iovi-network/server/ServerSocketThread.cpp

#include "ServerSocketThread.h"
#include <iostream>
#include <stdexcept>

// THE CONSTRUCTOR
ServerSocketThread::ServerSocketThread(const int p) : serverSocket(INVALID_SOCKET), port(p) {}

// THE DESTRUCTOR
// If the object is destroyed, we MUST ensure the background thread is stopped first!
ServerSocketThread::~ServerSocketThread() {
    stop();
}

// THE START (Spawning the Worker)
void ServerSocketThread::start() {
    if (running.load()) {
        std::cerr << "⚠️ Server is already running!\n";
        return;
    }

    // =========================================================================
    // STEP 1: CREATE, BIND, LISTEN (Same as before, but in the main thread)
    // =========================================================================
    serverSocket = socket(AF_INET, SOCK_STREAM, 0);
    if (serverSocket == INVALID_SOCKET) {
        throw std::runtime_error("Failed to create socket!");
    }

    constexpr int opt = 1;
    setsockopt(serverSocket, SOL_SOCKET, SO_REUSEADDR, (const char*)&opt, sizeof(opt));

    sockaddr_in serverAddr{};
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = INADDR_ANY;
    serverAddr.sin_port = htons(port);

    if (bind(serverSocket, reinterpret_cast<sockaddr*>(&serverAddr), sizeof(serverAddr)) == SOCKET_ERROR) {
        throw std::runtime_error("Failed to bind to port " + std::to_string(port) + "!");
    }

    if (listen(serverSocket, SOMAXCONN) == SOCKET_ERROR) {
        throw std::runtime_error("Failed to listen!");
    }

    // =========================================================================
    // STEP 2: RAISE THE "GO" FLAG AND SPAWN THE THREAD
    // =========================================================================
    running.store(true);

    // We pass 'this' so the background thread can access the serverLoop method
    serverThread = std::thread(&ServerSocketThread::serverLoop, this);

    std::cout << "🟢 Server thread started and listening on port " << port << "...\n";
}

// THE STOP METHOD (The Interrupt Command)
void ServerSocketThread::stop() {
    if (!running.load()) {
        std::cerr << "⚠️ Server is already stopped!\n";
        return;
    }

    std::cout << "\n🛑 Interrupt received. Shutting down server...\n";

    // Lower the "Go" flag. The background loop will see this on its next check.
    running.store(false);

    // FORCE WAKEUP TRICK: Closing the socket from THIS thread will immediately
    // cause the 'select' or 'accept' call in the OTHER thread to fail and return.
    // This guarantees we don't have to wait for the 1-second timeout to finish!
    if (serverSocket != INVALID_SOCKET) {
        CLOSE_SOCKET(serverSocket);
        serverSocket = INVALID_SOCKET;
    }

    // Wait for the background thread to finish its cleanup and join us.
    if (serverThread.joinable()) {
        serverThread.join();
    }

    std::cout << "✅ Server thread stopped cleanly.\n";
}

// THE SERVER LOOP (The Background Algorithm)
void ServerSocketThread::serverLoop() const {
    std::cout << "🟢 Server loop is now running in the background.\n";

    // We loop AS LONG AS the stop sign is NOT raised.
    while (running.load()) {

        // =====================================================================
        // STEP 3: THE ALARM CLOCK (select with timeout)
        // =====================================================================
        // Instead of blocking forever on accept(), we ask the OS:
        // "Is there a client trying to connect? I'll wait up to 1 second."
        fd_set readfds;
        FD_ZERO(&readfds);
        FD_SET(serverSocket, &readfds);

        timeval tv{};
        tv.tv_sec = 1;  // 1 second timeout
        tv.tv_usec = 0;

        // select() returns:
        // > 0 : The socket is ready to be accepted
        //   0 : Timeout (1 second passed, no clients)
        // < 0 : Error (or the socket was closed by our stop() method)
#ifdef _WIN32
        const int activity = select(0, &readfds, nullptr, nullptr, &tv); // Windows ignores the first param
#else
        // POSIX needs max_fd + 1
        const int activity = select(static_cast<int>(serverSocket + 1), &readfds, nullptr, nullptr, &tv);
#endif

        // CRITICAL CHECK: Did someone call stop() while we were sleeping?
        if (!running.load()) {
            break; // Exit the loop immediately
        }

        if (activity > 0 && FD_ISSET(serverSocket, &readfds)) {
            // =================================================================
            // STEP 4: ACCEPT (A client is here)
            // =================================================================
            sockaddr_in clientAddr{};
            socklen_t clientLen = sizeof(clientAddr);

            if (SOCKET_TYPE clientSocket = accept(serverSocket, reinterpret_cast<sockaddr*>(&clientAddr), &clientLen);
                clientSocket != INVALID_SOCKET) {
                std::cout << "📞 New client connected! Spawning handler thread...\n";

                // Spawn a detached thread to handle this specific client
                std::thread([clientSocket]() {
                    handleClient(clientSocket);
                }).detach();
            }
        }
        else if (activity < 0) {
            // This usually happens when stop() closes the socket, forcing select to return an error.
            // We just break the loop to shut down gracefully.
            std::cout << "Usually happens when stop() closes the socket\n";
            break;
        }
        // If activity == 0, it's just a timeout. The while loop repeats,
        // checks isRunning again, and sets the alarm clock for another second.
    }
}

// 6. THE HELPER METHOD (Unchanged, perfectly safe echo logic)
void ServerSocketThread::handleClient(SOCKET_TYPE clientSocket) {
    char buffer[1025];

    while (true) {
        auto bytesReceived = recv(clientSocket, buffer, sizeof(buffer) - 1, 0);

        if (bytesReceived <= 0) {
            std::cout << "📴 Client disconnected.\n";
            break;
        }

        const auto len = static_cast<size_t>(bytesReceived);
        buffer[len] = '\0';
        std::cout << "📩 Received: " << buffer;

        send(clientSocket, buffer, static_cast<int>(len), 0);
    }
    CLOSE_SOCKET(clientSocket);
}