Besoin d'aide sur une application Client/Serveur

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

public class FullDuplex implements AutoCloseable {

    private final BufferedReader in;
    private final BufferedWriter out;

    public FullDuplex(String host, int serverPort, int clientPort, long connectDelay) throws IOException {
        ServerSocket acceptSocket = new ServerSocket(serverPort);
        Socket serverSocket, clientSocket;
        try {
            clientSocket = new Socket(host, clientPort);
            serverSocket = acceptSocket.accept();
        } catch (ConnectException e) {
            serverSocket = acceptSocket.accept();
            clientSocket = new Socket(host, clientPort);
        }
        acceptSocket.close();
        in = new BufferedReader(new InputStreamReader(serverSocket.getInputStream()));
        out = new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
    }

    public String readLine() throws IOException {
        String line = in.readLine();
        System.err.println("Server << " + line);
        return line;
    }

    public void writeLine(String line) throws IOException {
        System.err.println("Client >> " + line);
        out.write(line);
        out.newLine();
        out.flush();
    }

    @Override
    public void close() throws IOException {
        out.close();
        in.close();
    }
}

public static void main(String[] args) throws IOException {
    FullDuplex common = new FullDuplex("localhost", 1026, 1027, 500);
    common.writeLine("What's your name ?");
    String name = common.readLine();
    common.writeLine("Hello " + name + " !");
    common.close();
}

public static void main(String[] args) throws IOException {
    FullDuplex common = new FullDuplex("localhost", 1027, 1026, 500);
    common.readLine();
    common.writeLine(System.getProperty("user.name"));
    common.readLine();
    common.close();
}