用Java代码实现基于UDP通信的简易一对一聊天室GUI界面。 要求：1.实现客户端与服务器可以相互发送信息。2.实现将文件从客户端上传至服务器或在客户端从服务器下载文件。

以下是基于UDP通信的简易一对一聊天室GUI界面的Java代码实现：

客户端：

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;

public class Client extends JFrame implements ActionListener {
    private JTextField messageField;
    private JTextArea chatArea;
    private JButton sendButton;
    private JButton fileButton;
    private DatagramSocket socket;
    private InetAddress serverAddress;
    private int serverPort;
    private String username;

    public Client(String username, String serverAddress, int serverPort) {
        super("Chat Room - " + username);
        this.username = username;
        this.serverPort = serverPort;
        try {
            this.serverAddress = InetAddress.getByName(serverAddress);
            this.socket = new DatagramSocket();
            this.socket.setSoTimeout(100);
        } catch (UnknownHostException | SocketException e) {
            e.printStackTrace();
        }

        // GUI components
        messageField = new JTextField();
        sendButton = new JButton("Send");
        fileButton = new JButton("File");
        chatArea = new JTextArea();
        chatArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(chatArea);

        JPanel panel = new JPanel(new BorderLayout());
        panel.add(messageField, BorderLayout.CENTER);
        panel.add(sendButton, BorderLayout.EAST);
        panel.add(fileButton, BorderLayout.WEST);

        add(scrollPane, BorderLayout.CENTER);
        add(panel, BorderLayout.SOUTH);

        // Event listeners
        messageField.addActionListener(this);
        sendButton.addActionListener(this);
        fileButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                JFileChooser fileChooser = new JFileChooser();
                int returnValue = fileChooser.showOpenDialog(Client.this);
                if (returnValue == JFileChooser.APPROVE_OPTION) {
                    File file = fileChooser.getSelectedFile();
                    sendFile(file);
                }
            }
        });

        setSize(500, 500);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
    }

    private void sendFile(File file) {
        try {
            byte[] buffer = new byte[1024];
            FileInputStream fis = new FileInputStream(file);
            DatagramPacket packet;
            int bytesRead;
            while ((bytesRead = fis.read(buffer)) != -1) {
                packet = new DatagramPacket(buffer, bytesRead, serverAddress, serverPort);
                socket.send(packet);
            }
            packet = new DatagramPacket(new byte[0], 0, serverAddress, serverPort);
            socket.send(packet);
            fis.close();
            chatArea.append("File sent: " + file.getName() + "\n");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String message = messageField.getText();
        if (!message.equals("")) {
            message = username + ": " + message;
            byte[] buffer = message.getBytes();
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length, serverAddress, serverPort);
            try {
                socket.send(packet);
                messageField.setText("");
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

    public void run() {
        byte[] buffer = new byte[1024];
        while (true) {
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
            try {
                socket.receive(packet);
                String message = new String(packet.getData(), 0, packet.getLength());
                chatArea.append(message + "\n");
            } catch (SocketTimeoutException e) {
                // do nothing
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        String username = JOptionPane.showInputDialog("Enter your name:");
        String serverAddress = JOptionPane.showInputDialog("Enter server address:");
        int serverPort = Integer.parseInt(JOptionPane.showInputDialog("Enter server port:"));
        Client client = new Client(username, serverAddress, serverPort);
        new Thread(client::run).start();
    }
}

服务器：

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

public class Server {
    private DatagramSocket socket;
    private int port;

    public Server(int port) {
        this.port = port;
        try {
            this.socket = new DatagramSocket(port);
            this.socket.setSoTimeout(100);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }

    public void run() {
        byte[] buffer = new byte[1024];
        while (true) {
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
            try {
                socket.receive(packet);
                String message = new String(packet.getData(), 0, packet.getLength());
                if (message.endsWith("\n")) {
                    message = message.substring(0, message.length() - 1);
                }
                if (message.equals("")) {
                    continue;
                }
                if (message.startsWith("FILE:")) {
                    receiveFile(message.substring(5), packet.getAddress(), packet.getPort());
                } else {
                    broadcast(message, packet.getAddress(), packet.getPort());
                }
            } catch (SocketTimeoutException e) {
                // do nothing
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void broadcast(String message, InetAddress address, int port) {
        message = address.getHostAddress() + ":" + port + " " + message;
        byte[] buffer = message.getBytes();
        for (ClientInfo client : clients) {
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length, client.getAddress(), client.getPort());
            try {
                socket.send(packet);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void receiveFile(String filename, InetAddress address, int port) {
        try {
            byte[] buffer = new byte[1024];
            FileOutputStream fos = new FileOutputStream(filename);
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
            while (true) {
                socket.receive(packet);
                if (packet.getLength() == 0) {
                    break;
                }
                fos.write(packet.getData(), 0, packet.getLength());
            }
            fos.close();
            broadcast("File received: " + filename, address, port);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static class ClientInfo {
        private InetAddress address;
        private int port;

        public ClientInfo(InetAddress address, int port) {
            this.address = address;
            this.port = port;
        }

        public InetAddress getAddress() {
            return address;
        }

        public int getPort() {
            return port;
        }
    }

    private List<ClientInfo> clients = new ArrayList<>();

    public void addClient(InetAddress address, int port) {
        clients.add(new ClientInfo(address, port));
    }

    public void removeClient(InetAddress address, int port) {
        clients.removeIf(client -> client.getAddress().equals(address) && client.getPort() == port);
    }

    public static void main(String[] args) {
        int port = Integer.parseInt(JOptionPane.showInputDialog("Enter server port:"));
        Server server = new Server(port);
        new Thread(server::run).start();
    }
}

注意：此代码只是一个演示用例，并不适用于生产环境。在实际应用中，请考虑加密、身份验证、异常处理、性能等方面的问题。