Trying to send UDP discovery packet

[JohnST]

I've looked everywhere online and have gone through tutorials still with no luck. I realize there is something wrong with IPAddress in the datagram packet. What I can't figure out either is how I can change the socketserver to listen on local port 31337. I'm trying to do the Java equivalent of this I REMOVED THE LINK display the ipaddress of the controller. I realize I still have a lot to learn. I just want to work on something more appealing at the moment.

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

class UDPc4 {
public static void main(String args[]) throws Exception{

DatagramSocket clientSocket = new DatagramSocket();

InetAddress IPAddress = InetAddress.getByName("host");
byte[] sendData = new byte[512];
byte[] receiveData = new byte[512];

String message = "M-SEARCH * HTTP/1.1\r\n"
+ "HOST: 239.255.255.250:1900\r\n"
+ "MAN: \"ssdp:discover\"\r\n"
+ "MX: 5\r\n"
+ "ST: c4:director\r\n"
+ "\r\n";

sendData = message.getBytes();

DatagramPacket packet =
new DatagramPacket(sendData, sendData.length, IPAddress, 1900);


clientSocket.send(packet);


packet = new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(packet);
String received = new String(packet.getData(), 0,packet.getLength());
System.out.println("Controller found " + received);
}
}

[JohnST]

Ok I am getting a response. How do I get the IP address?

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

class UDPc4 {
 public static void main(String args[]) throws Exception
 
 {
 DatagramSocket clientSocket = new DatagramSocket(21557);
 InetAddress group = InetAddress.getByName("239.255.255.250");


 byte[] sendData = new byte[0];
 byte[] receiveData = new byte[128];
 String sentance = "M-SEARCH * HTTP/1.1\r\n"
 + "HOST: 239.255.255.250:1900\r\n"
 + "MAN: \"ssdp:discover\"\r\n"
 + "MX: 5\r\n"
 + "ST: c4:director\r\n"
 + "\r\n";
     
 sendData = sentance.getBytes();

 DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, group, 1900);

 clientSocket.send(sendPacket);
 System.out.println("sent packet...");
 DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);

 clientSocket.receive(receivePacket);

 String controllerResponse = new String(receivePacket.getData());
 
 System.out.println("response:\n" +controllerResponse);
 clientSocket.close();
 }

}