ntpclient.cpp

00001 #include "EthernetNetIf.h"
00002 #include "SimpleSocket.h"
00003 
00004 void ntpclient() {
00005     EthernetNetIf eth;
00006     eth.setup();
00007     
00008     char *NTP_SERVER = "pool.ntp.org";
00009     printf("ntp server = %s\n", NTP_SERVER);
00010 
00011     while (true) {
00012         DatagramSocket datagram;
00013         char buf[48] = {0x23}; // 00100011 LI(0), Version(4), Mode(3: Client)
00014         datagram.write(buf, sizeof(buf));
00015         datagram.send(NTP_SERVER, 123);
00016         
00017         if (datagram.receive() > 0) {
00018             if (datagram.read(buf, sizeof(buf)) > 0) {
00019                 unsigned long seconds = 0;
00020                 for (int i = 40; i <= 43; i++)
00021                     seconds = (seconds << 8) | buf[i];
00022                 set_time(time_t(seconds - 2208988800ULL));
00023                 char timestamp[16];
00024                 time_t jstime = time(NULL) + 9 * 3600;
00025                 strftime(timestamp, sizeof(timestamp), "%m/%d %X", localtime(&jstime));
00026                 printf("Time: %s\n", timestamp);
00027                 break;
00028             }
00029         } else {
00030             printf("no answer\n");
00031             wait(1.0);
00032         }
00033     }
00034 }