UDP 地址已在使用中?

I am following the UDP tutorials at http://docs.oracle.com/javase/tutorial/networking/datagrams/broadcasting.html ,I have copied all the code and compiled it, now If I compile the client first and then the server, the server prints this out in console

Exception in thread "main" java.net.BindException: Address already in use: Cannot bind
at java.net.PlainDatagramSocketImpl.bind0(Native Method)
at java.net.PlainDatagramSocketImpl.bind(Unknown Source)
at java.net.DatagramSocket.bind(Unknown Source)
at java.net.DatagramSocket.<init>(Unknown Source)
at java.net.DatagramSocket.<init>(Unknown Source)
at java.net.DatagramSocket.<init>(Unknown Source)
at QuoteServerThread.<init>(QuoteServerThread.java:19)
at MulticastServerThread.<init>(MulticastServerThread.java:10)
at MulticastServer.main(MulticastServer.java:3)

QuoteServerThread 第 19 行是

socket = new DatagramSocket(12345);

public MulticastServerThread() throws IOException {
    super("MulticastServerThread"); // line 10
}

public class MulticastServer {
    public static void main(String[] args) throws java.io.IOException {
        new MulticastServerThread().start(); // line 3
    }
}

Exception in thread "main" java.net.BindException: Address already in use: Cannot bind
at java.net.PlainDatagramSocketImpl.bind0(Native Method)
at java.net.PlainDatagramSocketImpl.bind(Unknown Source)
at java.net.DatagramSocket.bind(Unknown Source)
at java.net.MulticastSocket.<init>(Unknown Source)
at java.net.MulticastSocket.<init>(Unknown Source)
at MulticastClient.main(MulticastClient.java:9)

MulticastSocket socket = new MulticastSocket(12345);