct hostent *hp;
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struct sockaddr_in remote;
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struct sockaddr_in local;
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char host_name[256];
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hostent * host = NULL;
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do {
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#ifdef _WIN32
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if (WSAStartup(MAKEWORD(2, 2), &w) != 0)
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return 0;
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#endif
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if ((sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == INVALID_SOCKET)
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break;
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memset((void *)&remote, '\0', sizeof(struct sockaddr_in));
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remote.sin_family = AF_INET;
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remote.sin_port = htons(123);
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if ((host = gethostbyname((ntpserver) ? ntpserver : "time.windows.com")) == NULL)
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break;
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remote.sin_addr.s_addr = *(u_long *)host->h_addr_list[0];
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memset((void *)&local, '\0', sizeof(local));
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local.sin_family = AF_INET;
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local.sin_port = htons(0);
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local.sin_addr.s_addr = htonl(INADDR_ANY);
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if (::bind(sd, (struct sockaddr *)&local, sizeof(local)) == SOCKET_ERROR)
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break;
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memset(ntp_buffer, 0, sizeof(ntp_buffer));
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ntp_buffer[0] = 0x1B;
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remote_length = sizeof(struct sockaddr_in);
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if (sendto(sd, ntp_buffer, sizeof(ntp_buffer), 0, (struct sockaddr *)&remote, remote_length) == -1)
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break;
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fd_set fds;
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FD_ZERO(&fds);
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FD_SET(sd, &fds);
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timeval timeout;
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timeout.tv_sec = 10;
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timeout.tv_usec = 0;
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if (select(1, &fds, NULL, NULL, &timeout) != 1)
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break;
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if (recvfrom(sd, ntp_buffer, sizeof(ntp_buffer), 0, (struct sockaddr *)&remote, &remote_length) < 0)
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break;
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unsigned int int_part = *(unsigned int *)(ntp_buffer + 40);
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unsigned int fract_part = *(unsigned int *)(ntp_buffer + 44);
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int_part = SwapEndianness(int_part);
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current_time = (time_t)(int_part -= 2208988800U);
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}
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while (0);
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if (sd != INVALID_SOCKET)
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closesocket(sd);
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#ifdef _WIN32
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WSACleanup();
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#endif
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return current_time;
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}
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static unsigned int SwapEndianness(unsigned int x)
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{
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return (unsigned int)(((x & 0x000000ff) << 24) +
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((x & 0x0000ff00) << 8) +
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((x & 0x00ff0000) >> 8) +
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((x & 0xff000000) >> 24));
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}
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};
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