怎么实现客户端与服务器端 不停的相互发消息

//服务器端

package 通讯;

import java.io.BufferedOutputStream;

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.OutputStream;

import java.io.PrintStream;

import java.io.PrintWriter;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.Scanner;

public class server {

public static void main(String[] args) {

try {

ServerSocket serversocket = new ServerSocket(8888);

System.out.println("正在等待连接。。。。。。。");

Socket socket = serversocket.accept();

while(true){//死循环重复

InputStream is = socket.getInputStream();

InputStreamReader isr = new InputStreamReader(is);

BufferedReader br = new BufferedReader(isr);

String s;

while ((s = br.readLine()) != null) {

System.out.println("客户端说" + s);

}

socket.shutdownInput();

OutputStream os = socket.getOutputStream();

PrintStream bw = new PrintStream(os);

Scanner input = new Scanner(System.in);

System.out.println("你想对对面的客户机说些什么");

bw.print(input.next());//从键盘输入读取一行打印到输出流

bw.flush();

socket.shutdownOutput();

bw.close();

os.close();

br.close();

isr.close();

is.close();

}

} catch (IOException e) {

e.printStackTrace();

}

}

}

//客户端

package 通讯;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.OutputStream;

import java.io.OutputStreamWriter;

import java.io.PrintStream;

import java.net.Socket;

import java.util.Scanner;

public class client {

public static void main(String[] args) {

try {

Socket socket = new Socket("127.0.0.1", 8888);

while (true) {//死循环重复步骤

OutputStream os = socket.getOutputStream();

PrintStream bw = new PrintStream(os);

Scanner input = new Scanner(System.in);

System.out.println("你想对对面的服务器说些什么");

bw.print(input.next());//从键盘输入读取一行 打印到输出流

bw.flush();

socket.shutdownOutput();

InputStream is = socket.getInputStream();

InputStreamReader isr = new InputStreamReader(is);

BufferedReader br = new BufferedReader(isr);

String s;

while ((s = br.readLine()) != null) {

System.out.println("服务器端说：" + s);

}

socket.shutdownInput();

br.close();

isr.close();

is.close();

bw.close();

os.close();

}

} catch (IOException e) {

e.printStackTrace();

}

}

}

为什么这样写死循环 在客户机发给服务器消息 服务器回复后就出现这样的异常？

怎么修改才正确呢？