Java网络编程BIO示例，从简单到伪异步逐渐升级

Java基础ServerSocket、Socket服务端客户端通信的示例，从简单到伪异步逐渐升级。

简单示例

最加单的示例，客户端向服务端发送一个消息就结束。

服务端代码：

/**
 * 服务端
 *
 * @Author wanglingqiang
 * @Date 2020/7/3 下午5:53
 **/
public class Server {

    public static void main(String[] args) throws IOException {
        // 开启服务，绑定端口
        ServerSocket serverSocket = new ServerSocket(6379);
        // 同步阻塞等待消息
        Socket socket = serverSocket.accept();
        // new一个数组容器
        byte[] bytes = new byte[1024];
        // 获得输入流
        InputStream inputStream = socket.getInputStream();
        // 把输入流的数据读到字节数组容器
        inputStream.read(bytes);
        // 字节数组转成字符串
        String msg = new String(bytes);
        // 打印
        System.out.println(msg);
        // 关闭
        inputStream.close();
        socket.close();
        serverSocket.close();
    }
}

客户端代码：

/**
 * 客户端代码
 *
 * @Author wanglingqiang
 * @Date 2020/7/3 下午5:57
 **/
public class Client {
    public static void main(String[] args) throws IOException {
        // 连上Server
        Socket socket = new Socket("127.0.0.1", 6379);
        // 获得输出流
        OutputStream outputStream = socket.getOutputStream();
        // 消息
        String msg = "Hello world.";
        // 向输出流写字节数据
        outputStream.write(msg.getBytes());
        // 关闭
        outputStream.close();
        socket.close();
    }
}

运行服务端代码，然后运行客户端代码。服务端控制台输出：

Hello world.

升级示例：伪异步

示例一中accept()接收到客户端请求后，后面的读写的操作是同步进行的，在下面的示例中我们对此做升级，用一个线程池处理读写任务。

服务端代码：

/**
 * TODO
 *
 * @author wanglingqiang
 * @date 2020/12/9 下午2:57
 */
public class Server {

    private static ExecutorService threadPool = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket();
        serverSocket.bind(new InetSocketAddress(6379));
        System.out.println("Server started.");
        try {
            while (true) {
                threadPool.execute(new ServerTask(serverSocket.accept()));
            }
        } finally {
            serverSocket.close();
        }
    }

    private static class ServerTask implements Runnable {
        private Socket socket;

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

        @Override
        public void run() {
            try (ObjectInputStream inputStream = new ObjectInputStream(socket.getInputStream());
                 ObjectOutputStream outputStream = new ObjectOutputStream(socket.getOutputStream())) {
                String msg = inputStream.readUTF();
                System.out.println("服务端收到：" + msg);
                outputStream.writeUTF("success");
                outputStream.flush();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (socket != null) {
                    try {
                        socket.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}

客户端代码：

/**
 * TODO
 *
 * @author wanglingqiang
 * @date 2020/12/9 下午3:01
 */
public class Client {
    public static void main(String[] args) throws IOException {
        Socket socket = null;
        ObjectOutputStream outputStream = null;
        ObjectInputStream inputStream = null;
        try {
            socket = new Socket();
            InetSocketAddress endpoint = new InetSocketAddress("127.0.0.1", 6379);
            socket.connect(endpoint);
            outputStream = new ObjectOutputStream(socket.getOutputStream());
            inputStream = new ObjectInputStream(socket.getInputStream());
            outputStream.writeUTF("Hello world.");
            outputStream.flush();
            String response = inputStream.readUTF();
            System.out.println(response);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (socket != null) socket.close();
            if (outputStream != null) outputStream.close();
            if (inputStream != null) inputStream.close();
        }
    }

升级示例，做到了对每个客户端开启一个线程做连接后的读写操作，实现伪异步的BIO。但始终还是BIO，accept()、write()、read()方法还是同步的，想做到真正的异步要用NIO。