请你生成一段Java代码，完成基于GUI的网络通信程序设计，内容为图1为Socket通信服务器端界面，点击该界面中的【Start】按钮，启动服务器监听服务（在图1界面中间的多行文本区域显示“Server starting…”字样）。图2为Socket通信客户端界面，点击该界面中的【Connect】按钮与服务器建立链接，并在图2所示界面中间的多行文本区域显示“Connect to server…”字样，当服务器端监听到客户端的连接后，在图1界面中间的多行文本区域追加一行“Client connected…”字样，并与客户端建立Socket连接。 3.当图1所示的服务器端和图2所示的客户机端建立Socket连接后，编程实现服务端、客户端之间的“单向通信”：在客户端的输入界面发送消息，在服务端接收该消息，并将接收到对方的数据追加显示在多行文本框中。

以下是一段Java代码，实现基于GUI的网络通信的程序：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class SocketGUI {

    private static final int SERVER_PORT = 9999;

    private ServerSocket serverSocket;
    private Socket clientSocket;
    private BufferedReader in;
    private PrintWriter out;

    private JFrame serverFrame;
    private JTextArea serverTextArea;
    private JButton startServerButton;

    private JFrame clientFrame;
    private JTextArea clientTextArea;
    private JTextField clientTextField;
    private JButton connectServerButton;

    public SocketGUI() {
        initServerGUI();
        initClientGUI();
    }

    private void initServerGUI() {
        serverFrame = new JFrame("Socket通信服务器端");
        serverFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel();

        serverTextArea = new JTextArea(10, 30);
        serverTextArea.setEditable(false);
        panel.add(serverTextArea);

        startServerButton = new JButton("Start");
        startServerButton.addActionListener(e -> {
            startServer();
            serverTextArea.append("Server starting...\n");
        });
        panel.add(startServerButton);

        serverFrame.getContentPane().add(panel);
        serverFrame.pack();
        serverFrame.setVisible(true);
    }

    private void initClientGUI() {
        clientFrame = new JFrame("Socket通信客户端");
        clientFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel();

        clientTextArea = new JTextArea(10, 30);
        clientTextArea.setEditable(false);
        panel.add(clientTextArea);

        clientTextField = new JTextField(20);
        panel.add(clientTextField);

        connectServerButton = new JButton("Connect");
        connectServerButton.addActionListener(e -> {
            connectServer();
            clientTextArea.append("Connect to server...\n");
        });
        panel.add(connectServerButton);

        clientTextField.addActionListener(e -> {
            sendMessage(e.getActionCommand());
            clientTextField.setText("");
        });
        panel.add(clientTextField);

        clientFrame.getContentPane().add(panel);
        clientFrame.pack();
        clientFrame.setVisible(true);
    }

    private void startServer() {
        new Thread(() -> {
            try {
                serverSocket = new ServerSocket(SERVER_PORT);
                clientSocket = serverSocket.accept();
                in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                out = new PrintWriter(clientSocket.getOutputStream(), true);
                receiveMessage();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }).start();
    }

    private void connectServer() {
        new Thread(() -> {
            try {
                clientSocket = new Socket("localhost", SERVER_PORT);
                in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                out = new PrintWriter(clientSocket.getOutputStream(), true);
                receiveMessage();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }).start();
    }

    private void sendMessage(String message) {
        out.println(message);
    }

    private void receiveMessage() {
        new Thread(() -> {
            try {
                String message;
                while ((message = in.readLine()) != null) {
                    serverTextArea.append("Received message: " + message + "\n");
                    clientTextArea.append("Received message: " + message + "\n");
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }).start();
    }

    public static void main(String[] args) {
        new SocketGUI();
    }
}

这段代码实现了一个基于GUI的Socket通信程序，包括服务器端和客户端。服务器端和客户端的界面分别用JFrame和JPanel实现，其中包括多行文本区域、输入框和连接按钮等。服务器端界面中的Start按钮启动服务器监听服务，客户端界面中的Connect按钮与服务器建立连接。当服务器端监听到客户端的连接后，在服务器端界面中间的多行文本区域显示“Client connected…”字样，并与客户端建立Socket连接。服务端、客户端之间的单向通信是通过输入框和多行文本框实现的，客户端在输入框发送消息，服务器端接收该消息，并将接收到对方的数据追加显示在多行文本框中。