第35 章 ： 网络编程
152 网络编程简介
网络编程: 多台主机之间的数据通信
通信协议：IP、TCP（可靠数据连接）、UDP（不可靠数据连接）
网络程序模型:
C/S Client/Server 客户端/服务端 安全性高 开发成本高
B/S Browser/Server 浏览器/服务器 安全性较低 开发成本低
目前以B/S 结构为主
153 Echo程序模型
ServerSocket与Socket
ServerSocket 设置服务器监听端口
Socket 设置要连接服务器的ip和端口
实现一个客户端与服务器端通信 Echo服务
Server.java
import java.io.IOException; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; import java.util.Scanner; public class Server { public static void main(String[] args) throws IOException { // 设置服务器监听端口 ServerSocket server = new ServerSocket(8080); System.out.println("服务启动。。。"); // 接收客户端连接 Socket client = server.accept(); // 接收客户端消息 Scanner scanner = new Scanner(client.getInputStream()); scanner.useDelimiter("\n"); // 发送给客户端数据 PrintWriter out = new PrintWriter(client.getOutputStream()); // 结束标志 boolean flag = true; while (flag) { if (scanner.hasNext()) { // 读取客户端数据 String message = scanner.next(); System.out.println("收到: " + message); // 结束标志 if ("bye".equalsIgnoreCase(message)) { flag = false; } // 发送数据给客户端 out.println("[echo] " + message); out.flush(); } } // 关闭 out.close(); scanner.close(); client.close(); server.close(); } }
Client.java
import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.Socket; import java.util.Scanner; public class Client { private final static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); public static void main(String[] args) throws IOException { // 连接服务器 Socket client = new Socket("localhost", 8080); // 接收服务器信息 Scanner scanner = new Scanner(client.getInputStream()); scanner.useDelimiter("\n"); // 向服务器发送信息 PrintWriter out = new PrintWriter(client.getOutputStream()); // 结束标志 boolean flag = true; while (flag) { // 读取控制台输入，发送给服务器 String message = getInput("请输入："); System.out.println("发送：" + message); out.println(message); out.flush(); // 接收服务端返回的数据 if (scanner.hasNext()) { System.out.println("返回：" + scanner.next()); } // 结束标志 if ("bye".equalsIgnoreCase(message)) { flag = false; } } // 关闭操作 out.close(); scanner.close(); client.close(); } // 接收控制台输入 public static String getInput(String prompt) throws IOException { System.out.println(prompt); return reader.readLine(); } }
154 BIO处理模型
多线程接收多个客户端连接
只用修改服务端代码
Server.java
import java.io.IOException; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; import java.util.Scanner; public class Server { public static class ClientThread implements Runnable { private Socket client = null; private Scanner scanner = null; private PrintWriter out = null; private boolean flag = true; // 结束标志 ClientThread(Socket client) throws IOException { this.client = client; // 接收客户端消息 this.scanner = new Scanner(client.getInputStream()); this.scanner.useDelimiter("\n"); // 发送给客户端数据 this.out = new PrintWriter(client.getOutputStream()); } @Override public void run() { while (this.flag) { if (this.scanner.hasNext()) { // 读取客户端数据 String message = this.scanner.next(); System.out.println("收到: " + Thread.currentThread() + message); // 结束标志 if ("bye".equalsIgnoreCase(message)) { this.flag = false; } // 发送数据给客户端 this.out.println("[echo] " + message); this.out.flush(); } } this.out.close(); this.scanner.close(); try { this.client.close(); } catch (IOException e) { e.printStackTrace(); } } } public static void main(String[] args) throws IOException { // 设置服务器监听端口 ServerSocket server = new ServerSocket(8080); System.out.println("服务启动。。。"); while (true) { // 接收客户端连接 Socket client = server.accept(); new Thread(new ClientThread(client)).start(); } // 关闭 // server.close(); } }
155 UDP程序
UDP 基于数据报实现
TCP要保证可靠连接，需要的服务器资源就多
不管客户端是否接收到
Receiver.java
import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; public class Receiver { public static void main(String[] args) throws IOException { DatagramSocket receiver = new DatagramSocket(9000); byte[] data = new byte[2014]; DatagramPacket packet = new DatagramPacket(data, data.length); // 等待接收数据 receiver.receive(packet); System.out.println(new String(data, 0, packet.getLength())); // 关闭 receiver.close(); } }
Sender.java
import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; public class Sender { public static void main(String[] args) throws Exception { DatagramSocket sender = new DatagramSocket(9001); // 发送数据 String message = "Hello world"; DatagramPacket packet = new DatagramPacket(message.getBytes(), 0, message.length(), InetAddress.getByName("localhost"), 9000); sender.send(packet); // 关闭 sender.close(); } }
