// This example is from _Java Examples in a Nutshell_. (http://www.oreilly.com)
// Copyright (c) 1997 by David Flanagan
// This example is provided WITHOUT ANY WARRANTY either expressed or implied.
// You may study, use, modify, and distribute it for non-commercial purposes.
// For any commercial use, see http://www.davidflanagan.com/javaexamples

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

/**
 * This class sends the specified text or file as a datagram to the 
 * specified port of the specified host.
 **/
public class UDPSend {
  public static void main(String args[]) {
    try { 
      // Check the number of arguments
      if (args.length < 3) 
        throw new IllegalArgumentException("Wrong number of arguments");
      
      // Parse the arguments
      String host = args[0];
      int port = Integer.parseInt(args[1]);

      // Figure out the message to send.  
      // If the third argument is -f, then send the contents of the file
      // specified as the fourth argument.  Otherwise, concatenate the 
      // third and all remaining arguments and send that.
      byte[] message;
      if (args[2].equals("-f")) {
        File f = new File(args[3]);
        int len = (int)f.length();    // figure out how big the file is
        message = new byte[len];      // create a buffer big enough
        FileInputStream in = new FileInputStream(f);
        int bytes_read = 0, n;
        do {                          // loop until we've read it all
          n = in.read(message, bytes_read, len-bytes_read);
          bytes_read += n;
        } while((bytes_read < len) && (n != -1));
      }
      else { // Otherwise, just combine all the remaining arguments.
        String msg = args[2];  
        for (int i = 3; i < args.length; i++) msg += " " + args[i];
        message = msg.getBytes();
      }
      
      // Get the internet address of the specified host
      InetAddress address = InetAddress.getByName(host);

      // 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);
      System.err.println("Usage: java UDPSend <hostname> <port> <msg>...\n" +
                         "   or: java UDPSend <hostname> <port> -f <file>");
    }
  }
}