ServerUDPResen1

// UDP server
#define _WINSOCK_DEPRECATED_NO_WARNINGS
#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#include "conio.h"

#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")

#define SERVER_PORT 15001
#define BUFFER_SIZE 512


int main()
{
    // Server address
    sockaddr_in serverAddress;

    // Size of sockaddr_in structure
    int sockAddrSize = sizeof(serverAddress);

    // Buffer we will use to receive client message
    char dataBuffer[BUFFER_SIZE];

    // Variable used to store function return value
    int iResult;

    // WSADATA data structure that is to receive details of the Windows Sockets implementation
    WSADATA wsaData;

    // Initialize windows sockets library for this process
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
    {
        printf("WSAStartup failed with error: %d\n", WSAGetLastError());
        return 1;
    }

    // Initialize serverAddress structure used by bind function
    memset((char*)&serverAddress, 0, sockAddrSize);
    serverAddress.sin_family = AF_INET;         // Set server address protocol family
    serverAddress.sin_addr.s_addr = INADDR_ANY; // Use all available addresses of server
    serverAddress.sin_port = htons(SERVER_PORT);

    // Create a socket
    SOCKET serverSocket = socket(AF_INET,      // IPv4 address famly
        SOCK_DGRAM,   // Datagram socket type
        IPPROTO_UDP); // UDP

// Check if socket creation succeeded
    if (serverSocket == INVALID_SOCKET)
    {
        printf("Creating socket failed with error: %d\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }

    // Bind port number and local address to socket
    iResult = bind(serverSocket, (SOCKADDR*)&serverAddress, sockAddrSize);

    if (iResult == SOCKET_ERROR)
    {
        printf("Socket bind failed with error: %d\n", WSAGetLastError());
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }

    printf("Simple UDP server started and waiting client messages.\n");

    int big_letters, small_letters, other_chars;
    char previous[BUFFER_SIZE];


    // Main server loop
    while (1)
    {
        // ClientAddress will be set from recvfrom
        sockaddr_in clientAddress;
        memset(&clientAddress, 0, sockAddrSize);

        // Set whole buffer to zero
        memset(dataBuffer, 0, BUFFER_SIZE);

        // Receive client message
        iResult = recvfrom(serverSocket,
            dataBuffer,
            BUFFER_SIZE,
            0,
            (SOCKADDR*)&clientAddress,
            &sockAddrSize);

        if (iResult == SOCKET_ERROR)
        {
            printf("recvfrom failed with error: %d\n", WSAGetLastError());
            continue;
        }

        // Set end of string
        dataBuffer[iResult] = '\0';

        char ipAddress[16]; // 15 spaces for decimal notation (for example: "192.168.100.200") + '\0'

        // Copy client ip to local char[]
        strcpy_s(ipAddress, sizeof(ipAddress), inet_ntoa(clientAddress.sin_addr));

        // Convert port number from network byte order to host byte order
        unsigned short clientPort = ntohs(clientAddress.sin_port);


        // Check big, small letters and other characters in message
        big_letters = small_letters = other_chars = 0;
        for (int i = 0; i < strlen(dataBuffer); i++)
        {

            // 65 = A, 90 = Z
            if (65 <= dataBuffer[i] && dataBuffer[i] <= 90)
            {
                ++big_letters;
            }
            // 97 = a, 122 = z
            else if (97 <= dataBuffer[i] && dataBuffer[i] <= 122)
            {
                ++small_letters;
            }
            else
                ++other_chars;
        }

        // Log client ip address, port and message text
        printf("Client connected from ip: %s, port: %d, sent: %s.\n", ipAddress, clientPort, dataBuffer);

        //Log number of big, small letters and other characters in message
        printf("Message has %d characters. Big letters: %d, small letters: %d and other characters: %d.\n", iResult, big_letters, small_letters, other_chars);


        // Check if client sent two identical messages consecutively
        //compare current and previous message
        if (!strcmp(previous, dataBuffer))
        {
            printf("Client sent two identical messages consecutively. Server is closing.\n");
            break;
        }
        //store current message for next comparison
        strcpy(previous, dataBuffer);



        // Send message to client
        iResult = sendto(serverSocket,
            dataBuffer,
            strlen(dataBuffer),
            0,
            (SOCKADDR*)&clientAddress,
            sockAddrSize);

        if (iResult == SOCKET_ERROR)
        {
            printf("sendto failed with error: %d\n", WSAGetLastError());
            continue;
        }
    }

    // Close server application
    iResult = closesocket(serverSocket);
    if (iResult == SOCKET_ERROR)
    {
        printf("closesocket failed with error: %ld\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }

    printf("Server successfully shut down.\n");

    WSACleanup();
    return 0;
}