例10.1说明InetAddress类的用法的应用程序。
public class Example10_1 {
public static void main(String args[]) {
try {// 以下代码通过域名建立InetAddress对象：
InetAddress addr = InetAddress.getByName("www.fudan.edu.cn");
String domainName = addr.getHostName();// 获得主机名
String IPName = addr.getHostAddress();// 获得IP地址
System.out.println(domainName);
System.out.println(IPName);
} catch (UnknownHostException e) {
e.printStackTrace();
}
}
}
例10.2以数据流方式读取网页内容的应用程序。
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*; public class Example10_2 {
public static void main(String args[]) {
new DownNetFile();
}
} class DownNetFile extends JFrame implements ActionListener {
JTextField inField = new JTextField(30);
JTextArea showArea = new JTextArea();
JButton b = new JButton("下载");
JPanel p = new JPanel(); DownNetFile() {
super("读取网络文本文件示意程序");
Container con = this.getContentPane();
p.add(inField);
p.add(p);
JScrollPane jsp = new JScrollPane(showArea);
b.addActionListener(this);
con.add(p, "North");
con.add(jsp, "Center");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(500, 400);
setVisible(true);
} public void actionPerformed(ActionEvent e) {
readByURL(inField.getText());
} public void readByURL(String urlName) {
try {
URL url = new URL(urlName);// 由网址创建URL对象
URLConnection tc = url.openConnection();// 获得URLConnection对象
tc.connect();// 设置网络连接
InputStreamReader in = new InputStreamReader(tc.getInputStream());
BufferedReader dis = new BufferedReader(in);// 采用缓冲式输入
String inLine;
while ((inLine = dis.readLine()) != null) {
showArea.append(inLine + "\n");
}
dis.close();// 网上资源使用结束后，数据流及时关闭
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
/* 访问网上资源可能产生MalformedURLException和IOException异常 */
}
}
例10.3C/S模式中的Client端应用程序。
import java.io.*;
import java.net.*; public class Client {
public static void main(String args[]) {
String s = null;
Socket mySocket;
DataInputStream in = null;
DataOutputStream out = null;
try {
mySocket = new Socket("localhost", 4441);// 本地机IP地址
in = new DataInputStream(mySocket.getInputStream());
out = new DataOutputStream(mySocket.getOutputStream());
out.writeUTF("服务器，你好");// 通过out向“线路”写入信息
while (true) {
s = in.readUTF();// 通过使用in读取服务器放入“线路”里的信息
if (s == null) {
break;// 输入无信息结束输入
} else {
System.out.print(s);
}
}
mySocket.close();// 关闭Socket
} catch (IOException e) {
System.out.print("无法连接");
}
}
}
例10.4与例10.3Client端应用程序对应的Server端应用程序。
import java.io.*;
import java.net.*; public class Server {
public static void main(String args[]) {
ServerSocket server = null;
Socket you = null;
String s = null;
DataOutputStream out = null;
DataInputStream in = null;
try {
server = new ServerSocket(4441);
} catch (IOException e1) {
System.out.print("ERROR:" + e1);
}
try {
you = server.accept();
in = new DataInputStream(you.getInputStream());
out = new DataOutputStream(you.getOutputStream());
while (true) {
s = in.readUTF();// 通过使用in读取客户放入“线路”里的信息
if (s != null) {
break;
}
}
out.writeUTF("客户，你好，我是服务器");// 通过out向“线路”写入信息
out.close();
} catch (IOException e) {
System.out.print("ERRO:" + e);
}
}
}
例10.5将套接字连接工作置于线程的客户端小应用程序。
import java.net.*;
import java.io.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.applet.*; public class Aclient extends Applet implements Runnable, ActionListener {
JButton button;
JTextField textF;
JTextArea textA;
Socket socket;
Thread thread;
DataInputStream in;
DataOutputStream out; public void init() {
setBackground(new Color(120, 153, 137));
setLayout(new BorderLayout());
button = new JButton("发送消息");
textF = new JTextField(20);
textA = new JTextArea(20, 30);
setSize(450, 350);
JPanel p = new JPanel();
p.add(textF);
p.add(button);
add(textA, "Center");
add(p, "South");
button.addActionListener(this);
} public void start() {
try {
socket = new Socket(this.getCodeBase().getHost(), 4441);
in = new DataInputStream(socket.getInputStream());
out = new DataOutputStream(socket.getOutputStream());
} catch (IOException e) {
}
if (thread == null) {
thread = new Thread(this);
thread.setPriority(Thread.MIN_PRIORITY);
thread.start();
}
} public void run() {
String s = null;
while (true) {
try {
s = in.readUTF();/* 通过in读取服务器放入“线路”里的信息 */
} catch (IOException e) {
}
if (s.equals("结束")) {
try {
socket.close();
break;
} catch (IOException e) {
}
} else {
textA.append(s + "\n");
}
}
} public void actionPerformed(ActionEvent e) {
if (e.getSource() == button) {
String s = textF.getText();
if (s != null) {
try {
out.writeUTF(s);
} catch (IOException e1) {
}
} else {
try {
out.writeUTF("请说话");
} catch (IOException e1) {
}
}
}
}
}
例10.6对应例10.5客户端小应用程序的服务器端小应用程序。
import java.io.*;
import java.net.*;
import java.util.*; public class Aserver {
public static void main(String args[]) {
ServerSocket server = null;
ServerThread thread;
Socket client = null;
while (true) {
try {
server = new ServerSocket(4331);
} catch (IOException e1) {
System.out.println("监听时发现错误" + "ERROR:" + e1);
}
try {
client = server.accept();
} catch (IOException e1) {
System.out.println("正在等待客户时，出错！");
}
if (client != null) {
new ServerThread(client).start();
} else {
continue;// 继续等待客户呼叫
}
}
}
} class ServerThread extends Thread {
Socket socket;
String s = null;
DataOutputStream out = null;
DataInputStream in = null; ServerThread(Socket t) {
socket = t;// 参照t创建输入流和输出流
try {
in = new DataInputStream(t.getInputStream());
out = new DataOutputStream(t.getOutputStream());
} catch (IOException e) {
}
} public void run() {
while (true) {
try {
s = in.readUTF();// 通过in读取客户放入“线路”里的信息
} catch (IOException e) {
System.out.println("ERROR:" + e);
}
try {
if (s.equals("结束"))// 客户离开，服务器也离开
{
out.writeUTF(s);
socket.close();
} else {
try {
out.writeUTF("我是服务器你对我说：" + s);
// 通过out向写入“线路”回复信息
} catch (IOException e) {
}
}
} catch (IOException e) {
}
}
}
}