gethostbyaddr()扫描不存在IP时的等待时间可否改变？

Question

gethostbyaddr()扫描不存在IP时的等待时间可否改变？第三个参数有哪些取值？

Answer 1

我的思路是：用gethostbyaddr()扫描局域网IP，通过gethostbyaddr()对指定的IP进行探测，若返回值为NULL，则说明该IP不存在，否则,将该IP添加到列表框中，在探测下一个IP.
但是如果该IP不存在，整个程序要等几十秒才能开始探测下一个IP，我能不能自己控制gethostbyaddr()的等待时间，比如说0.2秒后无反应就探测下一个IP。

Answer 2

gethostbyaddr() 如何调整超时我不知道, 想来也不是很方便, 倒不如考虑考虑建一个表, 然后一次扫描一批IP地址, 等待返回即可.时间和效率上恐怕都要比你的 0.2 秒要好.

Answer 3

类似ping命令，我下面有个程序，是多线程的。你看看
开始扫描
UINT PingThread( LPVOID pParam )
{
CPingThreadInfo* pThreadInfo = (CPingThreadInfo*)pParam;
HWND m_hWnd = pThreadInfo->m_hwndNotifyWnd;

SOCKET   rawSocket;
struct    sockaddr_in saDest;
struct    sockaddr_in saSrc;
unsigned int tempIP=0;
int nRet;
DWORD   dwTimeSent,dwElapsed;
u_char    cTTL;
LPHOSTENT lpHost;
HOSTENT HostInfo;
int nZoneID=0;

WORD wVersionRequested;

WSADATA wsaData;
int err;

wVersionRequested = MAKEWORD( 2, 2 );

err = WSAStartup( wVersionRequested, &wsaData );

rawSocket = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);

tempIP=pThreadInfo->uintIP[0];
pThreadInfo->nRetries=1;
while (tempIP<=pThreadInfo->uintIP[1])
{
if (WaitForSingleObject(pThreadInfo->m_hEventKillPing,0)== WAIT_OBJECT_0)
break;
saDest.sin_addr.S_un.S_addr =htonl(tempIP);
unsigned int ip1=0,ip2=0;
ip2=htonl(tempIP);
saDest.sin_family = AF_INET;
saDest.sin_port = 0;
for (int nLoop = 0; nLoop < pThreadInfo->nRetries; nLoop++)
{
if (WaitForSingleObject(pThreadInfo->m_hEventKillPing,0)== WAIT_OBJECT_0)
break;
// Send ICMP echo request
SendEchoRequest(rawSocket, &saDest);
::PostMessage(pThreadInfo->m_hwndNotifyWnd,WM_MSG_SEARCH_DISPLAY,0,(LPARAM)ip2);
nRet=WaitForEchoReply(rawSocket);
if (!nRet)
{
}
else
{
if (WaitForSingleObject(pThreadInfo->m_hEventKillPing,0)== WAIT_OBJECT_0)
break;
// Receive reply
dwTimeSent = RecvEchoReply(rawSocket, &saSrc, &cTTL);
// Calculate elapsed time
dwElapsed = GetTickCount() - dwTimeSent;
::PostMessage(pThreadInfo->m_hwndNotifyWnd,WM_MSG_SEARCH_FIND,0,(LPARAM)ip2);
//
}
::Sleep(20);
}
tempIP++;

}
nRet = closesocket(rawSocket);

WSACleanup();
::PostMessage(pThreadInfo->m_hwndNotifyWnd,WM_MSG_SEARCH_PINGSTOP,0,0);
return 1;
}typedef struct CPingThreadInfo
{
//IP Zone
unsigned int uintIP[2];
//Retry count
int nRetries;
int nThreshold;
HANDLE m_hEventKillPing;
HWND m_hwndNotifyWnd;
} CPingThreadInfo;
下面是调用的过程         CPingThreadInfo m_ThreadInfo; UpdateData(true); m_ipfrom.GetAddress(ipfrom);
m_ipto.GetAddress(ipto);
if(ipfrom > ipto)
{
AfxMessageBox("Input error!");
return;
}
m_ThreadInfo.uintIP[0]=ipfrom;
m_ThreadInfo.uintIP[1]=ipto;
m_ThreadInfo.m_hwndNotifyWnd = this->GetSafeHwnd();
m_Thread= AfxBeginThread(PingThread,&m_ThreadInfo);结束扫描SetEvent(m_ThreadInfo.m_hEventKillPing);如果好用就给分，马上到3个角了：），赚点分