A simple UDP packet sending command line application.

UDPServer.java

import java.io.*;
import java.net.*;
import java.util.Scanner;

class UDPServer
{
   public static void main(String args[]) throws Exception
   {   
    Scanner in = new Scanner(System.in);
    
    System.out.println("Enter UDP client IP address:");
    String ip = in.nextLine();
    
    InetAddress ipAddress = InetAddress.getByName(ip); // Attempt connection to UDP client
    boolean running = false;
    
    if (ipAddress.isReachable(3000)) {
      System.out.println("Connected: " + ipAddress.toString()); 
      running = true;
    } else {
      System.out.println("Error establishing connection.");
    }   
    
    DatagramSocket clientSocket = new DatagramSocket(); // Socket for sending data
    
    clientSocket.connect(ipAddress, 2390); // IP address and port
    
    while (running) {
      BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
    
      System.out.println("Enter data:");
          
      String data = inFromUser.readLine();
          
      if (data == "exit") {
        System.out.println("Goodbye");
        running = false;
      }   
      else {
        System.out.println("Sending data...");
            
        byte[] sendData = new byte[255];
        sendData = data.getBytes();
            
        DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length);
            
        clientSocket.send(sendPacket);
            
        System.out.println("Data sent.");
      }   
    }   
    
    clientSocket.close();
   }   
}