网络编程入门与网络寻址解析

### 网络编程入门与网络寻址解析 #### 一、网络编程入门 ##### 1. Java 8 实现回声服务器和客户端 传统的回声服务器使用 `while` 循环处理客户端请求： ```java String inputLine; while ((inputLine = br.readLine()) != null) { System.out.println("Client request: " + inputLine); out.println(inputLine); } ``` 使用 Java 8 的 `Supplier` 接口和 `Stream` 对象可以实现相同功能： ```java Supplier<String> socketInput = () -> { try { return br.readLine(); } catch (IOException ex) { return null; } }; Stream<String> stream = Stream.generate(socketInput); stream .map(s -> { System.out.println("Client request: " + s); out.println(s); return s; }) .allMatch(s -> s != null); ``` 客户端方面，传统的 `while` 循环： ```java while (true) { System.out.print("Enter text: "); String inputLine = scanner.nextLine(); if ("quit".equalsIgnoreCase(inputLine)) { break; } out.println(inputLine); String response = br.readLine(); System.out.println("Server response: " + response); } ``` 使用 Java 8 功能实现： ```java Supplier<String> scannerInput = () -> scanner.next(); System.out.print("Enter text: "); Stream.generate(scannerInput) .map(s -> { out.println(s); System.out.println("Server response: " + s); System.out.print("Enter text: "); return s; }) .allMatch(s -> !"quit".equalsIgnoreCase(s)); ``` 虽然这种实现比传统实现更长，但对于更复杂的问题可以提供更简洁的解决方案。 ##### 2. UDP 和多播 多播是一种定期向组发送消息的有用技术，使用 UDP 服务器和一个或多个 UDP 客户端。下面是创建多播服务器和客户端的示例： - **多播服务器** ```java public class MulticastServer { public static void main(String args[]) { System.out.println("Multicast Time Server"); DatagramSocket serverSocket = null; try { serverSocket = new DatagramSocket(); while (true) { String dateText = new Date().toString(); byte[] buffer = new byte[256]; buffer = dateText.getBytes(); InetAddress group = InetAddress.getByName("224.0.0.0"); DatagramPacket packet; packet = new DatagramPacket(buffer, buffer.length, group, 8888); serverSocket.send(packet); System.out.println("Time sent: " + dateText); try { Thread.sleep(1000); } catch (InterruptedException ex) { // Handle exception } } } catch (SocketException ex) { // Handle exception } catch (IOException ex) { // Handle exception } } } ``` - **多播客户端** ```java public class MulticastClient { public static void main(String args[]) { System.out.println("Multicast Time Client"); try (MulticastSocket socket = new MulticastSocket(8888)) { InetAddress group = InetAddress.getByName("224.0.0.0"); socket.joinGroup(group); System.out.println("Multicast Group Joined"); byte[] buffer = new byte[256]; DatagramPacket packet = new DatagramPacket(buffer, buffer.length); for (int i = 0; i < 5; i++) { socket.receive(packet); String received = new String(packet.getData()); System.out.println(received.trim()); } socket.leaveGroup(group); } catch (IOException ex) { // Handle exception } System.out.println("Multicast Time Client Terminated"); } } ``` 如果在 Mac