重温Java网络编程（实现简易TCP，UDP应用）

短命女 2022-01-15 13:37 171阅读 0赞

> 关于TCP以及UDP的相关知识，在此就不做相关总结，如有需要可以参考https://blog.csdn.net/li\_ning\_/article/details/52117463

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### 一、使用TCP实现一个简易登录功能 ###

#### 1.创建一个实体类 User.java ####

package com.tcp.multithreadingTcp;
    
    import java.io.Serializable;
    
    public class User implements Serializable { 
        private String username;
        private String password;
    
        public String getUsername() { 
            return username;
        }
    
        public void setUsername(String username) { 
            this.username = username;
        }
    
        public String getPassword() { 
            return password;
        }
    
        public void setPassword(String password) { 
            this.password = password;
        }
    
        @Override
        public String toString() { 
            return "User{" +
                    "username='" + username + '\'' +
                    ", password='" + password + '\'' +
                    '}';
        }
    }

#### 2.服务器端代码 LoginServer.java ####

package com.tcp.multithreadingTcp;
    
    import java.io.*;
    import java.net.ServerSocket;
    import java.net.Socket;
    
    public class LoginServer { 
        public static void main(String[] args) throws IOException { 
            //创建一个ServerSocket，指定监听的端口
            ServerSocket serverSocket = new ServerSocket(8888);
    
            int i = 0;
            while (true) { 
                //使用ServerSocket监听用户请求
                Socket socket = serverSocket.accept();//如果没有请求则阻塞
                //启动一个登录线程
                new Thread(new LoginThread(socket)).start();
    
                System.out.println("你是访问该服务器的第" + ++i + "个用户,你的ip地址为"
                        + socket.getInetAddress().getHostAddress());
                socket.close();
            }
        }
    }

#### 3.登录线程代码 LoginThread.java ####

package com.tcp.multithreadingTcp;
    
    import java.io.*;
    import java.net.Socket;
    
    public class LoginThread implements Runnable { 
        private Socket socket;
    
        LoginThread(Socket socket) { 
            this.socket = socket;
        }
    
        //处理用户请求
        @Override
        public void run() { 
            //接收来自客户端的数据并输出
            try { 
                ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream());
                User user = (User) objectInputStream.readObject();
                System.out.println(user.toString());
    
                //发送反馈
                DataOutputStream dataOutputStream = new DataOutputStream(socket.getOutputStream());
                if ("zhangsan".equals(user.getUsername()) && "1234".equals(user.getPassword())) { 
                    dataOutputStream.writeUTF("登录成功");
                } else { 
                    dataOutputStream.writeUTF("登录失败");
                }
    
                //关闭资源
                dataOutputStream.close();
                objectInputStream.close();
            } catch (IOException | ClassNotFoundException e) { 
                e.printStackTrace();
            }
        }
    }

#### 4.客户端代码 LoginClient.java ####

package com.tcp.multithreadingTcp;
    
    import java.io.*;
    import java.net.InetAddress;
    import java.net.Socket;
    import java.util.Scanner;
    
    public class LoginClient { 
        public static void main(String[] args) throws IOException { 
            //创建一个Socket，指定服务器端的ip与端口
            Socket socket = new Socket(InetAddress.getLocalHost(), 8888);
    
            Scanner sc = new Scanner(System.in);
            System.out.print("请输入用户名:");
            String username = sc.nextLine();
            System.out.print("请输入密码:");
            String password = sc.nextLine();
            User user = new User();
            user.setUsername(username);
            user.setPassword(password);
    
            //发送登录信息
            OutputStream outputStream = socket.getOutputStream();
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);
            objectOutputStream.writeObject(user);
    
            //接收数据
            InputStream inputStream = socket.getInputStream();
            DataInputStream dataInputStream = new DataInputStream(inputStream);
            String res = dataInputStream.readUTF();
            System.out.println(res);
    
            //关闭资源
            dataInputStream.close();
            inputStream.close();
            objectOutputStream.close();
            outputStream.close();
            socket.close();
        }
    }

> 运行结果:(客户端)

请输入用户名:zhangsan
    请输入密码:1234
    登录成功

> 运行结果:(服务端)

User{username='zhangsan', password='1234'}
    你是访问该服务器的第1个用户,你的ip地址为xxx.xxx.xxx.xxx

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

### 二、使用UDP实现一个简易聊天室功能 ###

> UDP相较于TCP实现简单一些，所以代码量也稍微的少一些

#### 1.服务端代码 ####

package com.udp.moreThanOneUdp;
    
    import java.io.IOException;
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.InetAddress;
    import java.util.Scanner;
    
    /** * 功能:在线客服. * 技能:使用UDP网络编程完成 * 注意 * 1. UDP编程中客户端和服务器端区分不明显,双方代码差别不大 * 2.主动发起请求的一段是客户端，接收请求的是服务器端;一旦通信开始，客户端和服务器端无差别 * 3.不涉及IO流 * 4.主要API * - DatagramSocket:socket,作用是发送和接收DatagramPacket * - DatagramPacket:数据报（封装数据，目的地址，源地址，端口号） */
    public class AskServer { 
        public static void main(String[] args) throws IOException { 
            //创建一个DatagramSocket,用来发送和接收数据
            DatagramSocket socket = new DatagramSocket(8888);//服务器端接收数据的端口
            Scanner sc = new Scanner(System.in);
            while (true) { 
                //使用DatagramSocket接收一个DatagramPacket
                byte[] buf = new byte[1024];
                DatagramPacket datagramPacket1 = new DatagramPacket(buf, buf.length);
                socket.receive(datagramPacket1);
                System.out.println("对方说:" + new String(datagramPacket1.getData(), 0, datagramPacket1.getLength()));
    
                //使用DatagramSocket发送一个DatagramPacket
                System.out.print("请您输入:");
                String info = sc.nextLine();
                InetAddress inetAddress = datagramPacket1.getAddress();
                int port = datagramPacket1.getPort();
                DatagramPacket datagramPacket2 = new DatagramPacket(info.getBytes(), info.getBytes().length, inetAddress, port);
                socket.send(datagramPacket2);
                if (info.equals("bye")) { 
                    break;
                }
            }
            System.out.println("聊天结束");
    
            //关闭资源
            socket.close();
        }
    }

#### 2.客户端代码 ####

package com.udp.moreThanOneUdp;
    
    import java.io.IOException;
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.InetAddress;
    import java.util.Scanner;
    
    public class AskClient { 
        public static void main(String[] args) throws IOException { 
            //创建一个DatagramSocket,用来发送和接收数据
            DatagramSocket socket = new DatagramSocket(8889);//客户端接收数据的端口,可以省略，会自动分配
            Scanner sc = new Scanner(System.in);
            while (true) { 
                //使用DatagramSocket发送一个DatagramPacket
                System.out.print("请您输入:");
                String info = sc.nextLine();
                InetAddress inetAddress = InetAddress.getLocalHost();
                DatagramPacket datagramPacket1 = new DatagramPacket(info.getBytes(), info.getBytes().length, inetAddress, 8888);
                socket.send(datagramPacket1);
                if (info.equals("bye")) { 
                    break;
                }
    
                //使用DatagramSocket接收一个DatagramPacket
                byte[] buf = new byte[1000];
                DatagramPacket datagramPacket2 = new DatagramPacket(buf, buf.length);
                socket.receive(datagramPacket2);
                System.out.println("对方说:" + new String(buf, 0, datagramPacket2.getLength()));
            }
            System.out.println("聊天结束");
    
            //关闭资源
            socket.close();
        }
    }

> 运行结果:(客户端)

请您输入:你好呀
    对方说:你是谁
    请您输入:我是张三，你呢
    对方说:我是李四
    请您输入:好的，我要忙了
    对方说:bye
    请您输入:bye
    聊天结束

> 运行结果:(服务端)

对方说:你好呀
    请您输入:你是谁
    对方说:我是张三，你呢
    请您输入:我是李四
    对方说:好的，我要忙了
    请您输入:bye
    聊天结束

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

### 三、使用TCP实现文件上传以及文件下载功能 ###

>  *  文件上传的本质:文件从客户端到服务器端的复制
>  *  文件下载的本质:文件从服务器端到客户端的复制
>  *  文件的上传和下载都是两次文件复制

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

#### 1.文件上传功能服务端代码 ####

package com.tcp.uploadTcp;
    
    import java.io.*;
    import java.net.ServerSocket;
    import java.net.Socket;
    
    public class UploadServer { 
        public static void main(String[] args) throws IOException { 
            ServerSocket serverSocket = new ServerSocket(8888);
            Socket socket = serverSocket.accept();
    
            //创建一个输入流和一个输出流
            BufferedInputStream bufferedInputStream = new BufferedInputStream(socket.getInputStream());
            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(new File("/test1.txt")));
    
            //使用输入流和输出流完成文件复制
            //中转站
            int n;
    
            //读取末尾的一个字节的内容赋给n
            n = bufferedInputStream.read();
            while (n != -1){ 
                //写一个字节
                bufferedOutputStream.write(n);
                System.out.println(1);
                //读一个字节
                n = bufferedInputStream.read();
            }
    
            //关闭资源
            bufferedInputStream.close();
            bufferedOutputStream.close();
            socket.close();
            serverSocket.close();
        }
    }

#### 2.文件上传功能客户端代码 ####

package com.tcp.uploadTcp;
    
    import java.io.*;
    import java.net.InetAddress;
    import java.net.ServerSocket;
    import java.net.Socket;
    import java.net.UnknownHostException;
    
    public class UploadClient { 
        public static void main(String[] args) throws IOException { 
            Socket socket = new Socket(InetAddress.getLocalHost(),8888);
    
            //创建一个输入流和一个输出流
            BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(new File("/test.txt")));
            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(socket.getOutputStream());
    
            //关闭资源
            bufferedInputStream.close();
            bufferedOutputStream.close();
            socket.close();
        }
    }

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

#### 1.文件下载功能服务端代码 ####

package com.tcp.downloadTcp;
    
    import java.io.*;
    import java.net.ServerSocket;
    import java.net.Socket;
    
    public class DownloadServer { 
        public static void main(String[] args) throws IOException { 
            ServerSocket serverSocket = new ServerSocket(8888);
            Socket socket = serverSocket.accept();
    
            //创建一个输入流和一个输出流
            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(new File("/test.txt")));
            BufferedInputStream bufferedInputStream = new BufferedInputStream(socket.getInputStream());
    
            //使用输入流和输出流完成文件复制
            //中转站
            int n;
    
            //读取末尾的一个字节的内容赋给n
            n = bufferedInputStream.read();
            while (n != -1){ 
                //写一个字节
                bufferedOutputStream.write(n);
    
                //读一个字节
                n = bufferedInputStream.read();
            }
    
            //关闭资源
            bufferedInputStream.close();
            bufferedOutputStream.close();
            socket.close();
            serverSocket.close();
        }
    }

#### 2.文件下载功能客户端代码 ####

package com.tcp.downloadTcp;
    
    import java.io.*;
    import java.net.InetAddress;
    import java.net.Socket;
    
    public class DownloadClient { 
        public static void main(String[] args) throws IOException { 
            Socket socket = new Socket(InetAddress.getLocalHost(),8888);
    
            //创建一个输入流和一个输出流
            BufferedInputStream bufferedInputStream = new BufferedInputStream(socket.getInputStream());
            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(new File("/test1.txt")));
    
            //关闭资源
            bufferedInputStream.close();
            bufferedOutputStream.close();
            socket.close();
        }
    }

> 其实上传功能和下载功能的逻辑是相同的，只不过一个是文件c => s,一个是文件s => c

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> 参考视频：[https://www.bilibili.com/video/av31123719/][https_www.bilibili.com_video_av31123719]

[https_www.bilibili.com_video_av31123719]: https://www.bilibili.com/video/av31123719/