fix intersections starting independently with no coordination

main/src/main/java/sd/IntersectionProcess.java

@@ -12,17 +12,18 @@ import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
 import sd.config.SimulationConfig;
+import sd.engine.TrafficLightThread;
 import sd.model.Intersection;
 import sd.model.MessageType;
 import sd.model.TrafficLight;
-import sd.model.TrafficLightState;
 import sd.model.Vehicle;
 import sd.protocol.MessageProtocol;
 import sd.protocol.SocketConnection;
 
 /**
  * Main class for an Intersection Process in the distributed traffic simulation.
- * * Each IntersectionProcess runs as an independent Java application (JVM instance)
+ * * Each IntersectionProcess runs as an independent Java application (JVM
+ * instance)
  * representing one of the five intersections (Cr1-Cr5) in the network.
  */
 public class IntersectionProcess {
@@ -41,13 +42,14 @@ public class IntersectionProcess {
 
     private final ExecutorService trafficLightPool;
 
-    private volatile boolean running;   //Quando uma thread escreve um valor volatile, todas as outras
+    private volatile boolean running; // Quando uma thread escreve um valor volatile, todas as outras
-                                        //threads veem a mudança imediatamente.
+                                      // threads veem a mudança imediatamente.
 
     // Traffic Light Coordination
     /**
      * Lock to ensure mutual exclusion between traffic lights.
-     * Only one traffic light can be green at any given time within this intersection.
+     * Only one traffic light can be green at any given time within this
+     * intersection.
      */
     private final Lock trafficCoordinationLock;
 
@@ -91,7 +93,8 @@ public class IntersectionProcess {
     }
 
     /**
-     * Creates traffic lights for this intersection based on its physical connections.
+     * Creates traffic lights for this intersection based on its physical
+     * connections.
      * Each intersection has different number and directions of traffic lights
      * according to the network topology.
      */
@@ -101,19 +104,19 @@ public class IntersectionProcess {
         String[] directions = new String[0];
         switch (intersectionId) {
             case "Cr1":
-                directions = new String[]{"East", "South"};
+                directions = new String[] { "East", "South" };
                 break;
             case "Cr2":
-                directions = new String[]{"West", "East", "South"};
+                directions = new String[] { "West", "East", "South" };
                 break;
             case "Cr3":
-                directions = new String[]{"West", "South"};
+                directions = new String[] { "West", "South" };
                 break;
             case "Cr4":
-                directions = new String[]{"East"};
+                directions = new String[] { "East" };
                 break;
             case "Cr5":
-                directions = new String[]{"East"};
+                directions = new String[] { "East" };
                 break;
         }
 
@@ -125,8 +128,7 @@ public class IntersectionProcess {
                     intersectionId + "-" + direction,
                     direction,
                     greenTime,
-                redTime
+                    redTime);
-            );
 
             intersection.addTrafficLight(light);
             System.out.println("  Created traffic light: " + direction +
@@ -169,6 +171,29 @@ public class IntersectionProcess {
         System.out.println("  Routing configured.");
     }
 
+    /**
+     * Requests permission for a traffic light to turn green.
+     * Blocks until permission is granted (no other light is green).
+     * 
+     * @param direction The direction requesting green light
+     */
+    public void requestGreenLight(String direction) {
+        trafficCoordinationLock.lock();
+        currentGreenDirection = direction;
+    }
+    
+    /**
+     * Releases the green light permission, allowing another light to turn green.
+     * 
+     * @param direction The direction releasing green light
+     */
+    public void releaseGreenLight(String direction) {
+        if (direction.equals(currentGreenDirection)) {
+            currentGreenDirection = null;
+            trafficCoordinationLock.unlock();
+        }
+    }
+    
     /**
      * Starts all traffic light threads.
      */
@@ -176,128 +201,15 @@ public class IntersectionProcess {
         System.out.println("\n[" + intersectionId + "] Starting traffic light threads...");
 
         for (TrafficLight light : intersection.getTrafficLights()) {
-            trafficLightPool.submit(() -> runTrafficLightCycle(light));
+
+            TrafficLightThread lightTask = new TrafficLightThread(light, this, config);
+
+            trafficLightPool.submit(lightTask);
+
             System.out.println("  Started thread for: " + light.getDirection());
         }
     }
 
-    /**
-     * The main loop for a traffic light thread.
-     * Continuously cycles between green and red states.
-     * 
-     * only one traffic light can be green at any given time in this intersection.
-     *
-     * @param light The traffic light to control.
-     */
-    private void runTrafficLightCycle(TrafficLight light) {
-        System.out.println("[" + light.getId() + "] Traffic light thread started.");
-        
-        while (running) {
-            try {
-                // Acquire coordination lock to become green
-                trafficCoordinationLock.lock();
-                try {
-                    // Wait until no other direction is green
-                    while (currentGreenDirection != null && running) {
-                        trafficCoordinationLock.unlock();
-                        Thread.sleep(100); // Brief wait before retrying
-                        trafficCoordinationLock.lock();
-                    }
-                    
-                    if (!running) {
-                        break; // Exit if shutting down
-                    }
-                    
-                    // Mark this direction as the current green light
-                    currentGreenDirection = light.getDirection();
-                    light.changeState(TrafficLightState.GREEN);
-                    System.out.println("[" + light.getId() + "] State: GREEN");
-                    
-                } finally {
-                    trafficCoordinationLock.unlock();
-                }
-                
-                // Process vehicles while green
-                processGreenLight(light);
-                
-                // Wait for green duration
-                Thread.sleep((long) (light.getGreenTime() * 1000));
-                
-                // Release coordination lock (turn red)
-                trafficCoordinationLock.lock();
-                try {
-                    light.changeState(TrafficLightState.RED);
-                    currentGreenDirection = null; // Release exclusive access
-                    System.out.println("[" + light.getId() + "] State: RED (RELEASED ACCESS)");
-                } finally {
-                    trafficCoordinationLock.unlock();
-                }
-                
-                // Wait for red duration
-                Thread.sleep((long) (light.getRedTime() * 1000));
-                
-            } catch (InterruptedException e) {
-                System.out.println("[" + light.getId() + "] Traffic light thread interrupted.");
-                break;
-            }
-        }
-        
-        System.out.println("[" + light.getId() + "] Traffic light thread stopped.");
-    }
-    
-    /**
-     * Processes vehicles when a traffic light is GREEN.
-     * Dequeues vehicles and sends them to their next destination.
-     *
-     * @param light The traffic light that is currently green.
-     */
-    private void processGreenLight(TrafficLight light) {
-        while (light.getState() == TrafficLightState.GREEN && light.getQueueSize() > 0) {
-            Vehicle vehicle = light.removeVehicle();
-            
-            if (vehicle != null) {
-                // Get crossing time based on vehicle type
-                double crossingTime = getCrossingTimeForVehicle(vehicle);
-                
-                // Simulate crossing time
-                try {
-                    Thread.sleep((long) (crossingTime * 1000));
-                } catch (InterruptedException e) {
-                    Thread.currentThread().interrupt();
-                    break;
-                }
-                
-                // Update vehicle statistics
-                vehicle.addCrossingTime(crossingTime);
-                
-                // Update intersection statistics
-                intersection.incrementVehiclesSent();
-                
-                // Send vehicle to next destination
-                sendVehicleToNextDestination(vehicle);
-            }
-        }
-    }
-    
-    /**
-     * Gets the crossing time for a vehicle based on its type.
-     *
-     * @param vehicle The vehicle.
-     * @return The crossing time in seconds.
-     */
-    private double getCrossingTimeForVehicle(Vehicle vehicle) {
-        switch (vehicle.getType()) {
-            case BIKE:
-                return config.getBikeVehicleCrossingTime();
-            case LIGHT:
-                return config.getLightVehicleCrossingTime();
-            case HEAVY:
-                return config.getHeavyVehicleCrossingTime();
-            default:
-                return config.getLightVehicleCrossingTime();
-        }
-    }
-    
     /**
      * Sends a vehicle to its next destination via socket connection.
      *
@@ -314,8 +226,7 @@ public class IntersectionProcess {
             MessageProtocol message = new VehicleTransferMessage(
                     intersectionId,
                     nextDestination,
-                vehicle
+                    vehicle);
-            );
 
             connection.sendMessage(message);
 
@@ -406,17 +317,37 @@ public class IntersectionProcess {
             try {
                 Socket clientSocket = serverSocket.accept();
 
+                System.out.println("[" + intersectionId + "] New connection accepted from " +
+                        clientSocket.getInetAddress().getHostAddress());
+
+                // Check running flag again before handling
+                if (!running) {
+                    clientSocket.close();
+                    break;
+                }
+
+                // **Set timeout before submitting to handler**
+                try {
+                    clientSocket.setSoTimeout(1000);
+                } catch (java.net.SocketException e) {
+                    System.err.println("[" + intersectionId + "] Failed to set timeout: " + e.getMessage());
+                    clientSocket.close();
+                    continue;
+                }
+
                 // Handle each connection in a separate thread
                 connectionHandlerPool.submit(() -> handleIncomingConnection(clientSocket));
 
             } catch (IOException e) {
-                if (running) {
+                // Expected when serverSocket.close() is called during shutdown
+                if (!running) {
+                    break; // Normal shutdown
+                }
                 System.err.println("[" + intersectionId + "] Error accepting connection: " +
                         e.getMessage());
             }
         }
     }
-    }
 
     /**
      * Handles an incoming connection from another process.
@@ -425,6 +356,14 @@ public class IntersectionProcess {
      * @param clientSocket The accepted socket connection.
      */
     private void handleIncomingConnection(Socket clientSocket) {
+        try {
+            clientSocket.setSoTimeout(1000); // 1 second timeout
+
+        } catch (java.net.SocketException e) {
+            System.err.println("[" + intersectionId + "] Failed to set socket timeout: " + e.getMessage());
+            return;
+        }
+
         try (SocketConnection connection = new SocketConnection(clientSocket)) {
 
             System.out.println("[" + intersectionId + "] New connection accepted from " +
@@ -445,9 +384,16 @@ public class IntersectionProcess {
                         intersection.receiveVehicle(vehicle);
                     }
 
+                } catch (java.net.SocketTimeoutException e) {
+                    // Timeout - check running flag and continue
+                    if (!running) {
+                        break;
+                    }
+                    // Continue waiting for next message
                 } catch (ClassNotFoundException e) {
                     System.err.println("[" + intersectionId + "] Unknown message type received: " +
                             e.getMessage());
+                    break; // Invalid message, close connection
                 }
             }
 
@@ -455,6 +401,7 @@ public class IntersectionProcess {
             if (running) {
                 System.err.println("[" + intersectionId + "] Connection error: " + e.getMessage());
             }
+            // Expected during shutdown
         }
     }
 
@@ -463,47 +410,57 @@ public class IntersectionProcess {
      * Shuts down all threads and closes all connections.
      */
     public void shutdown() {
+        // Check if already shutdown
+        if (!running) {
+            return; // Already shutdown, do nothing
+        }
+
         System.out.println("\n[" + intersectionId + "] Shutting down...");
         running = false;
 
-        // Close server socket
+        // 1. Close ServerSocket first
-        try {
         if (serverSocket != null && !serverSocket.isClosed()) {
-                serverSocket.close();
-            }
-        } catch (IOException e) {
-            System.err.println("[" + intersectionId + "] Error closing server socket: " + 
-                             e.getMessage());
-        }
-        
-        // Shutdown thread pools
-        trafficLightPool.shutdown();
-        connectionHandlerPool.shutdown();
-        
             try {
-            if (!trafficLightPool.awaitTermination(5, TimeUnit.SECONDS)) {
+                serverSocket.close();
+            } catch (IOException e) {
+                // Expected
+            }
+        }
+
+        // 2. Shutdown thread pools with force
+        if (trafficLightPool != null && !trafficLightPool.isShutdown()) {
             trafficLightPool.shutdownNow();
         }
-            if (!connectionHandlerPool.awaitTermination(5, TimeUnit.SECONDS)) {
+        if (connectionHandlerPool != null && !connectionHandlerPool.isShutdown()) {
             connectionHandlerPool.shutdownNow();
         }
+
+        // 3. Wait briefly for termination (don't block forever)
+        try {
+            if (trafficLightPool != null) {
+                trafficLightPool.awaitTermination(1, TimeUnit.SECONDS);
+            }
+            if (connectionHandlerPool != null) {
+                connectionHandlerPool.awaitTermination(1, TimeUnit.SECONDS);
+            }
         } catch (InterruptedException e) {
-            trafficLightPool.shutdownNow();
+            Thread.currentThread().interrupt();
-            connectionHandlerPool.shutdownNow();
         }
 
-        // Close all outgoing connections
+        // 4. Close outgoing connections
-        for (Map.Entry<String, SocketConnection> entry : outgoingConnections.entrySet()) {
+        synchronized (outgoingConnections) {
+            for (SocketConnection conn : outgoingConnections.values()) {
                 try {
-                entry.getValue().close();
+                    conn.close();
-            } catch (IOException e) {
+                } catch (Exception e) {
-                System.err.println("[" + intersectionId + "] Error closing connection to " + 
+                    // Ignore
-                                 entry.getKey() + ": " + e.getMessage());
                 }
             }
+            outgoingConnections.clear();
+        }
 
         System.out.println("[" + intersectionId + "] Shutdown complete.");
-        System.out.println("=".repeat(60));
+        System.out.println("============================================================\n");
     }
 
     /**

main/src/main/java/sd/dashboard/DashboardClientHandler.java

@@ -0,0 +1,110 @@
+package sd.dashboard;
+
+import java.io.IOException;
+import java.net.Socket;
+
+import sd.model.MessageType;
+import sd.protocol.MessageProtocol;
+import sd.protocol.SocketConnection;
+
+/**
+ * Processes statistics messages from a single client connection.
+ * Runs in a separate thread per client.
+ */
+public class DashboardClientHandler implements Runnable {
+    
+    private final Socket clientSocket;
+    private final DashboardStatistics statistics;
+    
+    public DashboardClientHandler(Socket clientSocket, DashboardStatistics statistics) {
+        this.clientSocket = clientSocket;
+        this.statistics = statistics;
+    }
+    
+    @Override
+    public void run() {
+        String clientInfo = clientSocket.getInetAddress().getHostAddress() + ":" + clientSocket.getPort();
+        
+        try (SocketConnection connection = new SocketConnection(clientSocket)) {
+            System.out.println("[Handler] Started handling client: " + clientInfo);
+            
+            while (!Thread.currentThread().isInterrupted()) {
+                try {
+                    MessageProtocol message = connection.receiveMessage();
+                    
+                    if (message == null) {
+                        System.out.println("[Handler] Client disconnected: " + clientInfo);
+                        break;
+                    }
+                    
+                    processMessage(message);
+                    
+                } catch (ClassNotFoundException e) {
+                    System.err.println("[Handler] Unknown message class from " + clientInfo + ": " + e.getMessage());
+                } catch (IOException e) {
+                    System.out.println("[Handler] Connection error with " + clientInfo + ": " + e.getMessage());
+                    break;
+                }
+            }
+            
+        } catch (IOException e) {
+            System.err.println("[Handler] Error initializing connection with " + clientInfo + ": " + e.getMessage());
+        } finally {
+            try {
+                if (!clientSocket.isClosed()) {
+                    clientSocket.close();
+                }
+            } catch (IOException e) {
+                System.err.println("[Handler] Error closing socket for " + clientInfo + ": " + e.getMessage());
+            }
+        }
+    }
+    
+    private void processMessage(MessageProtocol message) {
+        if (message.getType() != MessageType.STATS_UPDATE) {
+            System.out.println("[Handler] Ignoring non-statistics message type: " + message.getType());
+            return;
+        }
+        
+        String senderId = message.getSourceNode();
+        Object payload = message.getPayload();
+        
+        System.out.println("[Handler] Received STATS_UPDATE from: " + senderId);
+        
+        if (payload instanceof StatsUpdatePayload stats) {
+            updateStatistics(senderId, stats);
+        } else {
+            System.err.println("[Handler] Unknown payload type: " + 
+                (payload != null ? payload.getClass().getName() : "null"));
+        }
+    }
+    
+    private void updateStatistics(String senderId, StatsUpdatePayload stats) {
+        if (stats.getTotalVehiclesGenerated() >= 0) {
+            statistics.updateVehiclesGenerated(stats.getTotalVehiclesGenerated());
+        }
+        
+        if (stats.getTotalVehiclesCompleted() >= 0) {
+            statistics.updateVehiclesCompleted(stats.getTotalVehiclesCompleted());
+        }
+        
+        if (stats.getTotalSystemTime() >= 0) {
+            statistics.addSystemTime(stats.getTotalSystemTime());
+        }
+        
+        if (stats.getTotalWaitingTime() >= 0) {
+            statistics.addWaitingTime(stats.getTotalWaitingTime());
+        }
+        
+        if (senderId.startsWith("Cr") || senderId.startsWith("E")) {
+            statistics.updateIntersectionStats(
+                senderId,
+                stats.getIntersectionArrivals(),
+                stats.getIntersectionDepartures(),
+                stats.getIntersectionQueueSize()
+            );
+        }
+        
+        System.out.println("[Handler] Successfully updated statistics from: " + senderId);
+    }
+}

main/src/main/java/sd/dashboard/DashboardServer.java

@@ -0,0 +1,148 @@
+package sd.dashboard;
+
+import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import sd.config.SimulationConfig;
+
+/**
+ * Aggregates and displays real-time statistics from all simulation processes.
+ * Uses a thread pool to handle concurrent client connections.
+ */
+public class DashboardServer {
+    
+    private final int port;
+    private final DashboardStatistics statistics;
+    private final ExecutorService clientHandlerPool;
+    private final AtomicBoolean running;
+    private ServerSocket serverSocket;
+    
+    public static void main(String[] args) {
+        System.out.println("=".repeat(60));
+        System.out.println("DASHBOARD SERVER - DISTRIBUTED TRAFFIC SIMULATION");
+        System.out.println("=".repeat(60));
+        
+        try {
+            // Load configuration
+            String configFile = args.length > 0 ? args[0] : "src/main/resources/simulation.properties";
+            System.out.println("Loading configuration from: " + configFile);
+            
+            SimulationConfig config = new SimulationConfig(configFile);
+            DashboardServer server = new DashboardServer(config);
+            
+            // Start the server
+            System.out.println("\n" + "=".repeat(60));
+            server.start();
+            
+            // Keep running until interrupted
+            Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+                System.out.println("\n\nShutdown signal received...");
+                server.stop();
+            }));
+            
+            // Display statistics periodically
+            server.displayLoop();
+            
+        } catch (IOException e) {
+            System.err.println("Failed to start Dashboard Server: " + e.getMessage());
+            System.exit(1);
+        }
+    }
+    
+    public DashboardServer(SimulationConfig config) {
+        this.port = config.getDashboardPort();
+        this.statistics = new DashboardStatistics();
+        this.clientHandlerPool = Executors.newFixedThreadPool(10);
+        this.running = new AtomicBoolean(false);
+    }
+    
+    public void start() throws IOException {
+        if (running.get()) {
+            System.out.println("Dashboard Server is already running.");
+            return;
+        }
+        
+        serverSocket = new ServerSocket(port);
+        running.set(true);
+        
+        System.out.println("Dashboard Server started on port " + port);
+        System.out.println("Waiting for statistics updates from simulation processes...");
+        System.out.println("=".repeat(60));
+        
+        Thread acceptThread = new Thread(this::acceptConnections, "DashboardServer-Accept");
+        acceptThread.setDaemon(false);
+        acceptThread.start();
+    }
+    
+    private void acceptConnections() {
+        while (running.get()) {
+            try {
+                Socket clientSocket = serverSocket.accept();
+                System.out.println("[Connection] New client connected: " + 
+                    clientSocket.getInetAddress().getHostAddress() + ":" + clientSocket.getPort());
+                
+                clientHandlerPool.execute(new DashboardClientHandler(clientSocket, statistics));
+                
+            } catch (IOException e) {
+                if (running.get()) {
+                    System.err.println("[Error] Failed to accept client connection: " + e.getMessage());
+                }
+            }
+        }
+    }
+    
+    @SuppressWarnings("BusyWait")
+    private void displayLoop() {
+        final long DISPLAY_INTERVAL_MS = 5000;
+        
+        while (running.get()) {
+            try {
+                Thread.sleep(DISPLAY_INTERVAL_MS);
+                displayStatistics();
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                break;
+            }
+        }
+    }
+    
+    public void displayStatistics() {
+        System.out.println("\n" + "=".repeat(60));
+        System.out.println("REAL-TIME SIMULATION STATISTICS");
+        System.out.println("=".repeat(60));
+        statistics.display();
+        System.out.println("=".repeat(60));
+    }
+    
+    public void stop() {
+        if (!running.get()) {
+            return;
+        }
+        
+        System.out.println("\nStopping Dashboard Server...");
+        running.set(false);
+        
+        try {
+            if (serverSocket != null && !serverSocket.isClosed()) {
+                serverSocket.close();
+            }
+        } catch (IOException e) {
+            System.err.println("Error closing server socket: " + e.getMessage());
+        }
+        
+        clientHandlerPool.shutdownNow();
+        System.out.println("Dashboard Server stopped.");
+    }
+    
+    public DashboardStatistics getStatistics() {
+        return statistics;
+    }
+    
+    public boolean isRunning() {
+        return running.get();
+    }
+}

main/src/main/java/sd/dashboard/DashboardStatistics.java

@@ -0,0 +1,214 @@
+package sd.dashboard;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+
+import sd.model.VehicleType;
+
+/**
+ * Thread-safe storage for aggregated simulation statistics.
+ * Uses atomic types and concurrent collections for lock-free updates.
+ */
+public class DashboardStatistics {
+    
+    private final AtomicInteger totalVehiclesGenerated;
+    private final AtomicInteger totalVehiclesCompleted;
+    private final AtomicLong totalSystemTime;
+    private final AtomicLong totalWaitingTime;
+    
+    private final Map<String, IntersectionStats> intersectionStats;
+    private final Map<VehicleType, AtomicInteger> vehicleTypeCount;
+    private final Map<VehicleType, AtomicLong> vehicleTypeWaitTime;
+    
+    private volatile long lastUpdateTime;
+    
+    public DashboardStatistics() {
+        this.totalVehiclesGenerated = new AtomicInteger(0);
+        this.totalVehiclesCompleted = new AtomicInteger(0);
+        this.totalSystemTime = new AtomicLong(0);
+        this.totalWaitingTime = new AtomicLong(0);
+        
+        this.intersectionStats = new ConcurrentHashMap<>();
+        this.vehicleTypeCount = new ConcurrentHashMap<>();
+        this.vehicleTypeWaitTime = new ConcurrentHashMap<>();
+        
+        for (VehicleType type : VehicleType.values()) {
+            vehicleTypeCount.put(type, new AtomicInteger(0));
+            vehicleTypeWaitTime.put(type, new AtomicLong(0));
+        }
+        
+        this.lastUpdateTime = System.currentTimeMillis();
+    }
+    
+    public void updateVehiclesGenerated(int count) {
+        totalVehiclesGenerated.set(count);
+        updateTimestamp();
+    }
+    
+    public void incrementVehiclesGenerated() {
+        totalVehiclesGenerated.incrementAndGet();
+        updateTimestamp();
+    }
+    
+    public void updateVehiclesCompleted(int count) {
+        totalVehiclesCompleted.set(count);
+        updateTimestamp();
+    }
+    
+    public void incrementVehiclesCompleted() {
+        totalVehiclesCompleted.incrementAndGet();
+        updateTimestamp();
+    }
+    
+    public void addSystemTime(long timeMs) {
+        totalSystemTime.addAndGet(timeMs);
+        updateTimestamp();
+    }
+    
+    public void addWaitingTime(long timeMs) {
+        totalWaitingTime.addAndGet(timeMs);
+        updateTimestamp();
+    }
+    
+    public void updateVehicleTypeStats(VehicleType type, int count, long waitTimeMs) {
+        vehicleTypeCount.get(type).set(count);
+        vehicleTypeWaitTime.get(type).set(waitTimeMs);
+        updateTimestamp();
+    }
+    
+    public void incrementVehicleType(VehicleType type) {
+        vehicleTypeCount.get(type).incrementAndGet();
+        updateTimestamp();
+    }
+    
+    public void updateIntersectionStats(String intersectionId, int arrivals, 
+                                       int departures, int currentQueueSize) {
+        intersectionStats.compute(intersectionId, (id, stats) -> {
+            if (stats == null) {
+                stats = new IntersectionStats(intersectionId);
+            }
+            stats.updateStats(arrivals, departures, currentQueueSize);
+            return stats;
+        });
+        updateTimestamp();
+    }
+    
+    private void updateTimestamp() {
+        lastUpdateTime = System.currentTimeMillis();
+    }
+    
+    public int getTotalVehiclesGenerated() {
+        return totalVehiclesGenerated.get();
+    }
+    
+    public int getTotalVehiclesCompleted() {
+        return totalVehiclesCompleted.get();
+    }
+    
+    public double getAverageSystemTime() {
+        int completed = totalVehiclesCompleted.get();
+        if (completed == 0) return 0.0;
+        return (double) totalSystemTime.get() / completed;
+    }
+    
+    public double getAverageWaitingTime() {
+        int completed = totalVehiclesCompleted.get();
+        if (completed == 0) return 0.0;
+        return (double) totalWaitingTime.get() / completed;
+    }
+    
+    public int getVehicleTypeCount(VehicleType type) {
+        return vehicleTypeCount.get(type).get();
+    }
+    
+    public double getAverageWaitingTimeByType(VehicleType type) {
+        int count = vehicleTypeCount.get(type).get();
+        if (count == 0) return 0.0;
+        return (double) vehicleTypeWaitTime.get(type).get() / count;
+    }
+    
+    public IntersectionStats getIntersectionStats(String intersectionId) {
+        return intersectionStats.get(intersectionId);
+    }
+    
+    public Map<String, IntersectionStats> getAllIntersectionStats() {
+        return new HashMap<>(intersectionStats);
+    }
+    
+    public long getLastUpdateTime() {
+        return lastUpdateTime;
+    }
+    
+    public void display() {
+        System.out.println("\n--- GLOBAL STATISTICS ---");
+        System.out.printf("Total Vehicles Generated: %d%n", getTotalVehiclesGenerated());
+        System.out.printf("Total Vehicles Completed: %d%n", getTotalVehiclesCompleted());
+        System.out.printf("Vehicles In Transit: %d%n", 
+            getTotalVehiclesGenerated() - getTotalVehiclesCompleted());
+        System.out.printf("Average System Time: %.2f ms%n", getAverageSystemTime());
+        System.out.printf("Average Waiting Time: %.2f ms%n", getAverageWaitingTime());
+        
+        System.out.println("\n--- VEHICLE TYPE STATISTICS ---");
+        for (VehicleType type : VehicleType.values()) {
+            int count = getVehicleTypeCount(type);
+            double avgWait = getAverageWaitingTimeByType(type);
+            System.out.printf("%s: %d vehicles, avg wait: %.2f ms%n", 
+                type, count, avgWait);
+        }
+        
+        System.out.println("\n--- INTERSECTION STATISTICS ---");
+        if (intersectionStats.isEmpty()) {
+            System.out.println("(No data received yet)");
+        } else {
+            for (IntersectionStats stats : intersectionStats.values()) {
+                stats.display();
+            }
+        }
+        
+        System.out.printf("%nLast Update: %tT%n", lastUpdateTime);
+    }
+    
+    public static class IntersectionStats {
+        private final String intersectionId;
+        private final AtomicInteger totalArrivals;
+        private final AtomicInteger totalDepartures;
+        private final AtomicInteger currentQueueSize;
+        
+        public IntersectionStats(String intersectionId) {
+            this.intersectionId = intersectionId;
+            this.totalArrivals = new AtomicInteger(0);
+            this.totalDepartures = new AtomicInteger(0);
+            this.currentQueueSize = new AtomicInteger(0);
+        }
+        
+        public void updateStats(int arrivals, int departures, int queueSize) {
+            this.totalArrivals.set(arrivals);
+            this.totalDepartures.set(departures);
+            this.currentQueueSize.set(queueSize);
+        }
+        
+        public String getIntersectionId() {
+            return intersectionId;
+        }
+        
+        public int getTotalArrivals() {
+            return totalArrivals.get();
+        }
+        
+        public int getTotalDepartures() {
+            return totalDepartures.get();
+        }
+        
+        public int getCurrentQueueSize() {
+            return currentQueueSize.get();
+        }
+        
+        public void display() {
+            System.out.printf("%s: Arrivals=%d, Departures=%d, Queue=%d%n",
+                intersectionId, getTotalArrivals(), getTotalDepartures(), getCurrentQueueSize());
+        }
+    }
+}

main/src/main/java/sd/dashboard/StatsMessage.java

@@ -0,0 +1,48 @@
+package sd.dashboard;
+
+import sd.model.MessageType;
+import sd.protocol.MessageProtocol;
+
+/**
+ * Message wrapper for sending statistics to the dashboard.
+ */
+public class StatsMessage implements MessageProtocol {
+    
+    private static final long serialVersionUID = 1L;
+    
+    private final String sourceNode;
+    private final String destinationNode;
+    private final StatsUpdatePayload payload;
+    
+    public StatsMessage(String sourceNode, StatsUpdatePayload payload) {
+        this.sourceNode = sourceNode;
+        this.destinationNode = "DashboardServer";
+        this.payload = payload;
+    }
+    
+    @Override
+    public MessageType getType() {
+        return MessageType.STATS_UPDATE;
+    }
+    
+    @Override
+    public Object getPayload() {
+        return payload;
+    }
+    
+    @Override
+    public String getSourceNode() {
+        return sourceNode;
+    }
+    
+    @Override
+    public String getDestinationNode() {
+        return destinationNode;
+    }
+    
+    @Override
+    public String toString() {
+        return String.format("StatsMessage[from=%s, to=%s, payload=%s]", 
+            sourceNode, destinationNode, payload);
+    }
+}

main/src/main/java/sd/dashboard/StatsUpdatePayload.java

@@ -0,0 +1,121 @@
+package sd.dashboard;
+
+import java.io.Serializable;
+import java.util.HashMap;
+import java.util.Map;
+
+import sd.model.VehicleType;
+
+/**
+ * Data transfer object for statistics updates to the dashboard.
+ * Use -1 for fields not being updated in this message.
+ */
+public class StatsUpdatePayload implements Serializable {
+    
+    private static final long serialVersionUID = 1L;
+    
+    private int totalVehiclesGenerated = -1;
+    private int totalVehiclesCompleted = -1;
+    private long totalSystemTime = -1;
+    private long totalWaitingTime = -1;
+    
+    private int intersectionArrivals = 0;
+    private int intersectionDepartures = 0;
+    private int intersectionQueueSize = 0;
+    
+    private Map<VehicleType, Integer> vehicleTypeCounts;
+    private Map<VehicleType, Long> vehicleTypeWaitTimes;
+    
+    public StatsUpdatePayload() {
+        this.vehicleTypeCounts = new HashMap<>();
+        this.vehicleTypeWaitTimes = new HashMap<>();
+    }
+    
+    public int getTotalVehiclesGenerated() {
+        return totalVehiclesGenerated;
+    }
+    
+    public int getTotalVehiclesCompleted() {
+        return totalVehiclesCompleted;
+    }
+    
+    public long getTotalSystemTime() {
+        return totalSystemTime;
+    }
+    
+    public long getTotalWaitingTime() {
+        return totalWaitingTime;
+    }
+    
+    public int getIntersectionArrivals() {
+        return intersectionArrivals;
+    }
+    
+    public int getIntersectionDepartures() {
+        return intersectionDepartures;
+    }
+    
+    public int getIntersectionQueueSize() {
+        return intersectionQueueSize;
+    }
+    
+    public Map<VehicleType, Integer> getVehicleTypeCounts() {
+        return vehicleTypeCounts;
+    }
+    
+    public Map<VehicleType, Long> getVehicleTypeWaitTimes() {
+        return vehicleTypeWaitTimes;
+    }
+    
+    public StatsUpdatePayload setTotalVehiclesGenerated(int totalVehiclesGenerated) {
+        this.totalVehiclesGenerated = totalVehiclesGenerated;
+        return this;
+    }
+    
+    public StatsUpdatePayload setTotalVehiclesCompleted(int totalVehiclesCompleted) {
+        this.totalVehiclesCompleted = totalVehiclesCompleted;
+        return this;
+    }
+    
+    public StatsUpdatePayload setTotalSystemTime(long totalSystemTime) {
+        this.totalSystemTime = totalSystemTime;
+        return this;
+    }
+    
+    public StatsUpdatePayload setTotalWaitingTime(long totalWaitingTime) {
+        this.totalWaitingTime = totalWaitingTime;
+        return this;
+    }
+    
+    public StatsUpdatePayload setIntersectionArrivals(int intersectionArrivals) {
+        this.intersectionArrivals = intersectionArrivals;
+        return this;
+    }
+    
+    public StatsUpdatePayload setIntersectionDepartures(int intersectionDepartures) {
+        this.intersectionDepartures = intersectionDepartures;
+        return this;
+    }
+    
+    public StatsUpdatePayload setIntersectionQueueSize(int intersectionQueueSize) {
+        this.intersectionQueueSize = intersectionQueueSize;
+        return this;
+    }
+    
+    public StatsUpdatePayload setVehicleTypeCounts(Map<VehicleType, Integer> vehicleTypeCounts) {
+        this.vehicleTypeCounts = vehicleTypeCounts;
+        return this;
+    }
+    
+    public StatsUpdatePayload setVehicleTypeWaitTimes(Map<VehicleType, Long> vehicleTypeWaitTimes) {
+        this.vehicleTypeWaitTimes = vehicleTypeWaitTimes;
+        return this;
+    }
+    
+    @Override
+    public String toString() {
+        return String.format("StatsUpdatePayload[generated=%d, completed=%d, arrivals=%d, departures=%d, queueSize=%d]",
+            totalVehiclesGenerated, totalVehiclesCompleted, intersectionArrivals, 
+            intersectionDepartures, intersectionQueueSize);
+    }
+}

main/src/main/java/sd/engine/TrafficLightThread.java

@@ -9,150 +9,107 @@ import sd.model.Vehicle;
 /**
  * Implements the control logic for a single TrafficLight
  * as a Runnable task that runs in its own Thread.
- *
  */
 public class TrafficLightThread implements Runnable {
 
-    /**
-     * The TrafficLight object (the *model*) that this thread controls.
-     * Contains the queue and the state.
-     */
     private final TrafficLight light;
-
-    /**
-     * The IntersectionProcess (the Process) that "owns" this thread.
-     * Used to call methods on the process, such as sendVehicleToNextDestination().
-     */
     private final IntersectionProcess process;
-    
-    /**
-     * The simulation configuration, used to get timings (e.g., crossing time).
-     */
     private final SimulationConfig config;
-
-    /**
-     * Volatile flag to control the graceful shutdown mechanism.
-     * When set to 'false', the 'run()' loop terminates.
-     */
     private volatile boolean running;
     
-    /**
+    // Store the thread reference for proper interruption
-     * Constructor for the Traffic Light Thread.
+    private Thread currentThread;
-     *
+
-     * @param light The TrafficLight object (model) to be controlled.
-     * @param process The parent IntersectionProcess (for callbacks).
-     * @param config The simulation configuration (to get timings).
-     */
     public TrafficLightThread(TrafficLight light, IntersectionProcess process, SimulationConfig config) {
         this.light = light;
         this.process = process;
         this.config = config;
-        this.running = false; // Starts as 'stopped'
+        this.running = false;
     }
 
-    /**
-     * The main entry point for the thread.
-     * Implements the GREEN/RED cycle logic extracted from IntersectionProcess.
-     *
-     */
     @Override
     public void run() {
+        this.currentThread = Thread.currentThread();
         this.running = true;
         System.out.println("[" + light.getId() + "] Traffic light thread started.");
 
         try {
-            // Main thread loop, continues while 'running' is true
+            while (running && !Thread.currentThread().isInterrupted()) {
-            // This 'running' flag is controlled by the parent IntersectionProcess
-            while (running) {
                 
+                // Request permission to turn green (blocks until granted)
+                process.requestGreenLight(light.getDirection());
+                
+                try {
                     // --- GREEN Phase ---
-                light.changeState(TrafficLightState.GREEN); //
+                    light.changeState(TrafficLightState.GREEN);
                     System.out.println("[" + light.getId() + "] State: GREEN");
                     
-                // Process vehicles in the queue
                     processGreenLightQueue();
                     
-                // Wait for green duration
+                    if (!running || Thread.currentThread().isInterrupted()) break;
-                Thread.sleep((long) (light.getGreenTime() * 1000)); //
                     
-                if (!running) break; // Check flag after sleep
+                    // Wait for green duration
+                    Thread.sleep((long) (light.getGreenTime() * 1000));
+                    
+                    if (!running || Thread.currentThread().isInterrupted()) break;
 
                     // --- RED Phase ---
-                light.changeState(TrafficLightState.RED); //
+                    light.changeState(TrafficLightState.RED);
                     System.out.println("[" + light.getId() + "] State: RED");
                     
-                // Wait for red duration
+                } finally {
-                Thread.sleep((long) (light.getRedTime() * 1000)); //
+                    // Always release the green light permission
+                    process.releaseGreenLight(light.getDirection());
+                }
                 
+                // Wait for red duration
+                Thread.sleep((long) (light.getRedTime() * 1000));
             }
         } catch (InterruptedException e) {
-            // Apanha a InterruptedException (outra forma de parar a thread)
             System.out.println("[" + light.getId() + "] Traffic light thread interrupted.");
-            this.running = false; // Garante que o loop termina
+            Thread.currentThread().interrupt();
-        }
+        } finally {
-        
+            this.running = false;
             System.out.println("[" + light.getId() + "] Traffic light thread stopped.");
         }
+    }
 
-    /**
-     * Processes vehicles in the queue while the traffic light is GREEN.
-     * Logic extracted from IntersectionProcess.processGreenLight()
-     *
-     */
     private void processGreenLightQueue() throws InterruptedException {
-        //
+        while (running && !Thread.currentThread().isInterrupted() 
-        while (running && light.getState() == TrafficLightState.GREEN && light.getQueueSize() > 0) {
+               && light.getState() == TrafficLightState.GREEN 
+               && light.getQueueSize() > 0) {
             
-            Vehicle vehicle = light.removeVehicle(); //
+            Vehicle vehicle = light.removeVehicle();
             
             if (vehicle != null) {
-                // 1. Get the crossing time (t_sem)
+                double crossingTime = getCrossingTimeForVehicle(vehicle);
-                double crossingTime = getCrossingTimeForVehicle(vehicle); //
                 
-                // 2. Simulate the time the vehicle takes to cross
+                Thread.sleep((long) (crossingTime * 1000));
-                Thread.sleep((long) (crossingTime * 1000)); //
                 
-                // 3. Update vehicle statistics
+                vehicle.addCrossingTime(crossingTime);
-                vehicle.addCrossingTime(crossingTime); //
+                process.getIntersection().incrementVehiclesSent();
-                
+                process.sendVehicleToNextDestination(vehicle);
-                // 4. Update intersection statistics
-               
-                process.getIntersection().incrementVehiclesSent(); //
-                
-                // 5. Call the parent Process to send the vehicle
-               
-                process.sendVehicleToNextDestination(vehicle); //
             }
         }
     }
 
-    /**
-     * Gets the crossing time for a vehicle based on its type.
-     * Logic extracted from IntersectionProcess.getCrossingTimeForVehicle()
-     *
-     *
-     * @param vehicle The vehicle.
-     * @return The crossing time in seconds.
-     */
     private double getCrossingTimeForVehicle(Vehicle vehicle) {
-        switch (vehicle.getType()) { //
+        return switch (vehicle.getType()) {
-            case BIKE:
+            case BIKE -> config.getBikeVehicleCrossingTime();
-                return config.getBikeVehicleCrossingTime(); //
+            case LIGHT -> config.getLightVehicleCrossingTime();
-            case LIGHT:
+            case HEAVY -> config.getHeavyVehicleCrossingTime();
-                return config.getLightVehicleCrossingTime(); //
+            default -> config.getLightVehicleCrossingTime();
-            case HEAVY:
+        };
-                return config.getHeavyVehicleCrossingTime(); //
-            default:
-                return config.getLightVehicleCrossingTime(); //
-        }
     }
 
     /**
-     * Requests the thread to stop gracefully (graceful shutdown).
+     * Requests the thread to stop gracefully.
-     * Sets the 'running' flag to false. The thread will finish
+     * Sets the running flag and interrupts the thread to unblock any sleep() calls.
-     * its current sleep cycle and exit the 'run()' loop.
      */
     public void shutdown() {
         this.running = false;
+        if (currentThread != null && currentThread.isAlive()) {
+            currentThread.interrupt();
+        }
     }
 }

main/src/test/java/IntersectionProcessTest.java

@@ -1,5 +1,5 @@
 import java.io.IOException;
-import java.io.ObjectOutputStream;
+import java.net.InetSocketAddress;
 import java.net.Socket;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -19,6 +19,7 @@ import sd.IntersectionProcess;
 import sd.model.MessageType;
 import sd.model.Vehicle;
 import sd.model.VehicleType;
+import sd.protocol.SocketConnection;
 
 /**
  * Tests for IntersectionProcess - covers initialization, traffic lights,
@@ -96,11 +97,17 @@ public class IntersectionProcessTest {
         Files.writeString(configFile, configContent);
     }
 
-    // cleanup after tests
     @AfterEach
     public void tearDown() {
         if (intersectionProcess != null) {
+            try {
+                // Only shutdown if still running
                 intersectionProcess.shutdown();
+            } catch (Exception e) {
+                System.err.println("Error in tearDown: " + e.getMessage());
+            } finally {
+                intersectionProcess = null;
+            }
         }
     }
 
@@ -187,7 +194,7 @@ public class IntersectionProcessTest {
         intersectionProcess = new IntersectionProcess("Cr1", configFile.toString());
         intersectionProcess.initialize();
 
-        // start server in seperate thread
+        // start server in separate thread
         Thread serverThread = new Thread(() -> {
             try {
                 intersectionProcess.start();
@@ -197,13 +204,22 @@ public class IntersectionProcessTest {
         });
         serverThread.start();
 
-        Thread.sleep(500); // wait for server to start
+        // Wait for server to actually start with retries
-        
+        boolean serverReady = false;
-        // try connecting to check if its running
+        for (int i = 0; i < 20; i++) {
-        try (Socket clientSocket = new Socket("localhost", 18001)) {
+            Thread.sleep(100);
-            assertTrue(clientSocket.isConnected());
+            try (Socket testSocket = new Socket()) {
+                testSocket.connect(new java.net.InetSocketAddress("localhost", 18001), 500);
+                serverReady = true;
+                break;
+            } catch (IOException e) {
+                // Server not ready yet, continue waiting
+            }
         }
 
+        assertTrue(serverReady, "Server should start and bind to port 18001");
+
+        // Shutdown immediately after confirming server is running
         intersectionProcess.shutdown();
         serverThread.join(2000);
     }
@@ -219,11 +235,17 @@ public class IntersectionProcessTest {
         cr2.initialize();
 
         Thread thread1 = new Thread(() -> {
-            try { cr1.start(); } catch (IOException e) { }
+            try {
+                cr1.start();
+            } catch (IOException e) {
+            }
         });
 
         Thread thread2 = new Thread(() -> {
-            try { cr2.start(); } catch (IOException e) { }
+            try {
+                cr2.start();
+            } catch (IOException e) {
+            }
         });
 
         thread1.start();
@@ -256,30 +278,32 @@ public class IntersectionProcessTest {
         Thread serverThread = new Thread(() -> {
             try {
                 intersectionProcess.start();
-            } catch (IOException e) { }
+            } catch (IOException e) {
+            }
         });
         serverThread.start();
 
         Thread.sleep(500);
 
-        // create test vehicle
+        try {
+            // create test vehicle - FIXED: use 4-parameter constructor
             java.util.List<String> route = Arrays.asList("Cr2", "Cr3", "S");
             Vehicle vehicle = new Vehicle("V001", VehicleType.LIGHT, 0.0, route);
 
-        // send vehicle from Cr1 to Cr2
+            // send vehicle from Cr1 to Cr2 - FIXED: use SocketConnection
-        try (Socket socket = new Socket("localhost", 18002)) {
+            try (Socket socket = new Socket("localhost", 18002);
-            ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
+                    SocketConnection conn = new SocketConnection(socket)) {
 
                 TestVehicleMessage message = new TestVehicleMessage("Cr1", "Cr2", vehicle);
-            out.writeObject(message);
+                conn.sendMessage(message);
-            out.flush();
 
-            Thread.sleep(1000); // wait for procesing
+                Thread.sleep(1000); // wait for processing
             }
-        
+        } finally {
             intersectionProcess.shutdown();
             serverThread.join(2000);
         }
+    }
 
     // routing config tests
 
@@ -312,7 +336,8 @@ public class IntersectionProcessTest {
         Thread serverThread = new Thread(() -> {
             try {
                 intersectionProcess.start();
-            } catch (IOException e) { }
+            } catch (IOException e) {
+            }
         });
         serverThread.start();
 
@@ -330,30 +355,35 @@ public class IntersectionProcessTest {
         intersectionProcess = new IntersectionProcess("Cr1", configFile.toString());
         intersectionProcess.initialize();
 
+        // Start server in separate thread
         Thread serverThread = new Thread(() -> {
             try {
                 intersectionProcess.start();
-            } catch (IOException e) { }
+            } catch (IOException e) {
+                // Expected on shutdown
+            }
         });
         serverThread.start();
 
+        // Wait for server to start
         Thread.sleep(500);
 
-        // verify server running
+        // Shutdown
-        try (Socket socket = new Socket("localhost", 18001)) {
-            assertTrue(socket.isConnected());
-        }
-        
         intersectionProcess.shutdown();
         serverThread.join(2000);
 
-        // after shutdown conection should fail
+        // Give shutdown time to complete
-        Thread.sleep(500);
+        Thread.sleep(200);
-        Exception exception = assertThrows(IOException.class, () -> {
+
-            Socket socket = new Socket("localhost", 18001);
+        // Verify we cannot connect (server socket is closed)
-            socket.close();
+        boolean connectionFailed = false;
-        });
+        try (Socket testSocket = new Socket()) {
-        assertNotNull(exception);
+            testSocket.connect(new InetSocketAddress("localhost", 18001), 500);
+        } catch (IOException e) {
+            connectionFailed = true; // Expected - server should be closed
+        }
+
+        assertTrue(connectionFailed, "Server socket should be closed after shutdown");
     }
 
     @Test
@@ -365,7 +395,8 @@ public class IntersectionProcessTest {
         Thread serverThread = new Thread(() -> {
             try {
                 intersectionProcess.start();
-            } catch (IOException e) { }
+            } catch (IOException e) {
+            }
         });
         serverThread.start();
 
@@ -388,20 +419,34 @@ public class IntersectionProcessTest {
     @Test
     @Timeout(15)
     public void testIntegration_TwoIntersectionsVehicleTransfer() throws IOException, InterruptedException {
+        IntersectionProcess cr1 = null;
+        IntersectionProcess cr2 = null;
+        Thread thread1 = null;
+        Thread thread2 = null;
+
+        try {
             // setup 2 intersections
-        IntersectionProcess cr1 = new IntersectionProcess("Cr1", configFile.toString());
+            cr1 = new IntersectionProcess("Cr1", configFile.toString());
-        IntersectionProcess cr2 = new IntersectionProcess("Cr2", configFile.toString());
+            cr2 = new IntersectionProcess("Cr2", configFile.toString());
 
             cr1.initialize();
             cr2.initialize();
 
             // start both
-        Thread thread1 = new Thread(() -> {
+            final IntersectionProcess cr1Final = cr1;
-            try { cr1.start(); } catch (IOException e) { }
+            thread1 = new Thread(() -> {
+                try {
+                    cr1Final.start();
+                } catch (IOException e) {
+                }
             });
 
-        Thread thread2 = new Thread(() -> {
+            final IntersectionProcess cr2Final = cr2;
-            try { cr2.start(); } catch (IOException e) { }
+            thread2 = new Thread(() -> {
+                try {
+                    cr2Final.start();
+                } catch (IOException e) {
+                }
             });
 
             thread1.start();
@@ -409,25 +454,34 @@ public class IntersectionProcessTest {
 
             Thread.sleep(1000); // wait for servers
 
-        // send vehicle to Cr1 that goes to Cr2
+            // send vehicle to Cr1 that goes to Cr2 - FIXED: use 4-parameter constructor
             java.util.List<String> route = Arrays.asList("Cr1", "Cr2", "S");
             Vehicle vehicle = new Vehicle("V001", VehicleType.LIGHT, 0.0, route);
 
-        try (Socket socket = new Socket("localhost", 18001)) {
+            // FIXED: use SocketConnection
-            ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
+            try (Socket socket = new Socket("localhost", 18001);
+                    SocketConnection conn = new SocketConnection(socket)) {
 
                 TestVehicleMessage message = new TestVehicleMessage("Entry", "Cr1", vehicle);
-            out.writeObject(message);
+                conn.sendMessage(message);
-            out.flush();
 
                 Thread.sleep(2000); // time for processing
             }
-        
+        } finally {
+            if (cr1 != null) {
                 cr1.shutdown();
+            }
+            if (cr2 != null) {
                 cr2.shutdown();
+            }
+            if (thread1 != null) {
                 thread1.join(2000);
+            }
+            if (thread2 != null) {
                 thread2.join(2000);
             }
+        }
+    }
 
     @Test
     public void testMain_MissingArguments() {

main/src/test/java/sd/TrafficLightCoordinationTest.java

@@ -1,18 +1,18 @@
 package sd;
 
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
-
-import sd.model.TrafficLight;
-import sd.model.TrafficLightState;
-
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
 
-import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.AfterEach;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import sd.model.TrafficLight;
+import sd.model.TrafficLightState;
 
 /**
  * Test class to verify traffic light coordination within an intersection.
@@ -108,7 +108,7 @@ public class TrafficLightCoordinationTest {
         assertTrue(maxGreenSimultaneously.get() <= 1, 
             "At most ONE light should be GREEN at any time. Found: " + maxGreenSimultaneously.get());
         
-        System.out.println("\n✅ Traffic light coordination working correctly!");
+        System.out.println("\nTraffic light coordination working correctly!");
     }
 
     /**

main/src/test/java/sd/dashboard/DashboardTest.java

@@ -0,0 +1,164 @@
+package sd.dashboard;
+
+import org.junit.jupiter.api.AfterEach;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import sd.config.SimulationConfig;
+import sd.model.VehicleType;
+
+/**
+ * Unit tests for Dashboard Server components.
+ */
+class DashboardTest {
+    
+    private DashboardStatistics statistics;
+    
+    @BeforeEach
+    void setUp() {
+        statistics = new DashboardStatistics();
+    }
+    
+    @AfterEach
+    void tearDown() {
+        statistics = null;
+    }
+    
+    @Test
+    void testInitialStatistics() {
+        assertEquals(0, statistics.getTotalVehiclesGenerated(), 
+            "Initial vehicles generated should be 0");
+        assertEquals(0, statistics.getTotalVehiclesCompleted(), 
+            "Initial vehicles completed should be 0");
+        assertEquals(0.0, statistics.getAverageSystemTime(), 
+            "Initial average system time should be 0.0");
+        assertEquals(0.0, statistics.getAverageWaitingTime(), 
+            "Initial average waiting time should be 0.0");
+    }
+    
+    @Test
+    void testVehicleCounters() {
+        statistics.incrementVehiclesGenerated();
+        assertEquals(1, statistics.getTotalVehiclesGenerated());
+        
+        statistics.updateVehiclesGenerated(10);
+        assertEquals(10, statistics.getTotalVehiclesGenerated());
+        
+        statistics.incrementVehiclesCompleted();
+        assertEquals(1, statistics.getTotalVehiclesCompleted());
+    }
+    
+    @Test
+    void testAverageCalculations() {
+        // Add 3 completed vehicles with known times
+        statistics.updateVehiclesCompleted(3);
+        statistics.addSystemTime(3000); // 3000ms total
+        statistics.addWaitingTime(1500); // 1500ms total
+        
+        assertEquals(1000.0, statistics.getAverageSystemTime(), 0.01,
+            "Average system time should be 1000ms");
+        assertEquals(500.0, statistics.getAverageWaitingTime(), 0.01,
+            "Average waiting time should be 500ms");
+    }
+    
+    @Test
+    void testVehicleTypeStatistics() {
+        statistics.incrementVehicleType(VehicleType.LIGHT);
+        statistics.incrementVehicleType(VehicleType.LIGHT);
+        statistics.incrementVehicleType(VehicleType.HEAVY);
+        
+        assertEquals(2, statistics.getVehicleTypeCount(VehicleType.LIGHT));
+        assertEquals(1, statistics.getVehicleTypeCount(VehicleType.HEAVY));
+        assertEquals(0, statistics.getVehicleTypeCount(VehicleType.BIKE));
+    }
+    
+    @Test
+    void testIntersectionStatistics() {
+        statistics.updateIntersectionStats("Cr1", 10, 8, 2);
+        
+        DashboardStatistics.IntersectionStats stats = 
+            statistics.getIntersectionStats("Cr1");
+        
+        assertNotNull(stats, "Intersection stats should not be null");
+        assertEquals("Cr1", stats.getIntersectionId());
+        assertEquals(10, stats.getTotalArrivals());
+        assertEquals(8, stats.getTotalDepartures());
+        assertEquals(2, stats.getCurrentQueueSize());
+    }
+    
+    @Test
+    void testMultipleIntersections() {
+        statistics.updateIntersectionStats("Cr1", 10, 8, 2);
+        statistics.updateIntersectionStats("Cr2", 15, 12, 3);
+        statistics.updateIntersectionStats("Cr3", 5, 5, 0);
+        
+        assertEquals(3, statistics.getAllIntersectionStats().size(),
+            "Should have 3 intersections");
+    }
+    
+    @Test
+    void testStatsUpdatePayload() {
+        StatsUpdatePayload payload = new StatsUpdatePayload()
+            .setTotalVehiclesGenerated(50)
+            .setTotalVehiclesCompleted(20)
+            .setIntersectionArrivals(30)
+            .setIntersectionDepartures(25)
+            .setIntersectionQueueSize(5);
+        
+        assertEquals(50, payload.getTotalVehiclesGenerated());
+        assertEquals(20, payload.getTotalVehiclesCompleted());
+        assertEquals(30, payload.getIntersectionArrivals());
+        assertEquals(25, payload.getIntersectionDepartures());
+        assertEquals(5, payload.getIntersectionQueueSize());
+    }
+    
+    @Test
+    void testStatsMessage() {
+        StatsUpdatePayload payload = new StatsUpdatePayload()
+            .setIntersectionArrivals(10);
+        
+        StatsMessage message = new StatsMessage("Cr1", payload);
+        
+        assertEquals("Cr1", message.getSourceNode());
+        assertEquals("DashboardServer", message.getDestinationNode());
+        assertEquals(sd.model.MessageType.STATS_UPDATE, message.getType());
+        assertNotNull(message.getPayload());
+    }
+    
+    @Test
+    void testThreadSafety() throws InterruptedException {
+        // Test concurrent updates
+        Thread t1 = new Thread(() -> {
+            for (int i = 0; i < 100; i++) {
+                statistics.incrementVehiclesGenerated();
+            }
+        });
+        
+        Thread t2 = new Thread(() -> {
+            for (int i = 0; i < 100; i++) {
+                statistics.incrementVehiclesGenerated();
+            }
+        });
+        
+        t1.start();
+        t2.start();
+        t1.join();
+        t2.join();
+        
+        assertEquals(200, statistics.getTotalVehiclesGenerated(),
+            "Concurrent increments should total 200");
+    }
+    
+    @Test
+    void testDashboardServerCreation() throws Exception {
+        SimulationConfig config = new SimulationConfig("simulation.properties");
+        DashboardServer server = new DashboardServer(config);
+        
+        assertNotNull(server, "Server should be created successfully");
+        assertNotNull(server.getStatistics(), "Statistics should be initialized");
+        assertFalse(server.isRunning(), "Server should not be running initially");
+    }
+}