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Java Socket 實作多執行緒聊天室完整範例

編輯：Java 相關知識

前言

近期深入研究 Java Socket 網路通訊基礎，動手實作一個支援多用戶同時線上聊天的即時通訊室。這裡將完整的專案架構、核心程式碼與執行步驟分享給有興趣的開發者參考，希望能幫助大家快速掌握 Socket 程式設計的精髓。

專案目錄結構

專案採用標準 Maven 結構，主要分為客戶端與伺服器端兩大模組：

專案目錄結構圖

核心程式碼解析

1. 聊天客戶端 - ChatClient

客戶端採用 AWT 圖形介面，包含訊息顯示區、輸入框，並使用獨立執行緒持續監聽伺服器推送的訊息。

package com.panda.chat;

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

@SuppressWarnings("serial")
public class ChatClient extends Frame {
    private TextArea ta = new TextArea();
    private TextField tf = new TextField();
    private DataOutputStream dos = null;
    private DataInputStream dis = null;
    private Socket socket = null;
    private boolean bConnected = false;
    private Thread thread = null;

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

    public void frameClient() {
        setSize(400, 400);
        setLocation(400, 300);
        add(ta, BorderLayout.NORTH);
        add(tf, BorderLayout.SOUTH);
        pack();

        tf.addActionListener(new TfListener());
        this.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                disconnected();
                System.exit(0);
            }
        });

        this.connect();
        setVisible(true);
    }

    private void connect() {
        try {
            socket = new Socket("127.0.0.1", 8888);
            thread = new Thread(new ChatThread());
            thread.start();
            dos = new DataOutputStream(socket.getOutputStream());
            dis = new DataInputStream(socket.getInputStream());
        } catch (UnknownHostException | IOException e) {
            e.printStackTrace();
        }
    }

    private void disconnected() {
        bConnected = false;
        try {
            if (dos != null) dos.close();
            if (dis != null) dis.close();
            if (socket != null) socket.close();
        } catch (IOException e1) {
            e1.printStackTrace();
        }
    }

    private class TfListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            String strMsg = tf.getText();
            tf.setText("");
            try {
                dos.writeUTF(strMsg);
                dos.flush();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
        }
    }

    private class ChatThread implements Runnable {
        @Override
        public void run() {
            try {
                bConnected = true;
                while (bConnected) {
                    String msg = dis.readUTF();
                    ta.setText(ta.getText() + msg + "\n");
                }
            } catch (SocketException e) {
                System.out.println("連線中斷");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

2. 聊天伺服器 - ChatServer

伺服器端使用 ServerSocket 監聽連線，每當有新客戶端接入，即啟動一條獨立執行緒處理該客戶的收發訊息，並將收到的訊息廣播給所有已連線的客戶端。

package com.panda.chat;

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

public class ChatServer {
    private boolean started = false;
    private List chatThreads = new ArrayList<>();

    public static void main(String[] args) {
        new ChatServer().startServer();
    }

    private void startServer() {
        try (ServerSocket seso = new ServerSocket(8888)) {
            started = true;
            System.out.println("伺服器已啟動，等待客戶端連線...");

            while (started) {
                Socket sos = seso.accept();
                System.out.println("一個客戶端已連線：" + sos.getInetAddress());

                ChatThread ct = new ChatThread(sos);
                chatThreads.add(ct);
                new Thread(ct).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private class ChatThread implements Runnable {
        private Socket socket;
        private DataInputStream din = null;
        private DataOutputStream don = null;
        private boolean bConnected = false;

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

        private void send(String strMsgIn) {
            try {
                don.writeUTF(strMsgIn);
                don.flush();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void run() {
            try {
                din = new DataInputStream(socket.getInputStream());
                don = new DataOutputStream(socket.getOutputStream());

                bConnected = true;
                while (bConnected) {
                    String strMsgIn = din.readUTF();
                    System.out.println("收到訊息：" + strMsgIn);

                    for (ChatThread ct : chatThreads) {
                        ct.send(strMsgIn);
                    }
                }
            } catch (IOException e) {
                try {
                    socket.close();
                    chatThreads.remove(this);
                    System.out.println("客戶端斷開連線，移除執行緒");
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            } finally {
                try {
                    if (din != null) din.close();
                    if (don != null) don.close();
                    if (socket != null) socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}