Client+1

#include <iostream>
#include <string>
#include <ws2tcpip.h>

using namespace std;

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

int main()
{
    setlocale(0, "");
    system("title CLIENT SIDE");

    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);

    addrinfo hints{};
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    addrinfo* result = NULL;
    getaddrinfo("localhost", "27015", &hints, &result);

    SOCKET ConnectSocket = socket(result->ai_family,result->ai_socktype,result->ai_protocol);

    connect(ConnectSocket,result->ai_addr,(int)result->ai_addrlen);

    freeaddrinfo(result);

    cout << "Connected to server!\n";

    while (true)
    {
        string input;

        cout << "\nEnter integer (type exit to quit): ";
        getline(cin, input);

        send(ConnectSocket, input.c_str(),input.size(), 0 );

        if (input == "exit")
            break;

        char buffer[512]{};

        int bytes = recv( ConnectSocket, buffer,511,0);

        if (bytes > 0)
        {
            buffer[bytes] = '\0';
            cout << "Server response: " << buffer << endl;
        }
        else
            break;
    }

    shutdown(ConnectSocket, SD_SEND);
    closesocket(ConnectSocket);
    WSACleanup();

    cout << "Client stopped.\n";

    return 0;
}

server+1

#include <iostream>
#include <string>
#include <ws2tcpip.h>

using namespace std;

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

int main()
{
    setlocale(0, "");
    system("title SERVER SIDE");

    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);

    addrinfo hints{};
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_flags = AI_PASSIVE;

    addrinfo* result = NULL;
    getaddrinfo(NULL, "27015", &hints, &result);

    SOCKET ListenSocket = socket(result->ai_family, result->ai_socktype,result->ai_protocol);

    bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);
    freeaddrinfo(result);

    listen(ListenSocket, SOMAXCONN);

    cout << "Waiting for client...\n";

    SOCKET ClientSocket = accept(ListenSocket, NULL, NULL);
    closesocket(ListenSocket);

    cout << "Client connected!\n";

    while (true)
    {
        char buffer[512]{};

        int bytes = recv(ClientSocket, buffer, 511, 0);

        if (bytes > 0)
        {
            buffer[bytes] = '\0';

            string text = buffer;

            if (text == "exit")
                break;

            try
            {
                int number = stoi(text);
                int resultNumber = number + 1;

                string response = to_string(resultNumber);

                send(ClientSocket,response.c_str(),response.size(),0);
            }
            catch (...)
            {
                string error = "Invalid number";
                send(ClientSocket,error.c_str(), error.size(),0);
            }
        }
        else
            break;
    }

    shutdown(ClientSocket, SD_SEND);
    closesocket(ClientSocket);
    WSACleanup();

    cout << "Server stopped.\n";

    return 0;
}