JAVA - Can't make a UDP packets reach it destination with the code, but it works in "Packet Sender", Wireshark shows the same status - sockets

Question

I'm trying to send a UDP packet over a local network in my workplace.
until now I used a program called "Packet Sender", and it worked fine, but my boss asked me to write a code in Java that does the same.
When the packet arrives to its destination it turns off one of the lights in the office (like in Home automation).
Since the light isn't turned off with my code and only with packet sender I understand that something is wrong, but I don't know what.
I wrote this code:
import java.io.*;
import java.net.*;
import javax.xml.bind.annotation.adapters.HexBinaryAdapter;
public class UDPSend
{
public static void main(String args[])
{
try {
int port = 6670;
//Send Hex As Bytes
HexBinaryAdapter adapter = new HexBinaryAdapter();
byte[] message = adapter.unmarshal("020000c818010000020300");
// Get the internet address of the specified host
InetAddress address = InetAddress.getByName("172.16.254.254");
// Initialize a datagram packet with data and address
DatagramPacket packet = new DatagramPacket(message, message.length,
address, port);
// Create a datagram socket, send the packet through it, close it.
DatagramSocket dsocket = new DatagramSocket();
dsocket.send(packet);
dsocket.close();
} catch (Exception e) {
System.err.println(e);
}
}
}
now just so you'll can understand my problem better, here are some printscreens:
www32.speedyshare.com/PrUcv/download/stack-over-flow.png
1] - The wireshark printscreen when I run my code.
2] - The Packet Sender with all the data to send.
3] - the Packet Sender log in which you can see it sent the packet and it did what it
supposed to do.
4] - the Wireshark monitor when I run the packet sender application.
IMPORTANT!!
1. I'm trying to run the code in the office network.
2. I KNOW the 2 last chars in the packet sender is 01 and in the JAVA code is
00, it's OK! one turn the light on and the other one off, either
way it works with packet sender but not with my code.
3. Wireshark shows a bad checksum to my code as well to the packet sender app, the difference is that when I use the packet sender it works despite the bad checksum.