Sends the specified text or file as a datagram to the specified port of the specified host : DatagramPacket « Network Protocol « Java

Sends the specified text or file as a datagram to the specified port of the specified host

 * 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

 * 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 =, 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();
    } catch (Exception e) {


Related examples in the same category

1.Get data from DatagramPacket
2.Get address and port from DatagramPacket
3.Create DatagramPacket from byte array
4.Waits to receive datagrams sent the specified portWaits to receive datagrams sent the specified port