JAVA异步的UDP 通讯-服务端

1. 使用NIO实现非阻塞UDP通信

通过DatagramChannel和Selector，可以实现非阻塞的UDP通信，从而高效地处理多个客户端的请求。

示例代码：

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;

public class AsyncUDPServer {
    public static void main(String[] args) throws IOException {
        DatagramChannel channel = DatagramChannel.open();
        channel.configureBlocking(false);
        channel.bind(new InetSocketAddress(9898));

        Selector selector = Selector.open();
        channel.register(selector, SelectionKey.OP_READ);

        while (selector.select() > 0) {
            for (SelectionKey key : selector.selectedKeys()) {
                if (key.isReadable()) {
                    ByteBuffer buffer = ByteBuffer.allocate(1024);
                    channel.receive(buffer);
                    buffer.flip();
                    String message = new String(buffer.array(), 0, buffer.limit());
                    System.out.println("Received: " + message);

                    // 可以在此处处理消息并发送响应
                    String response = "Echo: " + message;
                    buffer.clear();
                    buffer.put(response.getBytes());
                    buffer.flip();
                    channel.send(buffer, key.channel().socket().getRemoteSocketAddress());
                }
                selector.selectedKeys().remove(key);
            }
        }
    }
}

2. 设置超时和缓冲区大小

为了优化性能，可以设置接收超时时间以及调整接收和发送缓冲区的大小。

示例代码：

import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;

public class OptimizedUDPServer {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(9898);
        socket.setSoTimeout(5000); // 设置接收超时时间为5000毫秒
        socket.setReceiveBufferSize(8192); // 设置接收缓冲区大小
        socket.setSendBufferSize(8192); // 设置发送缓冲区大小

        byte[] receiveBuffer = new byte[1024];
        DatagramPacket receivePacket = new DatagramPacket(receiveBuffer, receiveBuffer.length);

        while (true) {
            try {
                socket.receive(receivePacket);
                String message = new String(receivePacket.getData(), 0, receivePacket.getLength());
                System.out.println("Received: " + message);

                // 发送响应
                String response = "Echo: " + message;
                DatagramPacket sendPacket = new DatagramPacket(response.getBytes(), response.getBytes().length,
                        receivePacket.getAddress(), receivePacket.getPort());
                socket.send(sendPacket);
            } catch (Exception e) {
                System.out.println("Error: " + e.getMessage());
            }
        }
    }
}

3. 使用线程池处理请求

通过线程池可以高效地处理多个客户端的请求，避免阻塞主线程。

示例代码：

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ThreadedUDPServer {
    private static final ExecutorService executor = Executors.newFixedThreadPool(10);

    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(9898);

        while (true) {
            byte[] receiveBuffer = new byte[1024];
            DatagramPacket receivePacket = new DatagramPacket(receiveBuffer, receiveBuffer.length);
            socket.receive(receivePacket);

            executor.submit(() -> {
                try {
                    String message = new String(receivePacket.getData(), 0, receivePacket.getLength());
                    System.out.println("Received: " + message);

                    // 发送响应
                    String response = "Echo: " + message;
                    DatagramPacket sendPacket = new DatagramPacket(response.getBytes(), response.getBytes().length,
                            receivePacket.getAddress(), receivePacket.getPort());
                    socket.send(sendPacket);
                } catch (Exception e) {
                    System.out.println("Error: " + e.getMessage());
                }
            });
        }
    }
}

4. 异步处理和超时机制

在异步处理中，可以设置超时机制，以便在长时间未收到响应时进行处理。

示例代码：

import java.net.DatagramSocket;
import java.net.DatagramPacket;
import java.util.concurrent.*;

public class AsyncUDPServerWithTimeout {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(9898);
        ExecutorService executor = Executors.newSingleThreadExecutor();

        while (true) {
            byte[] receiveBuffer = new byte[1024];
            DatagramPacket receivePacket = new DatagramPacket(receiveBuffer, receiveBuffer.length);

            Future<String> future = executor.submit(() -> {
                socket.receive(receivePacket);
                return new String(receivePacket.getData(), 0, receivePacket.getLength());
            });

            try {
                String message = future.get(5, TimeUnit.SECONDS); // 设置超时时间为5秒
                System.out.println("Received: " + message);

                // 发送响应
                String response = "Echo: " + message;
                DatagramPacket sendPacket = new DatagramPacket(response.getBytes(), response.getBytes().length,
                        receivePacket.getAddress(), receivePacket.getPort());
                socket.send(sendPacket);
            } catch (TimeoutException e) {
                System.out.println("Timeout occurred. No data received within 5 seconds.");
            }
        }
    }
}