关于java socket的问题

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？？