Need help using Wininet Functions

I am programming in C++ and I want to upload a file to my web server which i have already done using the following code:

#include "stdafx.h"
#include <windows.h>
#include <wininet.h>
#pragma comment(lib, "wininet")


int _tmain(int argc, _TCHAR* argv[])
{
HINTERNET hInternet;
HINTERNET hFtp;

hInternet = InternetOpen(NULL, INTERNET_OPEN_TYPE_DIRECT, NULL,NULL,0);
hFtp = InternetConnect(hInternet, L"ftp.freetzi.com", INTERNET_DEFAULT_FTP_PORT, L"myuser.freetzi.com", "mypassword", INTERNET_SERVICE_FTP, 0, 0);

FtpPutFile(hFtp, L"C:\\deneme.txt", L"coolName.txt", FTP_TRANSFER_TYPE_BINARY, 0);

if ( FtpPutFile(hFtp, L"C:\\deneme.txt", L"coolName.txt", FTP_TRANSFER_TYPE_BINARY, 0) )
{
    MessageBox(NULL, L"Upload Successful.", L"Title", NULL);
}
else
{
            //This is the message I get...
    MessageBox(NULL, L"Upload Failed.", L"Title", NULL);
}


InternetCloseHandle(hFtp);
InternetCloseHandle(hInternet);


return 0;
}

But as this program will be used by many people, I can't find a way to rename the uploaded file coolname.txt if the target file already exists, the code above will overwrite the old data and rewrite the new one of used 2 or more times,

I tried:

"/public_html/log.txt" + std::to_string(rand())

2 . A function :-

generateFileName( std::string const& directory, std::string const& rootName, std::string const& extension ) { std::ostringstream results; results.fill( '0' ); results << directory << '/' << rootName << '-' << std::setw(4) << rand() << extension; return results.str(); }

I however, found a way to accomplish this task using FtpFindFirstFile But I am unable to know how to use it. If someone could explain me more clear or give some examples, I would really appriciate.

Reference : http://msdn.microsoft.com/en-us/library/windows/desktop/aa384180(v=vs.85).aspx

you can define the Output File name as variable.

#include <iostream>
#include <string>
#include <stdio.h>
#include <time.h>

// Get current date/time, format is YYYY-MM-DD.HH:mm:ss
const std::string currentDateTime() {
    time_t     now = time(0);
    struct tm  tstruct;
    char       buf[80];
    tstruct = *localtime(&now);
    // Visit http://en.cppreference.com/w/cpp/chrono/c/strftime
    // for more information about date/time format
    strftime(buf, sizeof(buf), "%Y-%m-%d.%X", &tstruct);

    return buf;
}

int main() {
    std::cout << "currentDateTime()=" << currentDateTime() << std::endl;
    getchar();  // wait for keyboard input
}

Define a file name as variable , in which we have to append current timestamp with filename.

Finally your file name will be "coolName_2014.06.25.07.08.08.txt"

I hope this will help you.