在Java Socket上设置源端口？

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;

public class DatagramSocketExample {
    public static void main(String[] args) {
        try {
            // 创建DatagramSocket实例，并指定端口号和网络地址
            DatagramSocket socket = new DatagramSocket(12345, InetAddress.getByName("127.0.0.1"));

            // 创建数据包
            byte[] data = "Hello, world!".getBytes();
            DatagramPacket packet = new DatagramPacket(data, data.length, InetAddress.getByName("127.0.0.1"), 54321);

            // 发送数据包
            socket.send(packet);

            // 接收数据包
            byte[] buffer = new byte[1024];
            DatagramPacket receivedPacket = new DatagramPacket(buffer, buffer.length);
            socket.receive(receivedPacket);

            // 输出接收到的数据
            String receivedData = new String(receivedPacket.getData(), 0, receivedPacket.getLength());
            System.out.println("Received data: " + receivedData);

            // 关闭DatagramSocket
            socket.close();
        } catch (SocketException e) {
            e.printStackTrace();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}