2019-06-04 Java学习日记之网络编程

网络编程三要素之IP概述：

每个设备在网络中的唯一标识

每台网络终端在网络中都要一个独立的地址，我们在网络中传输数据就是使用这个地址

ipconfig：查看本机IP

ping：测试连接

本地回路地址：127.0.0.1  255.255.255.255是广播地址

IPv4：4个字节组成，4和0-255、大概42亿，30亿都在北美，亚洲4亿。2011年初已经用尽

IPv6：8组，每组4个16进制数

1a2b:0000:aaaa:0000:0000:0000:aabb:1f2f

1a2b::aaaa:0000:0000:0000:aabb:1f2f

1a2b:0000:aaaa::aabb:1f2f

1a2b:0000:aaaa::0000:aabb:1f2f

1a2b:0000:aaaa:0000::aabb:1f2f

网络编程三要素之端口号概述：

每个程序在设备上的唯一标识

每个网络程序都需要绑定一个端口号，传输数据的时候除了确定发到哪台机器上海要明确发到哪个程序

端口号范围从0-65535

编写网络应用就需要绑定一个端口号，尽量使用1024以上的，1024以下的基本上都被系统程序给占用了

常用端口

　　mysql：3306

　　oracle：1521

　　web：80

　　tomcat：8080

　　QQ：4000

　　feiQ：2425

网络编程三要素协议：

为计算机网络中进行数据交换而建立的规则、标准或约定的集合

UDP

　　面向无连接，数据不安全，速度快，不区分客户端与服务端

TCP

　　面向连接（三次握手），数据安全，速度略低。分为客户端和服务端

　　三次握手：客户端先想服务端发起请求，服务端响应请求，传输数据

UDP传输优化：

接收端Receive

import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class Demo1_Receive {

    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(6666);                            //创建socket相当于创建码头
        DatagramPacket packet = new DatagramPacket(new byte[1024], 1024);            //创建Packet相当于创建集装箱
        
        while(true){
            socket.receive(packet);                                                 //接货，接收数据
            
            byte[] arr = packet.getData();                                            //获取数据
            int len = packet.getLength();                                            //获取有效的字节个数
            String ip = packet.getAddress().getHostAddress();                        //获取IP地址
            int port = packet.getPort();                                            //获取端口号
            System.out.println(ip + ":" + new String(arr,0,len));
        }
    }

}

发送端Send

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.Scanner;

public class Demo1_Send {

    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);            //创建键盘录入对象
        DatagramSocket socket = new DatagramSocket();    //创建socket相当于创建码头
        
        while(true){
            String line = sc.nextLine();                //获取键盘录入的字符串
            if ("quit".equals(line)) {
                break;
            }
            DatagramPacket packet =                     //创建packet相当于集装箱
                    new DatagramPacket(line.getBytes(), line.getBytes().length,InetAddress.getByName("127.0.0.1"),6666);
            socket.send(packet);
        }
        socket.close();
    }

}

UDP传输多线程：

发送和接收在一个窗口完成

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Demo2 {

    public static void main(String[] args) {
        new Receive().start();
        
        new Send().start();
    }

}
class Receive extends Thread{
    @Override
    public void run() {
        try {
            DatagramSocket socket = new DatagramSocket(6666);                            //创建socket相当于创建码头
            DatagramPacket packet = new DatagramPacket(new byte[1024], 1024);            //创建Packet相当于创建集装箱
            
            while(true){
                socket.receive(packet);                                                 //接货，接收数据
                
                byte[] arr = packet.getData();                                            //获取数据
                int len = packet.getLength();                                            //获取有效的字节个数
                String ip = packet.getAddress().getHostAddress();                        //获取IP地址
                int port = packet.getPort();                                            //获取端口号
                System.out.println(ip + ":" + new String(arr,0,len));
            }
        } catch (SocketException e) {
            
            e.printStackTrace();
        } catch (IOException e) {
            
            e.printStackTrace();
        }
    }
}
class Send extends Thread{
    @Override
    public void run() {
        try {
            Scanner sc = new Scanner(System.in);            //创建键盘录入对象
            DatagramSocket socket = new DatagramSocket();    //创建socket相当于创建码头
            
            while(true){
                String line = sc.nextLine();                //获取键盘录入的字符串
                if ("quit".equals(line)) {
                    break;
                }
                DatagramPacket packet =                     //创建packet相当于集装箱
                        new DatagramPacket(line.getBytes(), line.getBytes().length,InetAddress.getByName("127.0.0.1"),6666);
                socket.send(packet);
            }
            socket.close();
        } catch (SocketException e) {
            
            e.printStackTrace();
        } catch (UnknownHostException e) {
            
            e.printStackTrace();
        } catch (IOException e) {
            
            e.printStackTrace();
        }
    }
}

UDP聊天图形化界面：

import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.Font;
import java.awt.Frame;
import java.awt.Panel;
import java.awt.TextArea;
import java.awt.TextField;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class Demo3_GUIChat extends Frame {
    
    public Demo3_GUIChat(){
        init();
        southPanel();
        centerPanel();
        event();
    }

    private void event() {
        this.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
    }

    private void centerPanel() {
        Panel center = new Panel();                //创建中间的Panel
        TextArea viewText = new TextArea();        //显示的文本区域
        TextArea sendText = new TextArea(5,1);        //发送的文本区域
        center.setLayout(new BorderLayout());     //设置为边界布局管理器
        center.add(sendText, BorderLayout.SOUTH);//发送的文本区域放在南边
        center.add(viewText, BorderLayout.CENTER);//显示区域放在中间
        viewText.setEditable(false);                 //设置为不可编辑
        viewText.setBackground(Color.WHITE);        //这只背景颜色
        sendText.setFont(new Font("hhh",Font.PLAIN ,16 ));    
        viewText.setFont(new Font("hhh",Font.PLAIN ,16 ));    
        this.add(center,BorderLayout.CENTER);
        
    }

    public void southPanel() {
        Panel south = new Panel();                //创建南边的Panel
        TextField tf = new TextField(15);            //创建文本字段存储IP地址
        Button send = new Button("发送");            //创建发送按钮
        Button log = new Button("记录");            //创建记录按钮
        Button clear = new Button("清屏");        //创建清屏按钮
        Button shake = new Button("震动");        //创建震动按钮
        south.add(tf);
        south.add(send);
        south.add(log);
        south.add(clear);
        south.add(shake);
        this.add(south,BorderLayout.SOUTH);        //将Panel放在Frame的南边
        
    }

    public void init() {
        this.setLocation(500,50);
        this.setSize(400, 600);
        this.setVisible(true);
    }

    public static void main(String[] args) {
        new Demo3_GUIChat();
    }

}

UDP聊天发送功能

UDP聊天记录功能

UDP聊天清屏功能

UDP聊天振动功能

UDP聊天快捷键和代码优化

UDP聊天生成jar文件

import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.Font;
import java.awt.Frame;
import java.awt.Panel;
import java.awt.TextArea;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Demo3_GUIChat extends Frame {
    
    private TextField tf;
    private Button send;
    private Button log;
    private Button clear;
    private Button shake;
    private TextArea viewText;
    private TextArea sendText;
    private DatagramSocket socket;
    private BufferedWriter bw;

    public Demo3_GUIChat(){
        init();
        southPanel();
        centerPanel();
        event();
    }

    private void event() {
        this.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                try {
                    socket.close();
                    bw.close();
                } catch (IOException e1) {
                    
                    e1.printStackTrace();
                }
                System.exit(0);
            }
        });
        send.addActionListener(new ActionListener() {
            
            @Override
            public void actionPerformed(ActionEvent e) {
                try {
                    send();
                } catch (IOException e1) {
                    
                    e1.printStackTrace();
                }
            }

        });
        log.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                try {
                    logFile();
                } catch (IOException e) {
                    
                    e.printStackTrace();
                }
            }

        });
        clear.addActionListener(new ActionListener() {
            
            @Override
            public void actionPerformed(ActionEvent e) {
                viewText.setText("");
            }
        });
        shake.addActionListener(new ActionListener() {
            
            @Override
            public void actionPerformed(ActionEvent e) {
                try {
                    send(new byte[]{-1},tf.getText());
                } catch (IOException e1) {
                    
                    e1.printStackTrace();
                }
            }

        });
        sendText.addKeyListener(new KeyAdapter() {
            @Override
            public void keyReleased(KeyEvent e) {
                //if (e.getKeyCode() == KeyEvent.VK_ENTER && e.isControlDown()) {    //isControlDown Ctrl键是否被按下
                if (e.getKeyCode() == KeyEvent.VK_ENTER) {
                    try {
                        send();
                    } catch (IOException e1) {
                        
                        e1.printStackTrace();
                    }
                }
            }
        });
    }
    private void shake() {
        int x = this.getLocation().x;                //获取横坐标位置
        int y = this.getLocation().y;                //获取纵坐标位置
        for(int i = 0; i < 10; i++){
        try {
            this.setLocation(x + 10,y + 10);
            Thread.sleep(10);
            this.setLocation(x + 10,y - 10);
            Thread.sleep(10);
            this.setLocation(x + 10,y - 10);
            Thread.sleep(10);
            this.setLocation(x - 10,y - 10);
            Thread.sleep(10);
            this.setLocation(x,y);
        } catch (InterruptedException e) {
            
            e.printStackTrace();
        }
        }
    }

    private void logFile() throws IOException {
        bw.flush();                             //刷新缓冲区
        FileInputStream fis = new FileInputStream("config.txt");
        ByteArrayOutputStream baos = new ByteArrayOutputStream();        //在内存中创建缓冲区
        
        int len;
        byte[] arr = new byte[8192];
        while((len = fis.read(arr)) != -1){
            baos.write(arr,0,len);
        }
        
        String str = baos.toString();                    //将内存中的内容转换成了字符串
        viewText.setText(str);
        
        fis.close();
    }
    private void send(byte[] arr,String ip) throws IOException{

        DatagramPacket packet =
                new DatagramPacket(arr,arr.length,InetAddress.getByName(ip),9999);
        socket.send(packet);         //发送数据
    }
    private void send() throws IOException {
        String message = sendText.getText();    //获取发送区域的内容
        String ip = tf.getText();                //获取IP地址
        ip = ip.trim().length() == 0 ? "255.255.255.255" : ip;
        
        send(message.getBytes(),ip);
        
        String time = getCurrentTime();                //获取当前时间
        String str = time + " 我对" + (ip.equals("255.255.255.255") ? "所有人" : ip) + "说
" +message + "

";
        viewText.append(str);                     //将信息添加到显示区域中
        bw.write(str);                            //将数据写到数据库中
        sendText.setText("");
        
    }
    private String getCurrentTime() {
        Date d = new Date();            //创建当前日期对象
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
        return sdf.format(d);            //将时间格式化
    }

    private void centerPanel() {
        Panel center = new Panel();                //创建中间的Panel
        viewText = new TextArea();
        sendText = new TextArea(5,1);
        center.setLayout(new BorderLayout());     //设置为边界布局管理器
        center.add(sendText, BorderLayout.SOUTH);//发送的文本区域放在南边
        center.add(viewText, BorderLayout.CENTER);//显示区域放在中间
        viewText.setEditable(false);                 //设置为不可编辑
        viewText.setBackground(Color.WHITE);        //这只背景颜色
        sendText.setFont(new Font("hhh",Font.PLAIN ,20 ));    
        viewText.setFont(new Font("hhh",Font.PLAIN ,20 ));    
        this.add(center,BorderLayout.CENTER);
        
    }

    public void southPanel() {
        Panel south = new Panel();                //创建南边的Panel
        tf = new TextField(15);
        tf.setText("127.0.0.1");
        send = new Button("发送");
        log = new Button("记录");
        clear = new Button("清屏");
        shake = new Button("震动");
        south.add(tf);
        south.add(send);
        south.add(log);
        south.add(clear);
        south.add(shake);
        this.add(south,BorderLayout.SOUTH);        //将Panel放在Frame的南边
        
    }

    public void init(){
        this.setLocation(500,50);
        this.setSize(600, 800);
        new Receive().start();
        try {
            socket = new DatagramSocket();
            bw = new BufferedWriter(new FileWriter("config.txt",true));        //需要在尾部追加
        } catch (Exception e) {
            
            e.printStackTrace();
        }
        this.setVisible(true);
    }
    private class Receive extends Thread {        //接收和发送需要同时执行，所以定义成多线程的
        @Override
        public void run() {
            try {
                DatagramSocket socket = new DatagramSocket(9999);
                DatagramPacket packet = new DatagramPacket(new byte[8192], 8192);
                while(true){
                socket.receive(packet);         //接收信息
                byte[] arr = packet.getData();    //获取字节数据
                int len = packet.getLength();    //获取有效的字节数据
                if (arr[0] == -1 && len == 1) {    //如果发过来的数组第一个存储的值是-1，并且数组长度是1
                    shake();                    //调用震动方法
                    continue;                    //终止本次循环，继续下次循环，因为震动后不需要执行下面的代码
                }
                String message = new String(arr, 0, len);    //转换成字符串
                
                String time = getCurrentTime();        //获取当前时间
                String ip = packet.getAddress().getHostAddress();    //获取ip地址
                String str = time + " " + ip + "对我说：
" + message + "

";
                viewText.append(str);
                bw.write(str);
                }
            } catch (Exception e) {
                
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        new Demo3_GUIChat();
    }

}

TCP协议：

1、客户端

创建Socket连接服务端（指定ip地址，端口号）通过ip地址找对应的服务器

调用Socket的getInputStream（）和getOutputStream（）方法获取和服务端相连的IO流

输入流可以读取服务端输出流写出的数据

输出流可以写出数据到服务端的输入流

package com.tcp;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.net.UnknownHostException;

public class Demo1_Client {

    public static void main(String[] args) throws UnknownHostException, IOException {
        Socket socket = new Socket("127.0.0.1", 12345);
        
        InputStream is = socket.getInputStream();        //获取客户端输入流
        OutputStream os = socket.getOutputStream();        //获取客户端的输出流
        
        byte[] arr = new byte[1024];                    
        int len = is.read(arr);                            //读取服务器发过来的数据
        System.out.println(new String(arr,0,len));         //将数据转换成字符串并打印
        
        os.write("我爱学习".getBytes());                    //客户端向服务器写数据
        
        socket.close();
    }

}

2、服务端

创建ServerSocket（需要指定端口号）

调用ServerSocket的accept（）方法接收一个客户端请求，得到一个Socket

调用Socket的getInputStream（）和getOutputStream（）方法获取和客户端相连的IO流

输入流可以读取客户端输出流写出的数据

输出流可以写出数据到客户端的输入流

package com.tcp;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Demo1_Server {

    public static void main(String[] args) throws IOException {
        ServerSocket server = new ServerSocket(12345);
        
        Socket socket = server.accept();                //接受客户端的请求
        InputStream is = socket.getInputStream();        //获取客户端输入流
        OutputStream os = socket.getOutputStream();        //获取客户端的输出流
        
        os.write("学习爱我".getBytes());                    //服务器向客户端写数据
        
        byte[] arr = new byte[1024];                    
        int len = is.read(arr);                            //读取客户端发过来的数据
        System.out.println(new String(arr,0,len));         //将数据转换成字符串并打印
        
        socket.close();
    }

}

TCP协议代码优化：

package com.tcp;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.Socket;
import java.net.UnknownHostException;

public class Demo2_Client {

    public static void main(String[] args) throws UnknownHostException, IOException {
        Socket socket = new Socket("127.0.0.1", 12345);
        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));        //将字节流包装成了字符流
        PrintStream ps = new PrintStream(socket.getOutputStream());                //PrintStream中有写出换行的方法
        
        System.out.println(br.readLine());
        ps.println("我爱学习");
        System.out.println(br.readLine());
        ps.println("好好学习，天天向上");
        socket.close();
    }

}

package com.tcp;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Demo2_Server {

    public static void main(String[] args) throws IOException {
        ServerSocket server = new ServerSocket(12345);
        
        Socket socket = server.accept();                //接受客户端的请求
        
        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));        //将字节流包装成了字符流
        PrintStream ps = new PrintStream(socket.getOutputStream());                //PrintStream中有写出换行的方法
        
        ps.println("你爱学习吗？");
        System.out.println(br.readLine());
        ps.println("真的吗？");
        System.out.println(br.readLine());
        socket.close();
    }

}

服务端是多线程的：

public static void demo2() throws IOException {
        ServerSocket server = new ServerSocket(12345);

        Socket socket = server.accept();             // 接受客户端的请求
        new Thread(){
            public void run() {
                try {
                    BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream())); // 将字节流包装成了字符流
                    PrintStream ps = new PrintStream(socket.getOutputStream()); // PrintStream中有写出换行的方法

                    ps.println("你爱学习吗？");
                    System.out.println(br.readLine());
                    ps.println("真的吗？");
                    System.out.println(br.readLine());
                    socket.close();
                } catch (IOException e) {
                    
                    e.printStackTrace();
                }
            };
        }.start();
    }

练习1：

客户端向服务端写字符串（键盘录入），服务端（多线程）将字符串反转后写会，客户端再次读取到时反转后的字符串

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Text1_Client {
    /**
     * 需求：客户端向服务端写字符串（键盘录入），服务端（多线程）将字符串反转后写会，客户端再次读取到时反转后的字符串
     * @throws IOException 
     * @throws UnknownHostException 
     */
    public static void main(String[] args) throws UnknownHostException, IOException {
        Scanner sc = new Scanner(System.in);
        Socket socket = new Socket("127.0.0.1", 54321);                            //创建客户端，指定IP地址和端口号
        
        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));        //获取输入流
        PrintStream ps = new PrintStream(socket.getOutputStream());        //获取输出流
        
        ps.println(sc.nextLine());                 //将字符串写到服务器去
        System.out.println(br.readLine());        //将反转后的结果读出来
        
        socket.close();
    }

}

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

public class Test1_Server {

    public static void main(String[] args) throws IOException {
        ServerSocket server = new ServerSocket(54321);
        System.out.println("服务器启动，绑定54321端口");
        
        while(true){
            Socket socket = server.accept();            //接受客户端的请求
            
            new Thread(){                                //开启一条线程                
                public void run() {
                    try {
                        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));        //获取输入流
                        PrintStream ps = new PrintStream(socket.getOutputStream());        //获取输出流
                        
                        String line = br.readLine();                    //将客户端写过来的数据读取出来
                        line = new StringBuilder(line).reverse().toString();    //链式编程
                        ps.println(line);                            //反转后写回去
                        
                        socket.close();
                    } catch (IOException e) {
                        
                        e.printStackTrace();
                    }
                };
            }.start();
        }
    }

}

练习2：

客户端向服务器上传文件

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Test2_UpdateClient {

    public static void main(String[] args) throws UnknownHostException, IOException {
        //1、提示输入要上传的文件路径，验证路径是否存在或是否是文件夹
                File file = getFile();
                //2、发送文件名到服务端
                Socket socket = new Socket("127.0.0.1",12345);
                BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                PrintStream ps = new PrintStream(socket.getOutputStream());
                ps.println(file.getName());
                //6、接收结果，如果存在给予提示，程序直接退出
                String result = br.readLine();            //读取存在后不存在的结果
                if ("存在".equals(result)) {
                    System.out.println("您上传的文件已存在，请不要重复上传");
                    socket.close();
                    return;
                }
                //7、如果不存在，定义FileInputStream读取文件,写出到网络
                FileInputStream fis = new FileInputStream(file);
                byte[] arr = new byte[8192];
                int len;
                
                while((len = fis.read(arr)) != -1) {
                    ps.write(arr,0,len);
                }
                
                fis.close();
                socket.close();
            }

            private static File getFile() {
                Scanner sc = new Scanner(System.in);
                System.out.println("请输入一个文件路径：");
                
                while (true) {
                    String line = sc.nextLine();
                    File file = new File(line);
                    
                    if (!file.exists()) {
                        System.out.println("您录入的文件路径不存在，请重新录入：");
                    }else if (file.isDirectory()) {
                        System.out.println("您录入的是文件夹路径，请重新录入一个文件路径：");
                    }else {
                        return file;
                    }
                }
            }

        }

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;


public class Test2_UpdateServer {

    public static void main(String[] args) throws IOException {
    //3、建立多线程的服务器
        ServerSocket server = new ServerSocket(12345);
        System.out.println("服务器启动，绑定12345端口...");
        
        //4、读取文件名
        while (true) {
            final Socket socket = server.accept();        //接受请求
            new Thread() {
                public void run() {
                    try {
                        InputStream is = socket.getInputStream();
                        BufferedReader br = new BufferedReader(new InputStreamReader(is));
                        PrintStream ps = new PrintStream(socket.getOutputStream());
                        String fileName = br.readLine();
                        
                        //5.判断文件是否存在, 将结果发回客户端
                        File dir = new File("update");
                        dir.mkdir();                                //创建文件夹
                        File file = new File(dir,fileName);            //封装成File对象
                        
                        if(file.exists()) {                            //如果服务器已经存在这个文件
                            ps.println("存在");                        //将存在写给客户端
                            socket.close();                            //关闭socket
                            return;
                        }else {
                            ps.println("不存在");
                        }
                        
                        //8.定义FileOutputStream, 从网络读取数据, 存储到本地
                        FileOutputStream fos = new FileOutputStream(file);
                        byte[] arr = new byte[8192];
                        int len;
                        
                        while((len = is.read(arr)) != -1) {
                            fos.write(arr, 0, len);
                        }
                        
                        fos.close();
                        socket.close();
                    } catch (IOException e) {
                        
                        e.printStackTrace();
                    }
                }
        
            }.start();
        }
    }
}