Exception in thread "main" java.net.BindException: Address already in use: JVM_Bind

import java.io.PrintStream;
import java.net.Socket;
import java.net.ServerSocket;
import java.util.Scanner;

public class Server
{
    public static void main(String[] args)
        throws Exception
    {
        ServerSocket ss = new ServerSocket(30000);
        Socket socket = ss.accept();
        PrintStream ps = new PrintStream(socket.getOutputStream());
        ps.println("服务器的第一行数据");
        ps.println("服务器的第二行数据");
        // 关闭socket的输出流，表明输出数据已经结束
        socket.shutdownOutput();
        // 下面语句将输出false，表明socket还未关闭。
        System.out.println(socket.isClosed());
        Scanner scan = new Scanner(socket.getInputStream());
        while (scan.hasNextLine())
        {
            System.out.println(scan.nextLine());
        }
        scan.close();
        socket.close();
        ss.close();
    }
}

运行上面代码，出现下面错误：

ServerSocket ss = new ServerSocket(30000);//错误在这一行，表明30000端口被占用，原因是可能有程序在占用30000端口，你可以换个端口试一试！