我参考的是这篇文章：http://www.fetia.cn/2010/07/4728.html
写成Delphi的，Sendto 错误。
请各位大大指点。
unit Unit2;
interface
uses Windows,Winsock2,SysUtils;
type
NTPPACKET=record
li,vn,mode,stratum,poll,precision:uint8;
root_delay,root_dispersion:ulong32;
ref_id:array[0..3] of uint8;
reftimestamphigh,reftimestamplow,oritimestamphigh,
oritimestamplow,recvtimestamphigh,recvtimestamplow,
trantimestamphigh,trantimestamplow:ulong32;
end;

function getntptime:_SYSTEMTIME;
implementation
function getntptime:_SYSTEMTIME;
var
WSAData:TWSAData;
skt:TSocket;
addr:TSockAddrIn;
recbuf:array[0..255] of Char;
n:integer;
ntppack:NTPPACKET;
firsttime:Cardinal;
tt:TDateTime;
begin
WSAStartup($0101,WSAData);
skt:=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
if skt<0then
begin
Exit;
end;
ZeroMemory(@ntppack,SizeOf(ntppack));
ntppack.li :=0;
ntppack.vn :=3;
ntppack.mode :=3;
ntppack.stratum :=2;
firsttime:=DateTimeToFileDate(now);
ntppack.oritimestamphigh:=htonl(firsttime);
ZeroMemory(@addr,SizeOf(PSockAddr));
addr.sin_family :=AF_INET;
addr.sin_port:=htons(13);
addr.sin_addr.S_addr:=inet_addr('stdtime.gov.hk');
addr.sin_zero :=#0;
if sendto(skt,ntppack,SizeOf(ntppack),0,@addr,SizeOf(addr))>0 then //这样写对吗？
begin
FillChar(recbuf,sizeof(recbuf),#0);
recv(skt,recbuf,sizeof(recbuf),n);
end;
WSACleanup;
closesocket(skt);
end;
end.

'stdtime.gov.hk' 这个服务器用Indy 的IdDayTime控件试过，用的是13的端口，可以正确取到时间值。
但是查资料好像都说NTP使用的是：123专用端口。

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The empty vessels make the greatest sound.