Java 网络编程--TCP

系统管理员 2021-05-03 15:45 604阅读 0赞

## 一. 简介 ##

*  需要建立连接，形成传输数据的通道
 *  通过三次握手完成连接，是可靠协议
 *  以字节流的方式发送大量数据

## 二. 通信过程 ##

![这里写图片描述][SouthEast]

**客户端：**  
1..创建客户端的socket服务，指定目的主机和端口  
2..为了发送数据，应该获取socket中的输出流  
3..获取socket中的输入流来获取服务端的反馈数据  
4..关闭资源

**服务端：**  
1..创建服务端的ServerSocket服务，并监听一个端口  
2..通过accept方法 等待并获取连接过来的客户端socket对象  
3..获取客户端发送过来的数据（使用客户端socket的输入流来读取数据）  
4..反馈数据到该客户端（使用客户端socket的输出流来写出数据）  
5..关闭资源

## 三. 应用 ##

**1..客户端并发登录，服务端处理并反馈**

/* * 客户端 */
    class Client{
    
        public static void main(String[] args) throws Exception {
            Socket s = new Socket(InetAddress.getLocalHost(),10000);   //客户端建立socket服务，指定目的主机和端口
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));  //源-读取键盘录入
            PrintWriter out = new PrintWriter(s.getOutputStream(),true);   //目的-socket输出流，包装成打印流
            BufferedReader bin = new BufferedReader(new InputStreamReader(s.getInputStream()));  //源-读取socket输入流
            int i =0;
            for(i =0 ;i<3 ;i++)
            {
                String line = br.readLine();  //键盘录入的信息
                if(line==null)
                    break;
                out.println(line);     //写入socket输出流
                String mess = bin.readLine();  //服务器反馈的信息
                if(mess.contains("欢迎"))
                {
                    System.out.println("Server Message:"+mess);
                    break;
                }
                System.out.println("Server Message:"+mess);
            }
            if(i>=3)
                System.out.println("错误次数太多");
            s.close();
            br.close();
        }
    }

/* *服务端 */
    class Server { 
    
        public static void main(String[] args) throws Exception {
            ServerSocket ss = new ServerSocket(10000);  //服务端建立ServerSocket服务，监听指定端口
            while(true)
            {
                Socket s = ss.accept();
                new Thread(new ServerThread(s)).start();  //进来一个用户，则开启一个线程
            }
        }
    }
    
    class ServerThread implements Runnable{ 
        private Socket s;
        ServerThread(Socket s){
            this.s = s;
        }
        public void run() {
            String ip = s.getInetAddress().getHostAddress();
            System.out.println(ip+"已连接");
            try{
                for(int i =0 ;i<3;i++)
                {
                    BufferedReader bfr = new BufferedReader(new FileReader("E:\\user.txt")); //源-服务端数据文件或数据库,包装成BufferedReader
                    BufferedReader bin = new BufferedReader(new InputStreamReader(s.getInputStream())); //源-客户端提交的数据
                    PrintWriter out = new PrintWriter(s.getOutputStream(),true);  //目的-socket输出流，包装成打印流
                    String name = bin.readLine();
                    String line = null;
                    boolean flag = false;
                    while((line = bfr.readLine())!=null)
                    {
                        if(line.equals(name))
                        {
                            flag = true;
                            break;
                        }
                    }
                    if(flag == true)
                    {
                        System.out.println(name+"已登录");
                        out.println("欢迎"+name);   //将信息反馈给客户端
                    }
                    else
                        out.println("用户名不存在");
                }
                s.close();
            }catch(Exception e){
                throw new RuntimeException(ip+"校验失败");
            }
        }
    }

**2..客户端并发上传图片，服务端接收并反馈**

/* * 客户端 */
    class UploadClient {
    
        public static void main(String[] args) throws Exception {
            Socket s = new Socket(InetAddress.getLocalHost(),9999);
            BufferedOutputStream bout = new BufferedOutputStream(s.getOutputStream()); //目的-socket输出流
    
            FileInputStream fin = new FileInputStream("E:\\晴天.mp3");  //读文件并写入socket输出流
            int len = 0;
            while((len = fin.read())!=-1)
            {
                bout.write(len);
            }
            s.shutdownOutput();  //写完..结束标记
    
            BufferedReader bin = new BufferedReader(new InputStreamReader(s.getInputStream()));  //源-读取socket输入流
            String mess = bin.readLine();  //服务器反馈的信息
            System.out.println(mess);
    
            s.close();
            fin.close();
        }
    }

/*
    *    服务端
    * /
    class UploadServer{
        public static void main(String[] args) throws Exception {
            ServerSocket ss = new ServerSocket(9999);
            while(true)
            {
                Socket s = ss.accept();
                new Thread(new UploadThread(s)).start();
            }
        }
    }
    class UploadThread implements Runnable {
        private Socket s = null;
        UploadThread(Socket s)
        {
            this.s = s;
        }
        public void run(){
            String ip = s.getInetAddress().getHostAddress();
            try {
                System.out.println(ip+"已连接");
    
                int time = (int) System.currentTimeMillis();
                BufferedInputStream bin = new BufferedInputStream(s.getInputStream()); //源-socket输入流，客户端发来的数据
                FileOutputStream fi = new FileOutputStream("F:\\"+time+".mp3");  //目的-磁盘，将客户端发来的文件写入本地
                int len;
                while((len=bin.read())!=-1)
                {
                    fi.write(len);
                }
    
                PrintWriter out = new PrintWriter(s.getOutputStream(),true);  //目的-socket输出流，包装成打印流
                out.println("上传成功");  //反馈给客户端
    
                fi.close();
                s.close();
            } catch (Exception e) {
                throw new RuntimeException(ip+"上传失败");
            }
        }
    }

[SouthEast]: /images/20210502/ee79d18259ff4f5f9dd3e02b919208b7.png