2020-07-14TCP

TCP通信原理

TCP协议是一种可靠的网络协议，它在通信的两端各建立一个Socket对象，从而在通信的两端形成网络虚拟链路，一旦建立虚拟的网络通信，程序的两端就可以通过虚拟链路进行通信。
java对基于TCP协议的网络提供了良好的封装，使用Socket对象来代表两端的通信端口，并通过Socket产生IO流来进行网络通信。
JAVA为客户提供Socket类，为服务器端提供ServerSocket类

TCP发送数据

• 步骤
  ①创建客户端的Socket对象(Socket(String host,int port))
  ②获取输出流，写数据(OutputStream getOutputStream())
  ③释放资源
  void close()

public class TCPSend {
    public static void main(String[] args) throws IOException {
        //创建客户端的Socket对象（Socket）
        Socket socket = new Socket(InetAddress.getByName("DESKTOP-0NL0JDK"),10086);
        // Socket socket = new Socket("DESKTOP-0NL0JDK",10086);
        //获得输出流，写数据
        OutputStream outputStream = socket.getOutputStream();
        outputStream.write("hello,tcp".getBytes());
        //释放资源
        outputStream.close();
    }
}

TCP接收数据

①创建服务器端的socket对象（ServerSocket(int port)）
②获取客户端连接，返回一个Socket对象(Socket accept())
③获取输入流，读数据，并把数据显示在控制台(InputStream getInputStream())
④释放资源(void close())

   public static void main(String[] args) throws IOException {
        //创建服务器端的Socket对象
        //ServerSocket(int port)创建绑定指定端口的服务器套接字
        ServerSocket serverSocket = new ServerSocket(10086);
        //Socket accept()倾听要链接到此套接字并接受它
        Socket socket = serverSocket.accept();
        //获取输入流，读数据，并把数据显示在控制台‘
        InputStream inputStream = socket.getInputStream();
        byte[] bytes = new byte[1024];
        int len  = inputStream.read(bytes);
        String data = new String(bytes,0,len);
        System.out.println("数据是："+data);
        serverSocket.close();
        socket.close();
    }

带有反馈和接收反馈的客户端和服务端

public class Send {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket(InetAddress.getByName("DESKTOP-0NL0JDK"), 10000);
        OutputStream outputStream = socket.getOutputStream();
        outputStream.write("hello".getBytes());
        //接收服务器的反馈
        InputStream inputStream = socket.getInputStream();
        byte[] bytes = new byte[1024];
        int len = inputStream.read(bytes);
        String s = new String(bytes,0,len);
        System.out.println("服务端"+s);
        socket.close();
    }
}

public class Receive {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(10000);
        Socket s = serverSocket.accept();
        InputStream inputStream = s.getInputStream();
        byte[] bytes = new byte[1024];
        int len = inputStream.read(bytes);
        String str = new String(bytes,0,len);
        System.out.println("客户端发送来的数据为"+str);
        //向客户端发送反馈信息
        OutputStream outputStream = s.getOutputStream();
        outputStream.write("服务器接收到数据".getBytes());
        serverSocket.close();
    }
}

练习

• 客户端：数据来自文本文件，接收服务器反馈
• 服务器：接收到的数据写入文本文件，给出反馈
• 出现问题：程序一直等待
• 原因：读数据的方法是阻塞式的
• 解决办法：
  ①自定义结束标记
  ②使用shutdownOutput()方法

public class Send {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket(InetAddress.getByName("DESKTOP-0NL0JDK"), 10000);
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
        BufferedReader bufferedReader = new BufferedReader(new FileReader("Test\\zzt.txt"));
        String line;
        while((line=bufferedReader.readLine())!=null){
            bufferedWriter.write(line);
            bufferedWriter.newLine();
            bufferedWriter.flush();
        }
        socket.shutdownOutput();
        //接收服务器反馈
        BufferedReader bufferedReader1 = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        String line1 = bufferedReader1.readLine();
        System.out.println(line1);
        socket.close();
    }
}


public class Receiver {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(10000);
        Socket accept = serverSocket.accept();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(accept.getInputStream()));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("Test\\zzt3.txt"));
        String line;
        while ((line = bufferedReader.readLine()) != null) {
            bufferedWriter.write(line);
            bufferedWriter.newLine();
            bufferedWriter.flush();
        }

        BufferedWriter bufferedWriter1 = new BufferedWriter(new OutputStreamWriter(accept.getOutputStream()));
        bufferedWriter1.write("文件上传成功！");
        bufferedWriter1.newLine();
        bufferedWriter1.flush();
        serverSocket.close();
    }
}