服务端与客户端怎么利用socket传文件

package com.ysk;import java.io.BufferedReader;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStreamReader;import java.io.OutputStream;import java.io.OutputStreamWriter;import java.io.PrintWriter;import java.net.ServerSocket;import java.net.Socket;import java.net.UnknownHostException;public class Client {  public static void main(String[] args) {    try {      Socket socket = new Socket("127.0.0.1", 5555);      OutputStream os = socket.getOutputStream();// 字节输出流      PrintWriter pw = new PrintWriter(os);      pw.write("aa.txt");//输入需要搜索的文件名      pw.flush();      socket.shutdownOutput();      BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));      String a = "";      String temp = "";      while ((temp = in.readLine()) != null) {        a += temp;      }      PrintWriter out = new PrintWriter(new OutputStreamWriter(new FileOutputStream("src\\asb.txt")));      out.write(a);      out.flush();      out.close();    } catch (UnknownHostException e) {      e.printStackTrace();    } catch (IOException e) {      e.printStackTrace();    } finally {    }  }}