用来确定路由器的IP地址，也就是在网络上到达特定主机所经过的计算机。
程序需要两个套接字：
1 一个用于接收ICMP封包的原始套接字sRaw
2 用于发送TTL不断增加UDP封包的套接字sSend。
实现代码如下：
代码语言：javascript复制void main()
{
char *szDestIp = "10.16.115.178"; // 210.181.18.12910.16.115.25 61.55.66.30
char recvBuf[1024] = { 0 };
// 创建用于接收ICMP封包的原始套节字，绑定到本地端口
SOCKET sRaw = ::socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
sockaddr_in in;
in.sin_family = AF_INET;
in.sin_port = 0;
in.sin_addr.S_un.S_addr = INADDR_ANY;
if(::bind(sRaw, (sockaddr*)&in, sizeof(in)) == SOCKET_ERROR)
{
printf(" bind() failed n");
return;
}
SetTimeout(sRaw, 5*1000);
// 创建用于发送UDP封包的套节字
SOCKET sSend = ::socket(AF_INET, SOCK_DGRAM, 0);
SOCKADDR_IN destAddr;
destAddr.sin_family = AF_INET;
destAddr.sin_port = ::htons(22);
destAddr.sin_addr.S_un.S_addr = ::inet_addr(szDestIp);
int nTTL = 1;
int nRet;
ICMP_HDR *pICMPHdr;
int nTick;
SOCKADDR_IN recvAddr;
do
{
// 设置UDP封包的TTL值
SetTTL(sSend, nTTL);
nTick = ::GetTickCount();
// 发送这个UDP封包
nRet = ::sendto(sSend, "hello", 5, 0, (sockaddr*)&destAddr, sizeof(destAddr));
if(nRet == SOCKET_ERROR)
{
printf(" sendto() failed n");
break;
}
// 等待接收路由器返回的ICMP报文
int nLen = sizeof(recvAddr);
nRet = ::recvfrom(sRaw, recvBuf, 1024, 0, (sockaddr*)&recvAddr, &nLen);
if(nRet == SOCKET_ERROR)
{
if(::WSAGetLastError() == WSAETIMEDOUT)
{
printf(" time out n");
break;
}
else
{
printf(" recvfrom() failed n");
break;
}
}
// 解析接收到的ICMP数据
pICMPHdr = (ICMP_HDR*)&recvBuf[20]; // sizeof(IPHeader)
if(pICMPHdr->icmp_type != 11 && pICMPHdr->icmp_type != 3 && pICMPHdr->icmp_code != 3)
{
printf(" Unexpected Type: %d , code: %d n",
pICMPHdr->icmp_type, pICMPHdr->icmp_code);
}
else
{
char *szIP = ::inet_ntoa(recvAddr.sin_addr);
printf(" 第%d个路由器，IP地址：%s n", nTTL, szIP);
printf(" 用时：%d毫秒 n", ::GetTickCount() - nTick);
}
if(destAddr.sin_addr.S_un.S_addr == recvAddr.sin_addr.S_un.S_addr)
{
printf("目标可达 n");
break;
}
printf("//------------------------------------// n");
}while(nTTL < 20);
::closesocket(sRaw);
::closesocket(sSend);
}
