socket监听输入流怎么关闭

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

public class Server{
public static void main(String[] args){

    InputStream in=null;
    OutputStream out=null;
    try{
        ServerSocket ss=new ServerSocket(8888);
        Socket socket=ss.accept();
        in=socket.getInputStream();
        out=socket.getOutputStream();
        DataOutputStream dos=new DataOutputStream(out);
        DataInputStream dis=new DataInputStream(in);
        String s=null;
        if((s=dis.readUTF())!=null){
            System.out.println(s);
        }
        /*
        System.out.println(dis.readUTF())
        */

        String fileContent = readFileContent("E:\\LQ.txt");;
        dos.writeUTF(fileContent);
        dis.close();
        dos.close();
        socket.close();
    }catch(IOException e) {
        e.printStackTrace();
    }

 }

private static String readFileContent(String fileName) throws IOException {
    File file = new File(fileName);
    BufferedReader bf = new BufferedReader(new FileReader(file));
    String content = "";
    StringBuilder sb = new StringBuilder();
    while(content != null){
        content = bf.readLine();
        if(content == null){
            break;
        }
        sb.append(content.trim());
    }
    bf.close();
    return sb.toString();
}
}

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

public class Client{
public static void main(String[] args){

    InputStream is=null;
    OutputStream os=null;
    try{
        Socket socket=new Socket("localhost",8888);
        is=socket.getInputStream();
        os=socket.getOutputStream();
        DataInputStream dis=new DataInputStream(is);
        DataOutputStream dos=new DataOutputStream(os);
        dos.writeUTF("hello");
        String s=null;
        if((s=dis.readUTF())!=null);
        System.out.println(s);
        dis.close();
        dos.close();
        socket.close();
    }catch(IOException e) {e.printStackTrace();}
}
}