双管道cmd，清空管道怎么办，谢谢

即是说，传送数据时，连接断开了，而这时管道内还有数据，重连后，cmd还会继续发送管道内的数据，所以想在发送失败时清空管道，而知接退出cmd进程仍存在，请问有那个函数可以清空管道的
。
         while (1) 
{ 
WaitForSingleObject(g_hEvent,INFINITE);
WideCharToMultiByte(m,WC_COMPOSITECHECK,buff,-1,cmidbuff,200,NULL,NULL);
strcat(cmidbuff,("\r\n"));
len=strlen(cmidbuff);
ret=WriteFile(hWritePipe2,cmidbuff,len,&lBytesRead,0); 
if (!ret)
{
break;
}
Sleep(2000);
                  DWORD dwRead;
while(1)
{
memset(buf,0,300);
memset(bufff,0,sizeof(bufff));
ret=PeekNamedPipe(hReadPipe1,buf,300,&lBytesRead,0,0);
if (lBytesRead) 
{ 
ret=ReadFile(hReadPipe1,buf,lBytesRead,&dwRead,0); 
if (!ret)
{
break;
} 
memset((char *)&cmdsend4,0,sizeof(COMMAND));
((DWORD *)cmdsend4.cmdshell)[0]=1;
       MultiByteToWideChar(CP_ACP,0,buf,-1,bufff,dwRead);
memcpy(cmdsend4.cmdshell+4,bufff,sizeof(bufff));
cmdsend4.num=NUM;
cmdsend4.order=CMDPIPE;
memset(objname4,0,LENGTH);
memset(threadrecvbuf,0,REVLEN);
base64Encode((char *)&cmdsend4,objname4,sizeof(COMMAND));
rett=SendCgiRequest(objname4,threadrecvbuf);
if (rett!=3)
{
rett=SendCgiRequest(objname4,threadrecvbuf);
if (rett!=3)
{
break;//发送失败，想请空管道内的数据，该怎么办
}
}
Sleep(200);
}
else
{
memset((char *)&cmdsend4,0,sizeof(COMMAND));
((DWORD *)cmdsend4.cmdshell)[0]=0;
cmdsend4.num=NUM;
cmdsend4.order=CMDPIPE;
memset(objname4,0,LENGTH);
memset(threadrecvbuf,0,REVLEN);
base64Encode((char *)&cmdsend4,objname4,sizeof(COMMAND));
rett=SendCgiRequest(objname4,threadrecvbuf);
if (rett!=3)
{
rett=SendCgiRequest(objname4,threadrecvbuf);
if (rett!=3)
{
break;
}
}
break;
}
}
}