diff --git a/main/src/main/java/sd/protocol/MessageProtocol.java b/main/src/main/java/sd/protocol/MessageProtocol.java new file mode 100644 index 0000000..47975be --- /dev/null +++ b/main/src/main/java/sd/protocol/MessageProtocol.java @@ -0,0 +1,41 @@ +package sd.protocol; + +import java.io.Serializable; +import sd.model.MessageType; // Assuming MessageType is in sd.model or sd.protocol + +/** + * Interface defining the contract for all messages exchanged in the simulator. + * Ensures that any message can be identified and routed. + * * This interface extends Serializable to allow objects that implement it + * to be sent over Sockets (ObjectOutputStream). + * + */ +public interface MessageProtocol extends Serializable { + + /** + * Returns the type of the message, indicating its purpose. + * @return The MessageType (e.g., VEHICLE_TRANSFER, STATS_UPDATE). + */ + MessageType getType(); + + /** + * Returns the data object (payload) that this message carries. + * The type of object will depend on the MessageType. + * * - If getType() == VEHICLE_TRANSFER, the payload will be a {@link sd.model.Vehicle} object. + * - If getType() == STATS_UPDATE, the payload will be a statistics object. + * * @return The data object (payload), which must also be Serializable. + */ + Object getPayload(); + + /** + * Returns the ID of the node (Process) that sent this message. + * @return String (e.g., "Cr1", "Cr5", "S"). + */ + String getSourceNode(); + + /** + * Returns the ID of the destination node (Process) for this message. + * @return String (e.g., "Cr2", "DashboardServer"). + */ + String getDestinationNode(); +} \ No newline at end of file diff --git a/main/src/main/java/sd/protocol/SocketConnection.java b/main/src/main/java/sd/protocol/SocketConnection.java new file mode 100644 index 0000000..f6392a4 --- /dev/null +++ b/main/src/main/java/sd/protocol/SocketConnection.java @@ -0,0 +1,183 @@ +package sd.protocol; + +import java.io.Closeable; +import java.io.IOException; +import java.io.ObjectInputStream; +import java.io.ObjectOutputStream; +import java.net.ConnectException; +import java.net.Socket; +import java.net.SocketTimeoutException; +import java.net.UnknownHostException; +import java.util.concurrent.TimeUnit; + +/** + * Wrapper class that simplifies communication via Sockets. + * Includes connection retry logic for robustness. + */ +public class SocketConnection implements Closeable { + + private final Socket socket; + private final ObjectOutputStream outputStream; + private final ObjectInputStream inputStream; + + // --- Configuration for Retry Logic --- + /** Maximum number of connection attempts. */ + private static final int MAX_RETRIES = 5; + /** Delay between retry attempts in milliseconds. */ + private static final long RETRY_DELAY_MS = 1000; + + /** + * Constructor for the "Client" (who initiates the connection). + * Tries to connect to a process that is already listening (Server). + * Includes retry logic in case of initial connection failure. + * + * @param host The host address (e.g., "localhost" from your simulation.properties) + * @param port The port (e.g., 8001 from your simulation.properties) + * @throws IOException If connection fails after all retries. + * @throws UnknownHostException If the host is not found (this error usually doesn't need retry). + * @throws InterruptedException If the thread is interrupted while waiting between retries. + */ + public SocketConnection(String host, int port) throws IOException, UnknownHostException, InterruptedException { + Socket tempSocket = null; + IOException lastException = null; + + System.out.printf("[SocketConnection] Attempting to connect to %s:%d...%n", host, port); + + // --- Retry Loop --- + for (int attempt = 1; attempt <= MAX_RETRIES; attempt++) { + try { + // Try to establish the connection + tempSocket = new Socket(host, port); + + // If successful, break out of the retry loop + System.out.printf("[SocketConnection] Connected successfully on attempt %d.%n", attempt); + lastException = null; // Clear last error on success + break; + + } catch (ConnectException | SocketTimeoutException e) { + // These are common errors indicating the server might not be ready. + lastException = e; + System.out.printf("[SocketConnection] Attempt %d/%d failed: %s. Retrying in %d ms...%n", + attempt, MAX_RETRIES, e.getMessage(), RETRY_DELAY_MS); + + if (attempt < MAX_RETRIES) { + // Wait before the next attempt + TimeUnit.MILLISECONDS.sleep(RETRY_DELAY_MS); + } + } catch (IOException e) { + // Other IOExceptions might be more permanent, but we retry anyway. + lastException = e; + System.out.printf("[SocketConnection] Attempt %d/%d failed with IOException: %s. Retrying in %d ms...%n", + attempt, MAX_RETRIES, e.getMessage(), RETRY_DELAY_MS); + if (attempt < MAX_RETRIES) { + TimeUnit.MILLISECONDS.sleep(RETRY_DELAY_MS); + } + } + } // --- End of Retry Loop --- + + // If after all retries tempSocket is still null, it means connection failed permanently. + if (tempSocket == null) { + System.err.printf("[SocketConnection] Failed to connect to %s:%d after %d attempts.%n", host, port, MAX_RETRIES); + if (lastException != null) { + throw lastException; // Throw the last exception encountered + } else { + // Should not happen if loop ran, but as a fallback + throw new IOException("Failed to connect after " + MAX_RETRIES + " attempts, reason unknown."); + } + } + + // If connection was successful, assign to final variable and create streams + this.socket = tempSocket; + try { + // IMPORTANT: The order is crucial. OutputStream first. + this.outputStream = new ObjectOutputStream(socket.getOutputStream()); + this.inputStream = new ObjectInputStream(socket.getInputStream()); + } catch (IOException e) { + // If stream creation fails even after successful socket connection, clean up. + System.err.println("[SocketConnection] Failed to create streams after connection: " + e.getMessage()); + try { socket.close(); } catch (IOException closeEx) { /* ignore */ } + throw e; // Re-throw the stream creation exception + } + } + + + /** + * Constructor for the "Server" (who accepts the connection). + * Receives a Socket that has already been accepted by a ServerSocket. + * No retry logic needed here as the connection is already established. + * + * @param acceptedSocket The Socket returned by serverSocket.accept(). + * @throws IOException If stream creation fails. + */ + public SocketConnection(Socket acceptedSocket) throws IOException { + this.socket = acceptedSocket; + + // IMPORTANT: The order is crucial. OutputStream first. + this.outputStream = new ObjectOutputStream(socket.getOutputStream()); + this.inputStream = new ObjectInputStream(socket.getInputStream()); + System.out.printf("[SocketConnection] Connection accepted from %s:%d.%n", + acceptedSocket.getInetAddress().getHostAddress(), acceptedSocket.getPort()); + } + + /** + * Sends (serializes) a MessageProtocol object over the socket. + * + * @param message The "envelope" (which contains the Vehicle) to be sent. + * @throws IOException If writing to the stream fails or socket is not connected. + */ + public void sendMessage(MessageProtocol message) throws IOException { + if (!isConnected()) { + throw new IOException("Socket is not connected."); + } + synchronized (outputStream) { + outputStream.writeObject(message); + outputStream.flush(); // Ensures the message is sent immediately. + } + } + + /** + * Tries to read (deserialize) a MessageProtocol object from the socket. + * This call is "blocked" until an object is received. + * + * @return The "envelope" (MessageProtocol) that was received. + * @throws IOException If the connection is lost, the stream is corrupted, or socket is not connected. + * @throws ClassNotFoundException If the received object is unknown. + */ + public MessageProtocol receiveMessage() throws IOException, ClassNotFoundException { + if (!isConnected()) { + throw new IOException("Socket is not connected."); + } + synchronized (inputStream) { + return (MessageProtocol) inputStream.readObject(); + } + } + + /** + * Closes the socket and all streams (Input and Output). + * It is called automatically if you use 'try-with-resources'. + */ + @Override + public void close() throws IOException { + System.out.printf("[SocketConnection] Closing connection to %s:%d.%n", + socket != null ? socket.getInetAddress().getHostAddress() : "N/A", + socket != null ? socket.getPort() : -1); + try { + if (inputStream != null) inputStream.close(); + } catch (IOException e) { /* ignore */ } + + try { + if (outputStream != null) outputStream.close(); + } catch (IOException e) { /* ignore */ } + + if (socket != null && !socket.isClosed()) { + socket.close(); + } + } + + /** + * @return true if the socket is still connected and not closed. + */ + public boolean isConnected() { + return socket != null && socket.isConnected() && !socket.isClosed(); + } +} \ No newline at end of file