long IP2Long(std::string &ipString)
{
    long result = 0;
    size_t startPos = 0;
    for ( int ii = 0; ii < 4; ii++ )
    {
        size_t dot = ipString.find('.', startPos);
        int num = ::atoi(ipString.substr(startPos, dot-startPos).c_str());
        result *= 256;
        result += num;
        startPos = dot+1;
    }
    return ::htonl(result);
}