【网络编程】三、Socket 和 ServerSocket

一、Socket

在客户/服务器通信模式中，客户端需要主动创建与服务器连接的Socket。服务器端收到客户的链接请求，也会创建与客户连接的Socket.

Socket可以看作是通信连接两端的数据收发器。服务器与客户都通过套接字来收发数据。

二、ServerSocket

在客户/服务器通信模式中，服务器端需要创建监听特定的端口的ServerSocket.ServerSocket服务接收客户端的链接请求。

三、服务器和客户端代码示意

3.1、客户端代码

package com.study.sxf.common.web.socket.io.step1;

import java.io.*;
import java.net.Socket;

/**
 * @Date 2022/3/12 2:25 PM
 **/
public class EchoClient {

    private static Integer serverPort = 8080;
    private static String serverIp = "127.0.0.1";


    public static void main(String[] args) throws IOException {
        EchoClient echoClient = new EchoClient();
        //step1:建立连接
        Socket socket = echoClient.buildSocket();
        System.out.println("客户端连接建立成功");


        //step2:发送请求
        PrintWriter printWriter = echoClient.getPrintWriter(socket);
        String req = "我是小明";
        System.out.println("客户端发送请求=>" + req);
        printWriter.println(req);
        socket.shutdownOutput();

        //step3:接收响应
        BufferedReader bufferedReader = echoClient.getReader(socket);
        String resp = echoClient.readResponse(bufferedReader);
        System.out.println("客户单接收响应=>" + resp);

        //step4:关闭客户端连接
        System.out.println("客户端关闭连接");
        socket.close();

    }

    /**
     * 建立连接
     *
     * @return
     * @throws IOException
     */
    private Socket buildSocket() throws IOException {
        return new Socket(serverIp, serverPort);
    }

    /**
     * 建立发送请求的管道
     *
     * @param socket
     * @return
     * @throws IOException
     */
    private PrintWriter getPrintWriter(Socket socket) throws IOException {
        return new PrintWriter(socket.getOutputStream(),true);
    }

    /**
     * 建立接收响应的管道
     *
     * @param socket
     * @return
     * @throws IOException
     */
    private BufferedReader getReader(Socket socket) throws IOException {
        return new BufferedReader(new InputStreamReader(socket.getInputStream()));
    }

    /**
     * 读取响应
     * @param bufferedReader
     * @return
     * @throws IOException
     */
    private String readResponse(BufferedReader bufferedReader) throws IOException {
        StringBuffer resp = new StringBuffer();
        String msg= null;
//        String msg = bufferedReader.readLine();
//        return msg;
        while ((msg = bufferedReader.readLine()) != null) {
            resp.append(msg);
        }
        return resp.toString();
    }
}

3.2、服务端代码

package com.study.sxf.common.web.socket.io.step1;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * @Date 2022/3/12 1:58 PM
 **/
public class EchoServer {
    private static Integer serverPort = 8080;


    public static void main(String[] args) throws IOException {
        EchoServer echoServer = new EchoServer();
        ServerSocket serverSocket = null;
        try {
            serverSocket = echoServer.buildServerSocket();
            while (true) {
                //step1:接收请求
                Socket socket = serverSocket.accept();
                System.out.println("服务器收到1个客户端请求,客户端地址=" + socket.getInetAddress() + "客户端端口号" + socket.getPort());
                BufferedReader bufferedReader = echoServer.getBufferedReader(socket);
                String req = echoServer.readRequest(bufferedReader);
                System.out.println("客户端发送的请求为=" + req);

                //step2:业务处理
                String resp = req + "服务端已处理成功";

                //step3:进行业务响应
                PrintWriter printWriter = echoServer.getPrintWriter(socket);
                echoServer.ackResponse(printWriter,resp);

                //step4:关闭客户端连接
                System.out.println("服务端关闭连接");
                socket.close();

            }
        } catch (Exception e) {
            System.out.println("服务器异常退出e=" + e.getMessage());
        } finally {
            if (serverSocket != null) {
                serverSocket.close();
            }
        }
    }


    /**
     * 构建1个服务器
     *
     * @return
     * @throws IOException
     */
    private ServerSocket buildServerSocket() throws IOException {
        System.out.println("=======服务器准备启动=====");
        ServerSocket serverSocket = new ServerSocket(serverPort);
        System.out.println("=======服务器启动成功");
        return serverSocket;
    }


    /**
     * 获取输入流，读取客户端请求
     *
     * @param socket
     * @return
     * @throws IOException
     */
    private BufferedReader getBufferedReader(Socket socket) throws IOException {
        InputStream inputStream = socket.getInputStream();
        InputStreamReader reader = new InputStreamReader(inputStream);
        return new BufferedReader(reader);
    }

    /**
     * 读取请求
     *
     * @param bufferedReader
     * @return
     */
    private String readRequest(BufferedReader bufferedReader) throws IOException {
        StringBuffer stringBuffer = new StringBuffer();
        String msg=null;
//        String msg =bufferedReader.readLine();
//        return msg;
        while ((msg = bufferedReader.readLine()) != null) {
            //读取一行后，再读第二行会被阻塞住
            stringBuffer.append(msg);
        }
        return stringBuffer.toString();
    }

    /**
     * 获取输出流管道，进行响应
     *
     * @param socket
     * @return
     * @throws IOException
     */
    private PrintWriter getPrintWriter(Socket socket) throws IOException {
        OutputStream outputStream = socket.getOutputStream();
        return new PrintWriter(outputStream,true);
    }

    private void ackResponse(PrintWriter printWriter, String resp) {
        System.out.println("服务端响应="+resp);
        printWriter.println(resp);
    }
}