Java 网络编程深度解析：从 Socket 到多线程通信实战

arduino复制编辑             ┌─────────────┐
             │   Client    │
             └────┬────────┘
                  │ Socket
             ┌────▼────┐
             │  网络   │
             └────┬────┘
                  │ ServerSocket
             ┌────▼────┐
             │  Server │
             └─────────┘

java复制编辑ServerSocket serverSocket = new ServerSocket(8888);
Socket clientSocket = serverSocket.accept(); // 阻塞等待连接
InputStream in = clientSocket.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String msg = reader.readLine();
System.out.println("收到客户端信息：" + msg);

java复制编辑Socket socket = new Socket("localhost", 8888);
OutputStream out = socket.getOutputStream();
PrintWriter writer = new PrintWriter(out, true);
writer.println("Hello Server!");

arduino复制编辑Client                       Server
  ↓                            ↓
创建 Socket                创建 ServerSocket
  ↓                            ↓
连接 Server（connect）      接收连接（accept）
  ↓                            ↓
发送数据 →→→→→→→→→→→→→→→ 接收数据
  ←←←←←←←←←←←←←←← 发送响应
关闭连接                    关闭连接

java复制编辑while (true) {
    Socket client = serverSocket.accept();
    new Thread(() -> handleClient(client)).start();
}

java复制编辑public void handleClient(Socket client) {
    try (BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()))) {
        String msg;
        while ((msg = in.readLine()) != null) {
            System.out.println("收到：" + msg);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

java复制编辑DatagramSocket socket = new DatagramSocket();
byte[] data = "Hello UDP".getBytes();
DatagramPacket packet = new DatagramPacket(data, data.length, InetAddress.getByName("localhost"), 9999);
socket.send(packet);

java复制编辑DatagramSocket socket = new DatagramSocket(9999);
byte[] buf = new byte[1024];
DatagramPacket packet = new DatagramPacket(buf, buf.length);
socket.receive(packet);
System.out.println("接收到 UDP 数据：" + new String(packet.getData(), 0, packet.getLength()));

lua复制编辑       +----------------------+             +------------------+
       |      TCP 应用         |             |    UDP 应用       |
       +----------------------+             +------------------+
       | HTTP / HTTPS          |             | 在线游戏          |
       | 文件传输（FTP）       |             | 实时语音通话      |
       | 远程登录（SSH）       |             | 视频会议          |
       +----------------------+             +------------------+

java复制编辑ExecutorService threadPool = Executors.newCachedThreadPool();
while (true) {
    Socket client = serverSocket.accept();
    threadPool.execute(() -> handleClient(client));
}

java复制编辑FileInputStream fis = new FileInputStream("file.txt");
OutputStream out = socket.getOutputStream();
byte[] buffer = new byte[1024];
int len;
while ((len = fis.read(buffer)) != -1) {
    out.write(buffer, 0, len);
}

java复制编辑InputStream in = client.getInputStream();
FileOutputStream fos = new FileOutputStream("recv.txt");
byte[] buffer = new byte[1024];
int len;
while ((len = in.read(buffer)) != -1) {
    fos.write(buffer, 0, len);
}

java复制编辑List<Socket> clientList = new CopyOnWriteArrayList<>();

java复制编辑for (Socket s : clientList) {
    new PrintWriter(s.getOutputStream(), true).println(msg);
}

java复制编辑Selector selector = Selector.open();
ServerSocketChannel serverChannel = ServerSocketChannel.open();
serverChannel.bind(new InetSocketAddress(8888));
serverChannel.configureBlocking(false);
serverChannel.register(selector, SelectionKey.OP_ACCEPT);

arduino复制编辑Server                             Client
 ┌──────────────┐                 ┌──────────────┐
 │ ServerSocket │                 │    Socket    │
 └──────┬───────┘                 └──────┬───────┘
        │ 接受连接                        │ 连接服务器
 ┌──────▼───────┐                ┌───────▼────────┐
 │ 多线程处理器 │ ←─────────────→│ 数据发送/接收 │
 └──────────────┘                └────────────────┘