chat server & client

SERVER

public class Server {

	private static final int PORT = 9001;

	private static HashSet<String> names = new HashSet<String>();
	private static HashSet<PrintWriter> writers = new HashSet<PrintWriter>();

	public static void main(String[] args) throws Exception {
		System.out.println("The chat server is running.");
		ServerSocket listener = new ServerSocket(PORT);

		try {
			while (true) {
				new Handler(listener.accept()).start();
			}
		} finally {
			listener.close();
		}

	}

	private static class Handler extends Thread {
		private String name;
		private Socket socket;
		private BufferedReader in;
		private PrintWriter out;

		public Handler(Socket socket) {
			this.socket = socket;
		}

		public void run() {
			try {
				in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
				out = new PrintWriter(socket.getOutputStream(), true);
				DataInputStream din = new DataInputStream(socket.getInputStream());

				// Note that
				// checking for the existence of a name and adding the name
				// must be done while locking the set of names.
				while (true) {
					out.println("SUBMITNAME");
					name = in.readLine();
					if (name == null) {
						return;
					}
					synchronized (names) {
						if (!names.contains(name)) {
							names.add(name);
							break;
						}
					}
				}

				// socket's print writer to the set of all writers so
				// this client can receive broadcast messages.
				out.println("NAMEACCEPTED");
				writers.add(out);
				System.out.println(din.readUTF());

				while(true) {
					String input = in.readLine();
					if (input == null) {
						return;
					}
					for (PrintWriter writer : writers) {
						writer.println("MESSAGE " + name + ": " + input);
					}
				}
			} catch (IOException e) {
				System.out.println(e);
			} finally {
				if (name != null) {
					names.remove(name);
				}
				if (out != null) {
					writers.remove(out);
				}
				try {
					socket.close();
				} catch (IOException e) {
				}
			}
		}
	}
}

---

 

CLIENT

public class Client {

	BufferedReader in;
	PrintWriter out;
	JFrame frame = new JFrame("Chatter");
	JTextField textField = new JTextField(40);
	JTextArea messageArea = new JTextArea(8, 40);

	public Client() {
		// Layout GUI
		textField.setEditable(false);
		messageArea.setEditable(false);
		frame.getContentPane().add(textField, "North");
		frame.getContentPane().add(new JScrollPane(messageArea), "Center");
		frame.pack();

		// add listeners
		textField.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent e) {
				out.println(textField.getText());
				textField.setText("");
			}
		});
	}

	private String getServerAddress() {
		return JOptionPane.showInputDialog(
				frame,
				"Enter IP Address of the Server:",
				"Welcome to the Chatter",
				JOptionPane.QUESTION_MESSAGE);
	}

	private String getName() {
		return JOptionPane.showInputDialog(
				frame,
				"Choose a screen name:",
				"Screen name selection",
				JOptionPane.PLAIN_MESSAGE);
	}

	private void run() throws UnknownHostException, IOException {
		String serverAddress = getServerAddress();
		Socket socket = new Socket(serverAddress, 9001);
		in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
		out = new PrintWriter(socket.getOutputStream(), true);
		DataOutputStream dos = new DataOutputStream(socket.getOutputStream());

		while (true) {
			String line = in.readLine();
			if (line.startsWith("SUBMITNAME")) {
				out.println(getName());
			} else if (line.startsWith("NAMEACCEPTED")) {
				textField.setEditable(true);
				dos.writeUTF("파일이름");
			} else if (line.startsWith("MESSAGE")) {
				messageArea.append(line.substring(8) + "\n");
			}
		}
	}

	public static void main(String[] args) throws UnknownHostException, IOException {
		Client client = new Client();
		client.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		client.frame.setVisible(true);
		client.run();
	}
}