请问一个socket 程序有关问题

请教一个socket 程序问题？
想实现这样的效果，client   不断的向server   发送消息，server   接收到消息之后原路返回般的给client   写些信息。请问该如何实现？

------解决方案--------------------
import java.net.*;
import java.io.*;
import java.lang.*;

public class myserver{
public static void main(String args[]){
ServerSocket server;
Socket socket;
String s;
InputStream Is;
OutputStream Os;
DataInputStream DIS;
PrintStream PS;

try{
//在端口4321注册服务
server=new ServerSocket(4321);
socket=server.accept(); 　　//监听窗口,等待连接

System.out.println( "server ok ");
System.out.println( "************************************************ ");
System.out.println( " ");

//获得对应Socket的输入/输出流
Is=socket.getInputStream();
Os=socket.getOutputStream();
//建立数据流
DIS=new DataInputStream(Is);
PS=new PrintStream(Os);
DataInputStream in=new DataInputStream(System.in);
while(true){
System.out.println( " ");
System.out.println( "please wait client 's message... ");
System.out.println( " ");
s=DIS.readLine(); //读入从client传来的字符串
System.out.println( "client said: "+s); //打印字符串
if(s.trim().equals( "BYE "))break; //如果是 "BYE ",就退出
System.out.print( "you say: ");
s=in.readLine(); //读取用户输入的字符串
PS.println(s); //将读取得字符串传给client
if(s.trim().equals( "BYE "))break; //如果是 "BYE ",就退出

}

//关闭连接
DIS.close(); //关闭数据输入流
PS.close(); //关闭数据输出流
Is.close(); //关闭输入流
Os.close(); //关闭输出流
socket.close(); //关闭sockey
}
catch(Exception e){
System.out.println( "Error: "+e);
}
}
}


通话器客户端
import java.net.*;
import java.io.*;
import java.lang.*;

public class myclient{
public static void main(String args[]){
if (args.length <1){ //判断命令加参数没有
System.out.println( "you forget the name of the server! ");
System.out.println( "see also: myclient yxf ");
System.exit(1); //如果没加参数就退出
}

Socket socket;
String s= "yxfsoft@263.net ";
String len;
InputStream Is;
OutputStream Os;
DataInputStream DIS;
PrintStream PS;
try{
//向主机名为args[0]的服务器申请连接
//注意端口号要与服务器保持一致:4321
socket=new Socket(args[0],4321);

System.out.println( "client ok ");
System.out.println( "************************************************ ");
System.out.println( " ");

//获得对应socket的输入/输出流
Is=socket.getInputStream();
Os=socket.getOutputStream();
//建立数据流
DIS=new DataInputStream(Is);
PS=new PrintStream(Os);
DataInputStream in=new DataInputStream(System.in);

while(true){
System.out.print( "you say: ");
s=in.readLine(); //读取用户输入的字符串
PS.println(s); //将读取得字符串传给server
if(s.trim().equals( "BYE "))break; //如果是 "BYE ",就退出
else
{
System.out.println( " ");
System.out.println( "please wait server 's message... ");
System.out.println( " ");
}
s=DIS.readLine(); //从服务器获得字符串
System.out.println( "server said: "+s); //打印字符串
if(s.trim().equals( "BYE "))break; //如果是 "BYE ",就退出

}

//关闭连接
DIS.close(); //关闭数据输入流
PS.close(); //关闭数据输出流
Is.close(); //关闭输入流
Os.close(); //关闭输出流
socket.close(); //关闭socket
}
catch(Exception e){