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Windows CE / PocketPC Java 網絡編程完整實戰：從 Socket 到 RMI 分布式開發

編輯：Java 程式設計入門

嵌入式設備時代的 Java 網絡編程，以 Windows CE / PocketPC 平台為例，完整展示從基礎 Socket 通訊到多層架構、RMI 分布式調用的實戰開發流程。

基礎 Client-Server Socket 通訊

Server 端實作

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

public class NetServer {
    private ServerSocket serverSocket;
    private Socket clientSocket;
    
    public NetServer() {
        try {
            serverSocket = new ServerSocket(900, 200); // 埠口 900，最大佇列 200
            System.out.println("Server 啟動，等待連線...");
            clientSocket = serverSocket.accept();
            System.out.println("客戶端連線: " + clientSocket.getInetAddress().getHostAddress());
        } catch (IOException e) {
            System.err.println("Server 異常: " + e.getMessage());
        }
    }
    
    public static void main(String[] args) {
        new NetServer();
    }
}

Client 端測試

PC 端啟動 Server 後，PocketPC 透過 telnet 127.0.0.1 900 即可建立連線驗證。

多執行緒回應式 Server：NetHelloServer

引入 Thread 處理併發，每個連線獨立執行緒：

public class NetHelloServer {
    public NetHelloServer() {
        try {
            ServerSocket serverSocket = new ServerSocket(900, 200);
            while (true) {
                Socket clientSocket = serverSocket.accept();
                new Thread(new ClientHandler(clientSocket)).start();
            }
        } catch (IOException e) {
            System.err.println("Server 異常: " + e.getMessage());
        }
    }
    
    static class ClientHandler implements Runnable {
        private Socket socket;
        ClientHandler(Socket socket) { this.socket = socket; }
        
        public void run() {
            try (DataInputStream in = new DataInputStream(socket.getInputStream());
                 DataOutputStream out = new DataOutputStream(socket.getOutputStream())) {
                
                out.writeUTF("請輸入您的姓名");
                String name = in.readUTF();
                out.writeUTF("收到: " + name + "，系統處理中...");
                out.writeUTF(name + " 您好！");
                System.out.println("Server 收到: " + name);
            } catch (IOException e) {
                System.err.println("處理異常: " + e.getMessage());
            } finally {
                try { socket.close(); } catch (IOException ignored) {}
            }
        }
    }
    
    public static void main(String[] args) { new NetHelloServer(); }
}

PocketPC 圖形化 Client：HelloClient

使用 AWT 建構簡易 GUI，包含姓名輸入、Server IP 設定、訊息顯示區、發送/離開按鈕：

public class HelloClient extends Frame {
    private TextField tfName, tfServerIp;
    private TextArea taMessages;
    private Socket socket;
    
    public HelloClient() {
        // GUI 初始化佈局代碼...
        btnSend.addMouseListener(new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                sendMessage();
            }
        });
    }
    
    private void sendMessage() {
        String name = tfName.getText().trim();
        String ip = tfServerIp.getText().trim();
        if (name.isEmpty() || ip.isEmpty()) return;
        
        try {
            socket = new Socket(ip, 900);
            DataInputStream in = new DataInputStream(socket.getInputStream());
            DataOutputStream out = new DataOutputStream(socket.getOutputStream());
            
            String msg = in.readUTF(); // "請輸入您的姓名"
            taMessages.append("Server: " + msg + "\n");
            
            out.writeUTF(name);
            String reply1 = in.readUTF(); // "收到: xxx..."
            taMessages.append("Server: " + reply1 + "\n");
            String reply2 = in.readUTF(); // "xxx 您好！"
            taMessages.append("Server: " + reply2 + "\n");
            
            socket.close();
        } catch (IOException ex) {
            taMessages.append("錯誤: " + ex.getMessage() + "\n");
        }
    }
    
    public static void main(String[] args) { new HelloClient(); }
}

三層架構：Socket + JDBC 整合 (NetDBServer)

架構分層：Client → Socket Server (業務邏輯) → JDBC → Database (HSQLDB)

class DBHandler extends Thread {
    private Socket socket;
    private static Connection conn;
    
    DBHandler(Socket socket) { this.socket = socket; }
    
    public void run() {
        try (DataInputStream in = new DataInputStream(socket.getInputStream());
             DataOutputStream out = new DataOutputStream(socket.getOutputStream())) {
            
            out.writeUTF("請輸入查詢代碼");
            String code = in.readUTF();
            
            // 初始化資料庫 (僅首次)
            if (!initialized) { initDatabase(); initialized = true; }
            
            // 查詢 Place 表
            try (Statement stmt = conn.createStatement();
                 ResultSet rs = stmt.executeQuery(
                     "SELECT Name FROM Place WHERE Code = " + code)) {
                String name = rs.next() ? rs.getString(1) : "查無資料";
                out.writeUTF("查詢結果: " + name);
            }
        } catch (Exception e) {
            System.err.println("DB 處理異常: " + e.getMessage());
        } finally {
            try { socket.close(); } catch (IOException ignored) {}
        }
    }
}

HTTP 客戶端：行動裝置網頁抓取

public class HttpTest extends Frame {
    private TextField tfUrl;
    private TextArea taContent;
    
    class FetchAction implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            try {
                URL url = new URL(tfUrl.getText());
                try (BufferedReader br = new BufferedReader(
                        new InputStreamReader(url.openStream()))) {
                    String line;
                    while ((line = br.readLine()) != null) {
                        taContent.append(line + "\n");
                    }
                }
            } catch (Exception ex) {
                taContent.append("錯誤: " + ex.getMessage());
            }
        }
    }
}

注意：原始 HTTP 回應為 HTML 原始碼，需自行解析渲染（JS、CSS、圖片等資源需額外下載處理），這正是瀏覽器引擎的核心複雜度所在。

RMI 分布式遠程方法調用

服務介面與實作

// 遠程介面
public interface CustWork extends Remote {
    String getSrvMsg() throws RemoteException;
}

// 服務實作
public class CustWorkImpl extends UnicastRemoteObject implements CustWork {
    public CustWorkImpl() throws RemoteException { super(); }
    
    public String getSrvMsg() throws RemoteException {
        String thread = Thread.currentThread().getName();
        String time = Calendar.getInstance().getTime().toString();
        System.out.println(thread + " : Client connected at " + time);
        return thread + " : Message from Server at " + time;
    }
}

Server 端啟動註冊

public class RMIServerBootstrap {
    public static void main(String[] args) {
        try {
            // 內建註冊中心 (埠口 1099)
            LocateRegistry.createRegistry(1099);
            CustWorkImpl service = new CustWorkImpl();
            Naming.rebind("myServer", service);
            System.out.println("RMI 服務已綁定: myServer");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Client 端調用

public class RMIClient {
    public static void main(String[] args) {
        try {
            if (System.getSecurityManager() == null) {
                System.setSecurityManager(new RMISecurityManager());
            }
            CustWork service = (CustWork) Naming.lookup(
                "rmi://192.168.0.1:1099/myServer");
            System.out.println("Server 回應: " + service.getSrvMsg());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

嵌入式 Java 開發關鍵差異

項目	J2SE 標準版	PersonalJava / J2ME (PocketPC)
編譯工具	javac	jdk1.1.8\bin\javac (需相容舊版)
Stub/Skeleton 生成	rmic	rmic -v1.1 (相容 1.1 協議)
執行命令	java	pjava (PersonalJava VM)
安全策略	java.policy	需手動配置 C:\jdk1.3.1\jre\lib\security\java.policy
部署檔案	.class / .jar	需包含 *_Stub.class 部署至裝置

編譯部署指令彙整

# Server 端 (PC)
javac -classpath %pjeeclasspath%;hsql.jar netDBServer.java
pjava -classpath %pjeeclasspath%;hsql.jar netDBServer

# Client 端 (PocketPC)
javac -classpath %pjeeclasspath% Client.java
pjava -classpath %pjeeclasspath% Client
# 再複製 .class 至 PocketPC 執行

從基礎 Socket 到 RMI 分布式架構，Windows CE / PocketPC 平台上的 Java 網絡編程展現了「Write Once, Run Anywhere」的跨平台威力。雖然嵌入式 JVM 版本較舊（PersonalJava 基於 JDK 1.1.x），但核心網絡 API 保持高度相容，配合無線網卡、藍牙、行動通訊模組，即可構建實用的行動企業應用系統。