关于java socket的问题

要做成这样的：

客户端访问服务器ip和port，服务器马上发送welcome消息，然后客户端根据welcome消息判断是否是想要连接的服务器和端口，

如果是则开始发送数据，数据包括开始和结束的校验。服务器端发送welcome消息后开始接收数据，直到结束。蛮简单的事TMD我怎么就搞不定。

CLIENT：

package com.ces.mytest.socket;

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

public class ClientThread extends Thread {
    private String ipStr = "";
    private int port;
    public ClientThread(String ipStr, int port) {
        this.ipStr = ipStr;
        this.port = port;
    }

    public void run() {
        try {
            Socket client = new Socket(ipStr, port);
            BufferedReader read = new BufferedReader(new InputStreamReader(client.getInputStream()));
            BufferedWriter write = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));

            if ("欢迎".equals(read.readLine())) {
                System.out.println("校验正确");

                write.write("开始");
                write.newLine();
                write.write("数据");
                write.newLine();
                write.write("结束");
                write.newLine();
                write.flush();

                System.out.println("发送完毕");
            }

            write.close();
            read.close();
            client.close();
        } catch (UnknownHostException ex) {
            ex.printStackTrace();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public static void main(String[] args) {
        Thread client = new ClientThread("127.0.0.1",10020);
        client.start();
    }

}

SERVER：

package com.ces.mytest.socket;

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

public class ServerThread extends Thread {
    private int port;
    public ServerThread(int port) {
        this.port = port;
    }

    private boolean stop = false;

    public void run() {
        try {
            ServerSocket server = new ServerSocket(port);
            while (!stop) {
                Socket client = server.accept();
                BufferedReader read = new BufferedReader(new InputStreamReader(client.getInputStream()));
                BufferedWriter write = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
               
                System.out.println("发送欢迎信息");
               
                write.write("欢迎");
                write.flush();

//                String lineStr = read.readLine();
//                if ("开始".equals(lineStr)) {
//                    System.out.println("开始接受数据！");
//
//                    while (true) {
//                        lineStr = read.readLine();
//                        if ("结束".equals(lineStr)) {
//                            break;
//                        } else {
//                            System.out.println("数据是" + lineStr);
//                        }
//                    }
//                }

                write.close();
                read.close();
                client.close();
            }

        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public static void main(String[] args) {
        Thread server = new ServerThread(10020);
        server.start();
    }

    public boolean isStop() {
        return stop;
    }

    public void setStop(boolean stop) {
        this.stop = stop;
    }
}

只要我将ServerThread类的String lineStr = read.readLine();的注释去掉，程序肯定出问题，什么问题呢？分析发现ServerThread的Output流必须等write.close()执行完才发送，而read.readLine()程序就会停在那里，所谓的block程序，可参考上明明说write.flush()即可发送啊，搞不懂搞不懂，这样我的握手协议怎么做啊？？

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