UDPSend.java Source code

Introduction

Here is the source code for UDPSend.java

Source

/*
 * Copyright (c) 2004 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 3nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose,
 * including teaching and use in open-source projects.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book, 
 * please visit http://www.davidflanagan.com/javaexamples3.
 */
//package je3.net;
import java.io.File;
import java.io.FileInputStream;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

/**
 * This class sends the specified text or file as a datagram to the specified
 * port of the specified host.
 */
public class UDPSend {
    public static final String usage = "Usage: java UDPSend <hostname> <port> <msg>...\n"
            + "   or: java UDPSend <hostname> <port> -f <file>";

    public static void main(String args[]) {
        try {
            // Check the number of arguments
            if (args.length < 3)
                throw new IllegalArgumentException("Wrong number of args");

            // 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];
                // Convert the message to bytes using UTF-8 encoding
                message = msg.getBytes("UTF-8");
            }

            // 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);
        }
    }
}