sample

#include <stdio.h>
#include <winsock2.h>
#include <string>
#include <iostream>
#include <fstream>
#include <stdlib.h>

#pragma comment(lib, "ws2_32.lib") //Winsock Library

using namespace std;

int main() {
    cout << "Connecting to port...";
    unsigned short int s_port;
    cout << "Enter server port: ";
    cin >> s_port;
    cout << "OK. Port: " << s_port << endl;


    cout << "Initialization...";
    WSADATA wsaData;
    int res = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (res != NO_ERROR)
        cout << "ERROR. " << WSAGetLastError() << endl;
    cout << "OK. Initialized" << endl;

    cout << "Creating socket...";
    SOCKET clientSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (clientSocket == INVALID_SOCKET) {
        cout << "ERROR. Invalid socket!" << endl;
        return 0;
    }
    cout << "OK. Socket created." << endl;



    cout << "Binding...";
    struct sockaddr_in client;
    client.sin_family = AF_INET;
    client.sin_port = htons(s_port);
    client.sin_addr.s_addr = inet_addr("10.0.1.3");
    int clientSize = sizeof(client);

    if (bind(clientSocket, (struct sockaddr*) &client, clientSize) == SOCKET_ERROR) {
        cout << "ERROR. Binding not completed!" << endl;
    }
    cout << "OK. Socket binded" << endl;

    const int part_size = 1024;
    char *FilenameBuffer = new char[part_size];

    while (1) {
        memset(FilenameBuffer, '\0', part_size);

        cout << "Trying to recieve data...";
        int recv_len;
        if ((recv_len = recvfrom(clientSocket, FilenameBuffer, part_size, 0, (struct sockaddr *) &client, &clientSize)) == SOCKET_ERROR) {
            cout << "ERROR. Recvfrom() failed" << endl;
            return 0;
        }
        cout << "New client connected!" << endl;
        cout << "Received filename from " << inet_ntoa(client.sin_addr) << " : " << ntohs(client.sin_port) << endl;
        cout << "Bytes Recv: " << recv_len << endl;
        cout << "Recieved data (filename): " << FilenameBuffer << endl;

        cout << "transfer???????" << endl;

        struct stat si;
        if (stat(FilenameBuffer, &si)) {
            perror("stat");
            if (sendto(clientSocket, "File not found", 15, 0, (struct sockaddr *)&client, clientSize) == SOCKET_ERROR) {
                cout << "ERROR. Sending error!" << endl;
                return 0;
            }
            return 0;
        }

        cout << "Si: " << si.st_size << endl;
        string tmp = stoi(si.st_size);
        cout << "Si size: " << tmp.length() << endl; //????????

        char *buf = new char[temp.length()];
        char tmp[part_size];
        buf = itoa(si.st_size, tmp, 10);


        int t = sendto(clientSocket, buf2, temp.length(), 0, (struct sockaddr *)&client, clientSize);
        if (t == SOCKET_ERROR) {
            cout << "ERROR. Sending file size error!" << endl;
            return 0;
        }
        cout << "OK. " << inet_ntoa(client.sin_addr) << " send bytes " << t << " by " << t << endl;

        int parts_count = si.st_size / part_size;
        int last_part_size = si.st_size % part_size;

        cout << "Parts_count: " << parts_count << endl << "Last_part_size: " << last_part_size << endl; //?????????

        FILE *file;

        if ((file=fropen(FilenameBuffer, "rb")) == NULL) {
            cout << "ERROR. Open file error!" << endl;
            if (sendto(clientSocket, "File not found", 15, 0, (struct sockaddr *)&client, clientSize) == SOCKET_ERROR) {
                cout << "ERROR. Sending error!" << endl;
                return 0;
            }
            return 0;
        } else {
            char *buffer = new char[part_size];

            for (int i = 0; i < parts_count; i++) {
                memset(buffer, '\0', part_size);
                if (fread(buffer, 1, part_size, file) != part_size) {
                    cout << "ERROR. Fread error!" << endl;
                    return 0;
                }
                if (sendto(clientSocket, buffer, part_size, 0, (struct sockaddr *) &client, clientSize) == SOCKET_ERROR) {
                    cout << "ERROR. Sending file error!" << endl;
                }
                Sleep(1); //?????
            }

            if (last_part_size) {
                if (fread(buffer, 1, last_part_size, file) != last_part_size) {
                    cout << "ERROR. Fread error!" << endl;
                    return 0;
                }
                if (sendto(clientSocket, buffer, last_part_size, 0, (struct sockaddr *) &client, clientSize) == SOCKET_ERROR) {
                    cout << "ERROR. Fread error!" << endl;
                    return 0;
                }
            }
            delete[] buffer;
            fclose(f);
        }
        cout << "End of sending file." << endl;
    }
    closesocket(clientSocket);
    WSACleanup();
    cout << "Socket closed! End of program working." << endl;
    return 0;
}