TCP程序(Java)中的问题

有人能帮我调试这个程序吗?

以下是服务器代码:

package networking;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;

class TcpServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(5555);
        while (true) {
            Socket client = serverSocket.accept();
            Scanner reader = new Scanner(client.getInputStream());
            PrintWriter writer = new PrintWriter(client.getOutputStream());
            String inputString = reader.nextLine();
            System.out.println("Received from client : " + inputString);
            writer.write(inputString.toUpperCase());
            client.close();
        }
    }
}

这是客户代码:

package networking;

import java.io.PrintWriter;
import java.io.IOException;
import java.net.Socket;
import java.util.Scanner;

class TcpClient {
    public static void main(String[] args) throws IOException {
        Socket client = new Socket("localhost", 5555);
        PrintWriter writer = new PrintWriter(client.getOutputStream());
        Scanner reader=new Scanner(client.getInputStream());
        writer.println("oPen SOurCe RUleS !");
        System.out.println("Received from server : "+reader.nextLine());
        client.close();
    }
}

问题是,当我运行这个程序时,客户机和服务器都进入不确定的等待状态。有人能告诉我这个代码有什么问题吗?

事先谢谢!