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();
}
}