URLDownloadToFile

int Glip(string &Inernet_ip)
{
    Inernet_ip.resize(32);
    TCHAR szTempPath[_MAX_PATH] = {0}, szTempFile[MAX_PATH] = {0};
    string buffer;
    GetTempPath(MAX_PATH, szTempPath);
    UINT nResult = GetTempFileName(szTempPath, _T("~ex"), 0, szTempFile);
    int ret=URLDownloadToFile(NULL,_T("http://www.ip138.com/ip2city.asp"),_T(szTempFile),BINDF_GETNEWESTVERSION,NULL);
    if (ret == S_FALSE)
    {
        return 0;
    }  
    FILE *fp;
    if ((fp = fopen(szTempFile, "rb")) == NULL)
    {
        return 0;
    }
    fseek(fp,0,SEEK_END);//得到文件大小
    int ilength=ftell(fp);
    fseek(fp,0,SEEK_SET);
    if(ilength>0)
    { 
        buffer.resize(ilength);
        fread(&buffer[0],sizeof(TCHAR),ilength,fp);
        fclose(fp);
        DeleteFile(_T("ip.ini"));
        char* str_ip = strstr(&buffer[0], "[");
        if (str_ip !=NULL)
        {
            sscanf(str_ip+1, "%[^]]", &Inernet_ip[0]);
        }     
        return 1;
    }
    else
    {
        fclose(fp);
        return 0;
    }
}

缺少 include 吧，这个是 inet.dll 库的

#pragma comment(lib, "Urlmon.lib")