How to manage binary files storage in C++

Question

I need to correctly manage binary files streams for copying and pasting compressed files with .zip extension. I'm actually trying to make a simple test project: I would like to copy ./src/Directory.zip in ./dest directory initially empty. The code compiling is correctly done, but at the end of the program the destination directory is still empty and I don't know for which reason. This is the code:

#include <iostream>
#include <fstream>
#include <vector>
typedef unsigned char BYTE;

std::vector<BYTE> readFile(const char* filename)
{
    // open the file:
    std::streampos fileSize;
    std::ifstream file(filename, std::ios::binary);

    // get its size:
    file.seekg(0, std::ios::end);
    fileSize = file.tellg();
    file.seekg(0, std::ios::beg);

    // read the data:
    std::vector<BYTE> fileData(fileSize);
    file.read((char*) &fileData[0], fileSize);
    return fileData;
}

int main(){

    std::vector<BYTE> fileData = readFile("./src/Directory.zip");
    std::ofstream destFile;
    destFile = std::ofstream("./dest/Directory.zip", std::ios::out | std::ios::binary);
    if ( !destFile )
        std::cout << std::strerror(errno) << '\n';
    destFile.write( (char*) &fileData[0], sizeof(BYTE)*fileData.size() );
    destFile.close();
    
    return 0;
}

I know this could be simply done with std::filesystem::copy_file or other high-level functions, but these binary files will be sent through a socket from a server to a client. Firstly I would like to let this work in a local directory.

I've just followed the advice in the answer and I get this error: No such file or directory