服务器不从客户端套接字接收输出

Question

我正在尝试测试我的服务器以接收来自客户端的输出，适用于Linux终端，但是当我尝试传递另一个代码时，我总是收到空值。

这是我用来接收输入的方法：

public String receiveString() throws IOException{
    BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
    PrintWriter out = new PrintWriter (new OutputStreamWriter(client.getOutputStream()));
    String input = null;
    try{
        input = in.readLine();
        System.out.println("Inside:"+input);
        return input;
    }catch(NullPointerException e) {
        out.println("4");
        out.flush(); 
        client.close();
    } finally {

    }
    return input;
}

当我通过终端传递输出时，工作正常，但是当我通过上面的代码传递时，不工作，receiveString总是显示Null。

public static void main(String[] args ) throws IOException {
    Socket client = null;
    try {
        client = new Socket("localhost", 12009);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    BufferedReader in = new BufferedReader (new InputStreamReader(client.getInputStream()));
    PrintWriter out = new PrintWriter (new OutputStreamWriter(client.getOutputStream()));
    out.println("Test");  
    out.flush();
    client.close();
}

所有连接都工作正常，只是这部分代码有问题......