C++ Server Winsock NonBlock

#include <iostream>
#include <fstream>
#include <ws2tcpip.h>
#include <WinSock2.h>

#pragma comment(lib, "ws2_32.lib")

int main() {
    WSADATA wsData;
    WORD ver = MAKEWORD(2, 2);

    if (WSAStartup(ver, &wsData) != 0) {
        std::cerr << "Error starting winsock!" << std::endl;
        return -1;
    }

    SOCKET listenerSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    fcntl( sockfd, F_SETFL, O_NONBLOCK ); // jesli wywala tu blad to zakomentuj

    if (listenerSock == INVALID_SOCKET) {
        std::cerr << "Error creating listener socket! " << WSAGetLastError() << std::endl;
        WSACleanup();
        return -1;
    }

    sockaddr_in listenerHint;
    listenerHint.sin_family = AF_INET;
    listenerHint.sin_port = htons(55000);
    listenerHint.sin_addr.S_un.S_addr = INADDR_ANY;

    bind(listenerSock, (sockaddr*)&listenerHint, sizeof(listenerHint));
    listen(listenerSock, SOMAXCONN);

    sockaddr_in clientHint;
    int clientSize = sizeof(clientHint);

    SOCKET clientSock = accept(listenerSock, (sockaddr*)&clientHint, &clientSize);

    if (clientSock == SOCKET_ERROR) {
        std::cerr << "Error accept socket! " << WSAGetLastError() << std::endl;
        closesocket(listenerSock);
        WSACleanup();
        return -1;
    }

    char host[NI_MAXHOST];
    char serv[NI_MAXSERV];

    if (getnameinfo((sockaddr*)&clientHint, sizeof(clientHint), host, NI_MAXHOST, serv, NI_MAXSERV, 0) == 0) {
        std::cout << "Host: " << host << " connected on port: " << serv << std::endl;
    }
    else {
        inet_ntop(AF_INET, &clientHint.sin_addr, host, NI_MAXHOST);
        std::cout << "Host: " << host << " connected on port: " << ntohs(clientHint.sin_port) << std::endl;
    }

    closesocket(listenerSock);

    const char* welcomeMsg = "Welcome to file server.";
    bool clientClose = false;
    char fileRequested[FILENAME_MAX];
    const int fileAvailable = 200;
    const int fileNotfound = 404;
    const int BUFFER_SIZE = 1024;
    char bufferFile[BUFFER_SIZE];
    std::ifstream file;

    // sending welcome message
    int bysendMsg = send(clientSock, welcomeMsg, strlen(welcomeMsg), 0);

    if (bysendMsg == 0) {
        // error sending data - break loop
        closesocket(clientSock);
        WSACleanup();
        return -1;
    }

    do {
        memset(fileRequested, 0, FILENAME_MAX);
        int byRecv = recv(clientSock, fileRequested, FILENAME_MAX, 0);

        if (byRecv == 0 || byRecv == -1) {
            // error receive data - break loop
            clientClose = true;
        }

        // open file
        file.open(fileRequested, std::ios::binary);

        if (file.is_open()) {
            // file is available
            int bySendinfo = send(clientSock, (char*)&fileAvailable, sizeof(int), 0);
            if (bySendinfo == 0 || bySendinfo == -1) {
                // error sending data - break loop
                clientClose = true;
            }

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

            // send filesize to client
            bySendinfo = send(clientSock, (char*)&fileSize, sizeof(long), 0);
            if (bySendinfo == 0 || bySendinfo == -1) {
                // error sending data - break loop
                clientClose = true;
            }
            file.seekg(0, std::ios::beg);
            // read file with do-while loop
            do {
                // read and send part file to client
                file.read(bufferFile, BUFFER_SIZE);
                if (file.gcount() > 0)
                    bySendinfo = send(clientSock, bufferFile, file.gcount(), 0);

                if (bySendinfo == 0 || bySendinfo == -1) {
                    // error sending data - break loop
                    clientClose = true;
                    break;
                }
            } while (file.gcount() > 0);
            file.close();
        }
        else {
            // Can't open file or file not found
            int bySendCode = send(clientSock, (char*)&fileNotfound, sizeof(int), 0);
            if (bySendCode == 0 || bySendCode == -1) {
                // error sending data - break loop
                clientClose = true;
            }
        }
    } while (!clientClose);

    return 0;
}