Add connection retry logic

main/src/main/java/sd/protocol/SocketConnection.java

@@ -4,18 +4,15 @@ 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.
- * * It encapsulates all stream logic (ObjectInputStream/ObjectOutputStream)
+ * Includes connection retry logic for robustness.
- * so the rest of your code can simply "send" and "receive" objects
- * that implement your MessageProtocol.
- * * This is necessary to meet the requirement for inter-process communication
- * (Intersections).
- * * This class implements Closeable, so you can (and should) use it 
- * with a 'try-with-resources' block to ensure the socket is always closed.
  */
 public class SocketConnection implements Closeable {
 
@@ -23,27 +20,91 @@ public class SocketConnection implements Closeable {
     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.
+     * @throws IOException If connection fails after all retries.
-     * @throws UnknownHostException If the host is not found.
+     * @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 {
+    public SocketConnection(String host, int port) throws IOException, UnknownHostException, InterruptedException {
-        this.socket = new Socket(host, port);
+        Socket tempSocket = null;
+        IOException lastException = null;
 
-        // IMPORTANT: The order is crucial to prevent deadlocks when creating streams.
+        System.out.printf("[SocketConnection] Attempting to connect to %s:%d...%n", host, port);
-        // The OutputStream (output stream) must be created first.
+
+        // --- 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.
@@ -51,18 +112,23 @@ public class SocketConnection implements Closeable {
     public SocketConnection(Socket acceptedSocket) throws IOException {
         this.socket = acceptedSocket;
 
-        // IMPORTANT: The order is crucial. OutputStream (output stream) must be created first.
+        // 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.
+     * @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.
@@ -74,10 +140,13 @@ public class SocketConnection implements Closeable {
      * This call is "blocked" until an object is received.
      *
      * @return The "envelope" (MessageProtocol) that was received.
-     * @throws IOException If the connection is lost or the stream is corrupted.
+     * @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();
         }
@@ -89,6 +158,9 @@ public class SocketConnection implements Closeable {
      */
     @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 */ }
@@ -103,7 +175,7 @@ public class SocketConnection implements Closeable {
     }
 
     /**
-     * @return true if the socket is still connected.
+     * @return true if the socket is still connected and not closed.
      */
     public boolean isConnected() {
         return socket != null && socket.isConnected() && !socket.isClosed();