sd = WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, 0, 0, 0);

//初试化RAW Socket, 设置ttl, 初试化dest
// 返回值 <0 表失败

int setup_for_ping(char* host, int ttl, SOCKET& sd, sockaddr_in& dest)
{
    // Create the socket
    sd = WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, 0, 0, 0);
    if (sd == INVALID_SOCKET) {
        cerr << "Failed to create raw socket: " << WSAGetLastError() <<
                endl;
        return -1;
    }

    if (setsockopt(sd, IPPROTO_IP, IP_TTL, (const char*)&ttl, 
            sizeof(ttl)) == SOCKET_ERROR) {
        cerr << "TTL setsockopt failed: " << WSAGetLastError() << endl;
        return -1;
    }

    // Initialize the destination host info block
    memset(&dest, 0, sizeof(dest));

    // Turn first passed parameter into an IP address to ping
    unsigned int addr = inet_addr(host);
    if (addr != INADDR_NONE) {
        // It was a dotted quad number, so save result
        dest.sin_addr.s_addr = addr;
        dest.sin_family = AF_INET;
    }
    else {
        // Not in dotted quad form, so try and look it up
        hostent* hp = gethostbyname(host);
        if (hp != 0) {
            // Found an address for that host, so save it
            memcpy(&(dest.sin_addr), hp->h_addr, hp->h_length);
            dest.sin_family = hp->h_addrtype;
        }
        else {
            // Not a recognized hostname either!
            cerr << "Failed to resolve " << host << endl;
            return -1;
        }
    }

    return 0;
}