//非正常回复
　　if (icmphdr->type != ICMP_TTL_EXPIRE)
　　{
　　　//ttl减为零
　　　if (icmphdr->type == ICMP_DEST_UNREACH)
　　　{
　　　　//主机不可达
　　　　cerr << "Destination unreachable" << endl;
　　　}
　　　else
　　　{
　　　　//非法的ICMP包类型
　　　　cerr << "Unknown ICMP packet type " << int(icmphdr->type) <<" received" << endl;
　　　}
　　　return - 1;
　　}
　}
　else if (icmphdr->id != (unsigned short)GetCurrentProcessId())
　{
　　//不是本进程发的包, 可能是同机的其它ping进程发的
　　return - 2;
　}

　// 指出往返时间TTL
　int nHops = int(256-reply->ttl);
　if (nHops == 192)
　{
　　// TTL came back 64, so ping was probably to a host on the
　　// LAN -- call it a single hop.
　　nHops = 1;
　}
　else if (nHops == 128)
　{
　　// Probably localhost
　　nHops = 0;
　}

　// 输出信息
　cout << endl << bytes << " bytes from " << inet_ntoa(from->sin_addr) <<", icmp_seq " << icmphdr->seq << ", ";
　if (icmphdr->type == ICMP_TTL_EXPIRE)
　{
　　cout << "TTL expired." << endl;
　}
　else
　{
　　cout << nHops << " hop" << (nHops == 1 ? "" : "s");
　　cout << ", time: " << (GetTickCount() - icmphdr->timestamp) << " ms." <<endl;
　}
　return 0;
}

　　为了在Visual C++中更加方便地使用发送和接收ICMP报文，我们可以使用由Jay Wheeler编写的CIcmp（An ICMP Class For MFC）类，在著名的开发网站的如下地址可以下载。

　　这个类的简要框架如下：

class CIcmp: public CSocket
{
　// Attributes
　public:
　　BOOL OpenNewSocket(HWND hWnd, unsigned int NotificationMessage, long NotifyEvents);
　　BOOL OpenNewSocket(HWND hWnd, unsigned int NotificationMessage, long NotifyEvents, int AFamily, int AType, int AProtocol);
　　int CloseIcmpSocket(void);
　　BOOL Connect(int ReceiveTimeout, int SendTimeout);
　　BOOL Connect(LPINT ReceiveTimeout, LPINT SendTimeout, int AFamily, int AType, int AProtocol);
　　int SetTTL(int TTL);
　　int SetAsynchNotification(HWND hWnd, unsigned int Message, long Events);
　　int Receive(LPSTR pIcmpBuffer, int IcmpBufferSize);
　　unsigned long GetIPAddress(LPSTR iHostName);
　　int Ping(LPSTR pIcmpBuffer, int IcmpBufferSize);
　　unsigned short IcmpChecksum(unsigned short FAR *lpBuf, int Len);
　　void DisplayError(CString ErrorType, CString FunctionName);

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