socket连接的小疑点

package SocketDemo;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.io.PrintWriter;import java.net.Socket;import java.net.UnknownHostException;public class loginClient {    public static void main(String[] args){    try {//建立客户端socket连接 ，指定服务器位置，急端口        Socket socket=new Socket("localhost",8888);        //得到socket的读写流        OutputStream os=socket.getOutputStream();        PrintWriter pw=new PrintWriter(os);        //输入流        InputStream is=socket.getInputStream();        BufferedReader br=new BufferedReader(new InputStreamReader(is));        String info="用户名：tom;用户密码:123456";        pw.write(info);        pw.flush();        socket.shutdownOutput();//关闭输出流                //接受服务器响应        String reply=null;        while(!((reply=br.readLine())==null)){                System.out.println("我是客户端！！服务器端的响应是"+reply);        }        br.close();        is.close();        pw.close();        os.close();        socket.close();    } catch (UnknownHostException e) {        // TODO Auto-generated catch block        e.printStackTrace();    } catch (IOException e) {        // TODO Auto-generated catch block        e.printStackTrace();    }    }}

package SocketDemo;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.io.PrintWriter;import java.net.ServerSocket;import java.net.Socket;public class LoginServer {  public static void main(String [] args){      try {          //建立服务器Socket对象，绑定端口开始监听,建议使用大于1024端口        ServerSocket ss=new ServerSocket(8888);        //使用accpet方法阻塞等待监听，获得连接                Socket socket=ss.accept();        //获得输入流        InputStream is=socket.getInputStream();        BufferedReader br=new BufferedReader(new InputStreamReader(is));        //获得输出流        OutputStream os=socket.getOutputStream();        PrintWriter pw=new PrintWriter(os);                        // 读取输入信息        String info=null;        while(!((info=br.readLine())==null)){                System.out.println("我是服务器！！用户信息为"+info);        }        String reply="welcome";        pw.write(reply);        pw.flush();        pw.close();        os.close();    br.close();    is.close();    socket.close();    ss.close();    } catch (IOException e) {        // TODO Auto-generated catch block        e.printStackTrace();    }  }}