create or replace and compile java source named UDPTry as

import java.io.*;
import java.net.*;

public class UDPTry {
	public static void send(String s,int p) throws SocketException,IOException {
		DatagramSocket ds = new DatagramSocket();
		byte[] buf = s.getBytes();
		InetAddress address = InetAddress.getByName("127.0.0.1");
		DatagramPacket packet = new DatagramPacket(buf, buf.length,address, p);
		ds.send(packet);
	}
	public static String receive(int p) throws SocketException,IOException {
		DatagramSocket ds = new DatagramSocket(p);
		byte[] buf = new byte[256];
		DatagramPacket packet = new DatagramPacket(buf, buf.length);
		ds.receive(packet);
		return new String(packet.getData(), 0, packet.getLength());
	}
}

create or replace package UDP_TRY is
	procedure send(
			string in varchar2,
			port in pls_integer
		) AS LANGUAGE JAVA NAME 'UDPTry.send(java.lang.String,int)';
	function receive(
			port in pls_integer
		) return varchar2 AS LANGUAGE JAVA NAME 'UDPTry.receive(int) return java.lang.String';
end UDP_TRY;

SQL> begin
  2     dbms_output.put_line(udp_try.receive(22));
  3  end;
  4  /

begin
   udp_try.send('HELLO',22);
end;
/

SQL> begin
  2     dbms_output.put_line(udp_try.receive(22));
  3  end;
  4  /
begin
*
ERROR at line 1:
ORA-29532: Java call terminated by uncaught Java exception:
java.net.BindException: bind() failed, errno = 13
Permission denied
ORA-06512: at "ALESSANDRO.UDP_TRY", line 6
ORA-06512: at line 2