LV4 - MultipleClientServer

#include <iostream>
#include <WS2tcpip.h>
#include <string>
#include <sstream>

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

#define NMAXCLIENTS 4

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

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

    SOCKET listening = socket(AF_INET, SOCK_STREAM, 0);
    if (listening == INVALID_SOCKET)
    {
        std::cerr << "Error initializing a socket! Bye." << std::endl;
        return -2;
    }

    sockaddr_in hint;
    hint.sin_family = AF_INET;
    hint.sin_port = htons(54000);
    hint.sin_addr.S_un.S_addr = INADDR_ANY;

    bind(listening, (sockaddr*)&hint, sizeof(hint));

    listen(listening, NMAXCLIENTS);

    std::cout << "Server up and running." << std::endl << "Waiting for clients to connect..." << std::endl;

    fd_set master;
    FD_ZERO(&master);

    FD_SET(listening, &master);

    int numOfClients = 0;
    bool running = true;

    while (running)
    {
        fd_set copy = master;
        int socketCount = select(0, &copy, nullptr, nullptr, nullptr);

        for (int i = 0; i < socketCount; i++)
        {
            SOCKET sock = copy.fd_array[i];

            // Inbound connection
            if (sock == listening)
            {
                SOCKET client = accept(listening, nullptr, nullptr);
                FD_SET(client, &master);
                numOfClients++;

                std::string welcomeMsg = "Connected to the server!\r\n";
                send(client, welcomeMsg.c_str(), welcomeMsg.size() + 1, 0);
                std::cout << "Number of clients connected: " << numOfClients << "\r\n";
            }
            // Inbound message
            else
            {
                char buf[4096];
                ZeroMemory(buf, 4096);

                // Receive message
                int bytesIn = recv(sock, buf, 4096, 0);
                std::cout << "Socket #" << sock << ": " << buf << "\r\n";
                if (bytesIn <= 0)
                {
                    closesocket(sock);
                    FD_CLR(sock, &master);
                    numOfClients--;
                    std::cout << "Number of clients connected: " << numOfClients << "\r\n";
                }
                else
                {
                    if (buf[0] == 'N')
                    {
                        std::string name = std::string(buf, bytesIn);
                        std::ostringstream clientNumMessageStream;
                        clientNumMessageStream << "B" << numOfClients << "\r\n";
                        std::string clientNumMessage = clientNumMessageStream.str();
                        send(sock, clientNumMessage.c_str(), clientNumMessage.size() + 1, 0);
                    }

                    // Send message to other clients
                    if (numOfClients == NMAXCLIENTS) {
                        for (int i = 0; i < master.fd_count; i++)
                        {
                            SOCKET outSock = master.fd_array[i];
                            if (outSock != listening)
                            {
                                std::string strOut = "P";
                                send(outSock, strOut.c_str(), strOut.size() + 1, 0);
                            }
                        }
                    }

                    else if (numOfClients > NMAXCLIENTS) {
                        std::cout << "Max client count exceeded, shutting down the server..." << std::endl;
                        running = false;
                        break;
                    }
                }
            }
        }
    }

    FD_CLR(listening, &master);
    closesocket(listening);

    std::string msg = "Server is shutting down...\r\n";

    while (master.fd_count > 0)
    {
        SOCKET sock = master.fd_array[0];
        send(sock, msg.c_str(), msg.size() + 1, 0);
        FD_CLR(sock, &master);
        closesocket(sock);
    }

    WSACleanup();

    system("pause");
    return 0;
}