ntpclient.cpp

00001 #include "SimpleSocket.h"
00002 
00003 void ntpclient() {
00004     char *NTP_SERVER = "pool.ntp.org";
00005     printf("ntp server = %s\n", NTP_SERVER);
00006 
00007     while (true) {
00008         DatagramSocket datagram;
00009         char buf[48] = {0x23}; // 00100011 LI(0), Version(4), Mode(3: Client)
00010         datagram.write(buf, sizeof(buf));
00011         datagram.send(NTP_SERVER, 123);
00012         
00013         //datagram.setTimeout(5.0);
00014         if (datagram.receive() > 0) {
00015             if (datagram.read(buf, sizeof(buf)) > 0) {
00016                 unsigned long seconds = 0;
00017                 for (int i = 40; i <= 43; i++)
00018                     seconds = (seconds << 8) | buf[i];
00019                 set_time(time_t(seconds - 2208988800ULL));
00020                 char timestamp[16];
00021                 time_t jstime = time(NULL) + 9 * 3600;
00022                 strftime(timestamp, sizeof(timestamp), "%m/%d %X", localtime(&jstime));
00023                 printf("Time: %s\n", timestamp);
00024                 break;
00025             }
00026         } else {
00027             printf("no answer\n");
00028             wait(1.0);
00029         }
00030     }
00031 }