udpsend.java

java 的164个例子的源代码,包括了 很多方面,供包括了19个方面的 源代码

/*
 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd 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.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book (recommended),
 * visit http://www.davidflanagan.com/javaexamples2.
 */
package com.davidflanagan.examples.net;
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 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];
                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);
        }
    }
}