通过传时间实现UDP对时

#include <winsock2.h>
#pragma comment(lib,"WS2_32.lib")
WSADATA wsd;
SOCKET s;
char buf[1024];
if(WSAStartup(MAKEWORD(2,2),&wsd)!=0)
{
	return -1;//失败
}
s=socket(AF_INET,SOCK_DGRAM,0);
if(s==INVALID_SOCKET)
{
	WSACleanup();
	return -1;//创建套接字失败
}
SOCKADDR_IN servAddr;
servAddr.sin_family=AF_INET;
servAddr.sin_addr.s_addr=inet_addr("127.0.0.1");
servAddr.sin_port=htons(5000);
if(bind(s,(SOCKADDR*)&servAddr,sizeof(SOCKADDR_IN))==SOCKET_ERROR)
{
	closesocket(s);
	WSACleanup();
	return -1;//绑定套接字失败
}
int nServAddrlen=sizeof(servAddr);
ZeroMemory(buf,sizeof(buf));
if(recvfrom(s,buf,sizeof(buf),0,(SOCKADDR*)&servAddr,&nServAddrlen)==SOCKET_ERROR)
{
	closesocket(s);
	WSACleanup();
	return -1;//接收数据失败
}
CString str(buf);
if(str=="TimeNow")
{
	SOCKADDR_IN clientAddr;
	clientAddr.sin_family=AF_INET;
	clientAddr.sin_addr.s_addr=inet_addr("127.0.0.1");
	clientAddr.sin_port=htons((short)2000);
	int nClientlen=sizeof(clientAddr);
	SYSTEMTIME systime;
	GetLocalTime(&systime);
	if(sendto(s,(char *)&systime,sizeof(SYSTEMTIME),0,(SOCKADDR*)&clientAddr,nClientlen)==SOCKET_ERROR)
	{
		closesocket(s);
		WSACleanup();
		return -1;//向服务器发送数据失败
	}
}
closesocket(s);
WSACleanup();

#include <winsock2.h>
#pragma comment(lib,"WS2_32.lib")
WSADATA wsd;
SOCKET s;
char buf[1024];
if(WSAStartup(MAKEWORD(2,2),&wsd)!=0)
{
	return -1;//失败
}
s=socket(AF_INET,SOCK_DGRAM,0);
if(s==INVALID_SOCKET)
{
	WSACleanup();
	return -1;//创建套接字失败
}
SOCKADDR_IN servAddr;
servAddr.sin_family=AF_INET;
servAddr.sin_addr.s_addr=inet_addr("127.0.0.1");
servAddr.sin_port=htons(2000);
if(bind(s,(SOCKADDR*)&servAddr,sizeof(SOCKADDR_IN))==SOCKET_ERROR)
{
	closesocket(s);
	WSACleanup();
	return -1;//绑定套接字失败
}
int nServAddrlen=sizeof(servAddr);
ZeroMemory(buf,sizeof(buf));
CString ss="TimeNow";
strcpy(buf,ss);
SOCKADDR_IN clientAddr;
clientAddr.sin_family=AF_INET;
clientAddr.sin_addr.s_addr=inet_addr("127.0.0.1");
clientAddr.sin_port=htons((short)5000);
int nClientlen=sizeof(clientAddr);
if(sendto(s,buf,sizeof(buf),0,(SOCKADDR*)&clientAddr,nClientlen)==SOCKET_ERROR)
{
	closesocket(s);
	WSACleanup();
	return -1;//向服务器发送数据失败
}
memset(buf,0,1024);
if(recvfrom(s,buf,sizeof(buf),0,(SOCKADDR*)&servAddr,&nServAddrlen)==SOCKET_ERROR)
{
	closesocket(s);
	WSACleanup();
	return -1;//接收数据失败
}
SYSTEMTIME systime;
memcpy(&systime,buf,16);
SetLocalTime(&systime);//设置本地与服务器时间同步。
closesocket(s);
WSACleanup();