ClientHandler.java

import java.io.*;
import java.net.Socket;

public class ClientHandler extends Thread {

    private final Socket          socket;
    private final SequenceBuffer  sequenceBuffer; // Phase 3 — in-order delivery
    private final String          clientName;

    public ClientHandler(Socket socket, SequenceBuffer sequenceBuffer, String clientName) {
        super("ClientHandler-" + clientName);
        this.socket          = socket;
        this.sequenceBuffer  = sequenceBuffer;
        this.clientName      = clientName;
    }

    @Override
    public void run() {
        System.out.printf("[Server] %s connected from %s%n",
            clientName, socket.getInetAddress());

        try (ObjectInputStream in = new ObjectInputStream(socket.getInputStream())) {
            while (true) {
                Object obj = in.readObject();
                if (!(obj instanceof Order)) break;

                Order order = (Order) obj;
                if (order.getSequenceId() == -1) {
                    System.out.printf("[Server] %s sent disconnect signal.%n", clientName);
                    break;
                }

                sequenceBuffer.add(order); // buffered, in-order release to engine
                System.out.printf("[Server] Received from %s: %s%n", clientName, order);
            }
        } catch (EOFException e) {
            System.out.printf("[Server] %s closed connection.%n", clientName);
        } catch (IOException | ClassNotFoundException | InterruptedException e) {
            System.out.printf("[Server] %s error: %s%n", clientName, e.getMessage());
        }
    }
}