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：

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);}