Java从入门到实战之（26）Java网络实例之练习

1、获取指定主机的IP地址

如何使用 InetAddress 类的 InetAddress.getByName() 方法来获取指定主机（网址）的IP地址？

package Java_Learn.File;

import java.net.InetAddress;
import java.net.UnknownHostException;

public class Main1 {
    public static void main(String[] args) {
        System.out.println(getIp("www.baidu.com"));
    }
    public static String getIp(String nds)
    {
        InetAddress address=null;
        try {
            address=InetAddress.getByName(nds);
        } catch (UnknownHostException e) {
            System.exit(2);
        }
        return  address.getHostName()+"="+address.getHostAddress();
    }
}

结果：

"C:Program FilesJavajdk1.8.0_221injava.exe" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3libidea_rt.jar=52053:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3in" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_221jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_221jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_221jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_221jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_221jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_221jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_221jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_221jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_221jrelibext
ashorn.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_221jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_221jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_221jrelibjce.jar;C:Program FilesJavajdk1.8.0_221jrelibjfr.jar;C:Program FilesJavajdk1.8.0_221jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_221jrelibjsse.jar;C:Program FilesJavajdk1.8.0_221jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_221jrelibplugin.jar;C:Program FilesJavajdk1.8.0_221jrelib
esources.jar;C:Program FilesJavajdk1.8.0_221jrelib
t.jar;C:appWorkSpace	argetclasses;C:Program Files (x86)scalalibscala-actors-2.11.0.jar;C:Program Files (x86)scalalibscala-actors-migration_2.11-1.1.0.jar;C:Program Files (x86)scalalibscala-library.jar;C:Program Files (x86)scalalibscala-parser-combinators_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-reflect.jar;C:Program Files (x86)scalalibscala-swing_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-xml_2.11-1.0.1.jar;C:
epositoryorgscala-langscala-library2.11.0scala-library-2.11.0.jar" Java_Learn.File.Main1
www.baidu.com=163.177.151.109

Process finished with exit code 0

2、判断端口是否可用

package Java_Learn.File;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;
import java.net.SocketTimeoutException;
public class Main1 {
    public static void main(String[] args) {
        printLog(isSocketAliveUitlitybyCrunchify("localhost",80));
        printLog(isSocketAliveUitlitybyCrunchify("localhost",8080));
        // 检测本地 8081 端口
        printLog(isSocketAliveUitlitybyCrunchify("localhost", 8081));

        // 检测 runoob.com 的 80 端口
        printLog(isSocketAliveUitlitybyCrunchify("runoob.com", 80));

        // 检测 runoob.com 的 443 端口
        printLog(isSocketAliveUitlitybyCrunchify("runoob.com", 443));

        // 检测 runoob.com 的 81 端口
        printLog(isSocketAliveUitlitybyCrunchify("runoob.com", 81));
    }
    public static boolean isSocketAliveUitlitybyCrunchify(String hostname,int port)
    {
        boolean isAlive=false;
        SocketAddress socketAddress=new InetSocketAddress(hostname,port);
        Socket socket=new Socket();
        int timeout=2000;
        printLog("hostName: " + hostname + ", port: " + port);
        try {
            socket.connect(socketAddress,timeout);
            socket.close();
            isAlive=true;
        }
        catch (SocketTimeoutException ex)
        {
            System.out.println("SocketTimeoutException " + hostname + ":" + port + ". " + ex.getMessage());
        }
        catch (IOException e) {
            System.out.println(
                    "IOException - 不能连接 " + hostname + ":" + port + ". " + e.getMessage());
        }
        return isAlive;
    }
    public  static void printLog(String str)
    {
        System.out.println(str);
    }
    public static void printLog(Boolean isAlive)
    {
        System.out.println("是否真正在使用:"+isAlive+"
");
    }
}

结果：

"C:Program FilesJavajdk1.8.0_221injava.exe" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3libidea_rt.jar=52421:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3in" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_221jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_221jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_221jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_221jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_221jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_221jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_221jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_221jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_221jrelibext
ashorn.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_221jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_221jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_221jrelibjce.jar;C:Program FilesJavajdk1.8.0_221jrelibjfr.jar;C:Program FilesJavajdk1.8.0_221jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_221jrelibjsse.jar;C:Program FilesJavajdk1.8.0_221jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_221jrelibplugin.jar;C:Program FilesJavajdk1.8.0_221jrelib
esources.jar;C:Program FilesJavajdk1.8.0_221jrelib
t.jar;C:appWorkSpace	argetclasses;C:Program Files (x86)scalalibscala-actors-2.11.0.jar;C:Program Files (x86)scalalibscala-actors-migration_2.11-1.1.0.jar;C:Program Files (x86)scalalibscala-library.jar;C:Program Files (x86)scalalibscala-parser-combinators_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-reflect.jar;C:Program Files (x86)scalalibscala-swing_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-xml_2.11-1.0.1.jar;C:
epositoryorgscala-langscala-library2.11.0scala-library-2.11.0.jar" Java_Learn.File.Main1
hostName: localhost, port: 80
IOException - 不能连接 localhost:80. Connection refused: connect
是否真正在使用:false

hostName: localhost, port: 8080
IOException - 不能连接 localhost:8080. Connection refused: connect
是否真正在使用:false

hostName: localhost, port: 8081
IOException - 不能连接 localhost:8081. Connection refused: connect
是否真正在使用:false

hostName: runoob.com, port: 80
是否真正在使用:true

hostName: runoob.com, port: 443
SocketTimeoutException runoob.com:443. connect timed out
是否真正在使用:false

hostName: runoob.com, port: 81
SocketTimeoutException runoob.com:81. connect timed out
是否真正在使用:false


Process finished with exit code 0

3、

如何使用 InetAddress 类的 InetAddress.getByName() 方法来获取指定主机（网址）的IP地址

package Java_Learn.File;

import java.net.InetAddress;
import java.net.UnknownHostException;

public class Main1 {
    public static void main(String[] args) {
        getIpAndHostname("本机信息");
    }
    private static void getIpAndHostname(String hostname)
    {
        try {
            InetAddress address =InetAddress.getLocalHost();
            System.out.println("本机地址："+address.getHostAddress()+"
"+"本机机名:"+address.getHostName());
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

结果：

Local HostAddress: 192.168.1.4
Local host name: harsh

4、获取远程文件大小

如何获取远程文件的大小？

package Java_Learn.File;

import java.io.IOException;
import java.net.*;

public class Main1 {
    public static void main(String[] args) {
        getRemoteFileSize("http://www.runoob.com/wp-content/themes/runoob/assets/img/newlogo.png");
    }
    private static void getRemoteFileSize(String str)
    {
        int size;
        try {
            URL url=new URL(str);
            URLConnection conn=url.openConnection();
            size=conn.getContentLength();
            if(size<0)
            {
                System.out.println("无法获取文件的大小");
            }
            else
            {
                System.out.println("文件大小为："+size+"bytes");
            }
            conn.getInputStream().close();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

结果：

"C:Program FilesJavajdk1.8.0_221injava.exe" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3libidea_rt.jar=53125:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3in" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_221jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_221jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_221jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_221jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_221jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_221jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_221jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_221jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_221jrelibext
ashorn.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_221jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_221jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_221jrelibjce.jar;C:Program FilesJavajdk1.8.0_221jrelibjfr.jar;C:Program FilesJavajdk1.8.0_221jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_221jrelibjsse.jar;C:Program FilesJavajdk1.8.0_221jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_221jrelibplugin.jar;C:Program FilesJavajdk1.8.0_221jrelib
esources.jar;C:Program FilesJavajdk1.8.0_221jrelib
t.jar;C:appWorkSpace	argetclasses;C:Program Files (x86)scalalibscala-actors-2.11.0.jar;C:Program Files (x86)scalalibscala-actors-migration_2.11-1.1.0.jar;C:Program Files (x86)scalalibscala-library.jar;C:Program Files (x86)scalalibscala-parser-combinators_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-reflect.jar;C:Program Files (x86)scalalibscala-swing_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-xml_2.11-1.0.1.jar;C:
epositoryorgscala-langscala-library2.11.0scala-library-2.11.0.jar" Java_Learn.File.Main1
文件大小为：278bytes

Process finished with exit code 0

5、Socket 实现多线程服务器程序

如何使用 Socket 类的 accept() 方法和 ServerSocket 类的 MultiThreadServer(socketname) 方法来实现多线程服务器程序？

package Java_Learn.File;

import java.io.IOException;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Main1 implements Runnable{
    Socket socket;
    public Main1(Socket socket) {
        this.socket = socket;
    }
    @Override
    public void run() {
        try {
            PrintStream printStream=new PrintStream(socket.getOutputStream());
            for(int i=100;i>=0;i--)
            {
                printStream.println(i+" bottles of beer on the wall");
            }
            printStream.close();
            socket.close();
        } catch (IOException e) {
            System.out.println(e.getMessage());
        }
    }
    private static void getThread(int port)
    {
        try {
            ServerSocket serverSocket=new ServerSocket(port);
            System.out.println("开始监听");
            while (true)
            {
                Socket socket=serverSocket.accept();
                System.out.println("已经连接上");
                new Thread(new Main1(socket)).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static void main(String[] args) {
        getThread(1234);
    }
}

结果：

Listening
Connected

6、查看主机指定文件的最后修改时间

如何查看主机指定文件的最后修改时间？

import java.net.URL;
import java.net.URLConnection;
import java.util.Date;
import java.text.SimpleDateFormat;
 
public class Main {
    public static void main(String[] argv) throws Exception {
        URL u = new URL("http://127.0.0.1/test/test.html");
        URLConnection uc = u.openConnection();
        SimpleDateFormat ft = new SimpleDateFormat ("yyyy-MM-dd hh:mm:ss");
        uc.setUseCaches(false);
        long timestamp = uc.getLastModified();
        System.out.println("test.html 文件最后修改时间 :" + ft.format(new Date(timestamp)));
    }
}

结果：

test.html 文件最后修改时间 :2018-09-06 10:06:04

7、使用 Socket 连接到指定主机

如何使用 net.Socket 类的 getInetAddress() 方法来连接到指定主机

import java.net.InetAddress;
import java.net.Socket;
 
public class WebPing {
    public static void main(String[] args) {
        try {
            InetAddress addr;
            Socket sock = new Socket("www.runoob.com", 80);
            addr = sock.getInetAddress();
            System.out.println("连接到 " + addr);
            sock.close();
        } catch (java.io.IOException e) {
            System.out.println("无法连接 " + args[0]);
            System.out.println(e);
        }
    }
}

结果：

连接到 http:/www.runoob.com/222.73.134.120

8、网页抓取

如何使用 net.URL 类的 URL() 构造函数来抓取网页？

package Java_Learn.File;

import java.io.*;
import java.net.MalformedURLException;
import java.net.URL;

public class Main1
{
    public static void main(String[] args) {
        getWeb("http://www.runoob.com");
    }
private static void getWeb(String webSite)
{
    try {
        URL url=new URL(webSite);
        BufferedReader reader=new BufferedReader(new InputStreamReader(url.openStream()));
        BufferedWriter writer=new BufferedWriter(new FileWriter("data.html"));
        String line;
        while ((line = reader.readLine()) != null)
        {
            System.out.println(line);
            writer.write(line);
            writer.newLine();
        }
        reader.close();
        writer.close();
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
}

结果：

"C:Program FilesJavajdk1.8.0_221injava.exe" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3libidea_rt.jar=53619:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3in" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_221jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_221jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_221jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_221jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_221jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_221jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_221jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_221jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_221jrelibext
ashorn.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_221jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_221jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_221jrelibjce.jar;C:Program FilesJavajdk1.8.0_221jrelibjfr.jar;C:Program FilesJavajdk1.8.0_221jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_221jrelibjsse.jar;C:Program FilesJavajdk1.8.0_221jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_221jrelibplugin.jar;C:Program FilesJavajdk1.8.0_221jrelib
esources.jar;C:Program FilesJavajdk1.8.0_221jrelib
t.jar;C:appWorkSpace	argetclasses;C:Program Files (x86)scalalibscala-actors-2.11.0.jar;C:Program Files (x86)scalalibscala-actors-migration_2.11-1.1.0.jar;C:Program Files (x86)scalalibscala-library.jar;C:Program Files (x86)scalalibscala-parser-combinators_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-reflect.jar;C:Program Files (x86)scalalibscala-swing_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-xml_2.11-1.0.1.jar;C:
epositoryorgscala-langscala-library2.11.0scala-library-2.11.0.jar" Java_Learn.File.Main1
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html>
<head><title>301 Moved Permanently</title></head>
<body bgcolor="white">
<h1>301 Moved Permanently</h1>
<p>The requested resource has been assigned a new permanent URI.</p>
<hr/>Powered by Tengine</body>
</html>

Process finished with exit code 0

9、获取 URL响应头的日期信息

如何使用 HttpURLConnection 的 httpCon.getDate() 方法来获取 URL响应头的日期信息？

import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Date;
 
public class Main{
   public static void main(String args[]) 
   throws Exception {
      URL url = new URL("http://www.runoob.com");
      HttpURLConnection httpCon = 
      (HttpURLConnection) url.openConnection();
      long date = httpCon.getDate();
      if (date == 0)
      System.out.println("无法获取信息。");
      else
      System.out.println("Date: " + new Date(date));
   }
}

结果：

Date: Mon May 04 11:57:06 CST 2015

10、获取 URL 响应头信息

如何获取指定 URL 的响应头信息？

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Map;
import java.util.Set;
 
public class Main {
    public static void main(String[] args) throws IOException{
        URL url = new URL("http://www.runoob.com");
        URLConnection conn = url.openConnection();
        
        Map headers = conn.getHeaderFields();
        Set<String> keys = headers.keySet();
        for( String key : keys ){
            String val = conn.getHeaderField(key);
            System.out.println(key+"    "+val);
        }
        System.out.println( conn.getLastModified() );
    }
}

结果：

Transfer-Encoding    chunked
null    HTTP/1.1 200 OK
Server    Tengine/1.3.0
Connection    keep-alive
Vary    Cookie
Date    Mon, 04 May 2015 03:54:05 GMT
X-Pingback    http://www.runoob.com/xmlrpc.php
X-Powered-By    PHP/5.3.15
Content-Type    text/html; charset=UTF-8

11、解析URL

如何使用 net.URL 类的 url.getProtocol() ,url.getFile() 等方法来解析 URL 地址？

import java.net.URL;
 
public class Main {
   public static void main(String[] args) 
   throws Exception {
      URL url = new URL("http://www.runoob.com/html/html-tutorial.html");
      System.out.println("URL 是 " + url.toString());
      System.out.println("协议是 " + url.getProtocol());
      System.out.println("文件名是 " + url.getFile());
      System.out.println("主机是 " + url.getHost());
      System.out.println("路径是 " + url.getPath());
      System.out.println("端口号是 " + url.getPort());
      System.out.println("默认端口号是 " 
      + url.getDefaultPort());
   }
}

结果：

URL 是 http://www.runoob.com/html/html-tutorial.html
协议是 http
文件名是 /html/html-tutorial.html
主机是 www.runoob.com
路径是 /html/html-tutorial.html
端口号是 -1
默认端口号是 80

12、ServerSocket 和 Socket 通信实例

如何实现客户端发送消息到服务器，服务器接收到消息并读取输出，然后写出到客户端客户端接收到输出。

1、建立服务器端

• 服务器建立通信ServerSocket
• 服务器建立Socket接收客户端连接
• 建立IO输入流读取客户端发送的数据
• 建立IO输出流向客户端发送数据消息

服务器端代码:

Server.java 文件

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
 
public class Server {
   public static void main(String[] args) {
      try {
         ServerSocket ss = new ServerSocket(8888);
         System.out.println("启动服务器....");
         Socket s = ss.accept();
         System.out.println("客户端:"+s.getInetAddress().getLocalHost()+"已连接到服务器");
         
         BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
         //读取客户端发送来的消息
         String mess = br.readLine();
         System.out.println("客户端："+mess);
         BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
         bw.write(mess+"
");
         bw.flush();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

以上代码运行输出结果为：

启动服务器....

2、建立客户端

• 创建Socket通信，设置通信服务器的IP和Port
• 建立IO输出流向服务器发送数据消息
• 建立IO输入流读取服务器发送来的数据消息

客户端代码:

Client.java 文件

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;
 
public class Client {
   public static void main(String[] args) {
      try {
         Socket s = new Socket("127.0.0.1",8888);
         
         //构建IO
         InputStream is = s.getInputStream();
         OutputStream os = s.getOutputStream();
         
         BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os));
         //向服务器端发送一条消息
         bw.write("测试客户端和服务器通信，服务器接收到消息返回到客户端
");
         bw.flush();
         
         //读取服务器返回的消息
         BufferedReader br = new BufferedReader(new InputStreamReader(is));
         String mess = br.readLine();
         System.out.println("服务器："+mess);
      } catch (UnknownHostException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

以上代码运行输出结果为：

服务器：测试客户端和服务器通信，服务器接收到消息返回到客户端