PrintWriter调用write方法之后使用flush方法获取不到内容

public void createClientSocket(){
 try {
 BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 Socket s = new Socket("127.0.0.1", 9009);
 PrintWriter pw = new PrintWriter(s.getOutputStream());
 String str = br.readLine();
 while(!"quit".equals(str)){
 //这两行server端可以获取str
 // pw.println(str);
 // pw.flush();
 //这两行server端获取不到str
 pw.write(str);
 pw.flush();
 str = br.readLine();
 }
 } catch (UnknownHostException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
 } catch (IOException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
 }
 }
public void createServerSocket(){
    try {
        ServerSocket ss = new ServerSocket(9009);
        Socket s = ss.accept();
        BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
        String str;
        while((str = br.readLine())!=null){
            System.out.println(str);
        }
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}