网络编程应用：基于UDP协议【实现文件下载】--练习

女爷i 2022-06-16 03:48 245阅读 0赞

要求：

基于UDP协议实现文件下载

**发送方–请求–接收方发送文件–发送方接收文件**

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**代码：**

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**发送方：**

package Homework1;
    
    import java.io.File;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.InetAddress;
    import java.net.SocketException;
    import java.net.UnknownHostException;
    
    public class Send {
        
        public static void main(String[] args){
            System.out.println("发送者启动");
    
    
            DatagramSocket socket=null;
            FileOutputStream fos=null;
            try {
                //1.发送请求
                socket=new DatagramSocket();
                String string="请求下载文件...";
                DatagramPacket packet=new DatagramPacket(string.getBytes(), string.getBytes().length, InetAddress.getLocalHost(), 6635);
                socket.send(packet);
    
                //2.创建file对象，以及文件输出流
                File file=new File("b.txt");
                fos=new FileOutputStream(file);
    
                //3.接收文件
                byte[] buf=new byte[1024];
                while(true){
                    DatagramPacket p=new DatagramPacket(buf, buf.length);
                    socket.receive(p);
                    String string2=new String(p.getData(), 0, p.getLength());
    
                    //4.根据接收方发来的数据，判断文件是否传输完毕
                    if(string2.equals("发送完毕")){
                        break;
                    }
                    fos.write(string2.getBytes());
                    fos.flush();
                }
    
            } catch (SocketException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (UnknownHostException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }finally {
                if(socket!=null){
                    socket.close();
                }
                if(fos!=null){
                    try {
                        fos.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
    
        }
    }

--------------------

接收方：

package Homework1;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.SocketException;
    
    public class Receive {
        public static void main(String[] args){
            System.out.println("接收者启动");
    
    
            DatagramSocket socket=null;
            FileInputStream fis=null;
            try {
                //1.创建Datagramsocket对象，相当于TCP中的Socket
                socket=new DatagramSocket(6635);
    
                //2.创建Datagrampacket对象，用于装数据
                byte[] buf=new byte[1024];
                DatagramPacket packet=new DatagramPacket(buf, buf.length);
                //3.接收数据，收到发送方请求“下载文件”
                socket.receive(packet);
                System.out.println(new String(packet.getData(),0,packet.getLength()));
    
                //4.发送文件给--发送方
                File file=new File("a.txt");//要给发送方的文件
                fis=new FileInputStream(file);
                byte[] b=new byte[10];
                int count=0;
                while((count=fis.read(b))!=-1){
                    DatagramPacket p=new DatagramPacket(b, count,packet.getAddress(),packet.getPort());
                    socket.send(p);
                }
    
                //5.文件发送完后，给--发送方回复一句话
                String string="发送完毕";
                packet=new DatagramPacket(string.getBytes(), string.getBytes().length,packet.getAddress(),packet.getPort());
                socket.send(packet);
            } catch (SocketException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }finally {
                if(socket!=null){
                    socket.close();
                }
                if(fis!=null){
                    try {
                        fis.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }   
        }
    }

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**运行结果：**  
**发送方：**

![这里写图片描述][SouthEast]

**接收方：**  
![这里写图片描述][SouthEast 1]

[SouthEast]: /images/20220616/f4a6972bf35346acbc658a2ddc98ab5c.png
[SouthEast 1]: /images/20220616/375894cd1d164273b45027df6a28782a.png