자바로 작성하는 기초 채팅 프로그램(클라이언트)

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

public class ChatClient extends JFrame implements ActionListener, Runnable {
	JTextArea output;
	JTextField input;
	JButton send;
	Socket socket;
	BufferedReader br;
	PrintWriter pw;
	Thread t;

	public void init() {
		output = new JTextArea();
		input = new JTextField();
		send = new JButton("보내기");
		JPanel p = new JPanel();

		JScrollPane pane = new JScrollPane(output);
		getContentPane().add("Center", pane);
		output.setEditable(false); // 편집불가능

		p.setLayout(new BorderLayout());
		p.add("Center", input);
		p.add("East", send);

		this.add("South", p);

		// Frame
		setBounds(400, 80, 300, 300);
		setTitle("채팅창");
		setVisible(true);
		// setDefaultCloseOperation(EXIT_ON_CLOSE);

		this.addWindowListener(new WindowAdapter() {// 익명 Inner Class
			public void windowClosing(WindowEvent e) {// Override
				pw.println("quit"); // 서버 보내기
				pw.flush();
				try {
					br.close();
					pw.close();
					socket.close();
				} catch (IOException io) {
					io.printStackTrace();
				}

				System.exit(0);
			}
		});
		// 이벤트
		input.addActionListener(this);
		send.addActionListener(this);

		// 소켓(IO)생성
		String serverIP = JOptionPane.showInputDialog(this, "서버의 IP를 입력하세요",
				"서버IP", JOptionPane.QUESTION_MESSAGE);
		if (serverIP == null || serverIP.equals(""))
			System.exit(0);
		String name = JOptionPane.showInputDialog(this, "대화명을 입력하세요", "대화명",
				JOptionPane.QUESTION_MESSAGE);
		if (name == null || name.equals(""))
			name = "방문자";
		try {
			socket = new Socket(serverIP, 9500);// 서버IP, 포트번호

			// IO
			br = new BufferedReader(new InputStreamReader(
					socket.getInputStream()));
			pw = new PrintWriter(new OutputStreamWriter(
					socket.getOutputStream()));

			// 서버 보내기 - 대화명
			pw.println(name);
			pw.flush();// 버퍼 비우기
			t = new Thread(this);// 쓰레드 생성
			t.start();// 쓰레드 시작->쓰레드 실행(run())
		} catch (UnknownHostException e) {
			System.out.println("소캣생성시 error : " + e.toString());
		} catch (IOException io) {
			System.out.println("소캣생성시 IO error : " + io.toString());
		}
	}// init()

	public void actionPerformed(ActionEvent e) {
		String data = input.getText();
		pw.println(data);
		pw.flush();
		input.setText("");
	}// actionPerformed()

	public void run() {// 쓰레드 구현
		String data = null;
		while (true) {
			try {
				data = br.readLine();
				if (data == null || data.toLowerCase().equals("quit")) {
					br.close();
					pw.close();
					socket.close();
					System.exit(0);
				}// if
			} catch (IOException io) {
				io.printStackTrace();
			}

			output.append(data + "\n");

			int position = output.getText().length();// 위치값 얻기
			output.setCaretPosition(position);
		}// while
	}

	public static void main(String[] args) {
		new ChatClient().init();
	}
}