udpecho.java

J2ME MIDP_Example_Applications

// Copyright 2003 Nokia Corporation. 
// 
// THIS SOURCE CODE IS PROVIDED 'AS IS', WITH NO WARRANTIES WHATSOEVER, 
// EXPRESS OR IMPLIED, INCLUDING ANY WARRANTY OF MERCHANTABILITY, FITNESS 
// FOR ANY PARTICULAR PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE 
// OR TRADE PRACTICE, RELATING TO THE SOURCE CODE OR ANY WARRANTY OTHERWISE 
// ARISING OUT OF ANY PROPOSAL, SPECIFICATION, OR SAMPLE AND WITH NO 
// OBLIGATION OF NOKIA TO PROVIDE THE LICENSEE WITH ANY MAINTENANCE OR 
// SUPPORT. FURTHERMORE, NOKIA MAKES NO WARRANTY THAT EXERCISE OF THE 
// RIGHTS GRANTED HEREUNDER DOES NOT INFRINGE OR MAY NOT CAUSE INFRINGEMENT 
// OF ANY PATENT OR OTHER INTELLECTUAL PROPERTY RIGHTS OWNED OR CONTROLLED 
// BY THIRD PARTIES 
// 
// Furthermore, information provided in this source code is preliminary, 
// and may be changed substantially prior to final release. Nokia Corporation 
// retains the right to make changes to this source code at 
// any time, without notice. This source code is provided for informational 
// purposes only. 
// 
// Nokia and Nokia Connecting People are registered trademarks of Nokia
// Corporation.
// Java and all Java-based marks are trademarks or registered trademarks of
// Sun Microsystems, Inc.
// Other product and company names mentioned herein may be trademarks or
// trade names of their respective owners.
// 
// A non-exclusive, non-transferable, worldwide, limited license is hereby 
// granted to the Licensee to download, print, reproduce and modify the 
// source code. The licensee has the right to market, sell, distribute and 
// make available the source code in original or modified form only when 
// incorporated into the programs developed by the Licensee. No other 
// license, express or implied, by estoppel or otherwise, to any other 
// intellectual property rights is granted herein.


// unnamed package

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


// This is a very simple server intended for simple testing only

public class UDPEcho
{
    private static final int MAX_PACKET_SIZE = 65507;  // max possible for UDP
    private static boolean quietMode = false;


    public static void main(String[] args)
    {
        if ((args.length > 0) && "-q".equals(args[0]))
        {
            quietMode = true;
            args = shift(args);
        }

        if (args.length != 1)
        {
            System.err.println("Usage: java UDPEcho [-q] <local-port>");
            System.err.println(" -q: quiet mode (don't print out packets)");
            System.exit(1);
        }

        int localPort = 0;
        try
        {
            localPort = Integer.parseInt(args[args.length - 1]);
        }
        catch (NumberFormatException ex)
        {
            System.err.println("Invalid number: \"" +
                               args[args.length - 1] + "\"");
            System.exit(1);
        }

        try
        {
            DatagramSocket socket = new DatagramSocket(localPort);
            byte[] receiveBuffer = new byte[MAX_PACKET_SIZE];
            DatagramPacket receivePacket =
                new DatagramPacket(receiveBuffer, receiveBuffer.length);
            while (true)
            {
                log("Entering receive:");
                socket.receive(receivePacket);
                log("Packet received");

                int length = receivePacket.getLength();
                InetAddress remoteAddress = receivePacket.getAddress();
                int remotePort = receivePacket.getPort();

                logPacket(remoteAddress, remotePort, receiveBuffer, length);

                // Echo by sending back exactly the same data
                DatagramPacket sendPacket =
                    new DatagramPacket(receiveBuffer,
                                       length,
                                       remoteAddress,
                                       remotePort);
                log("Entering send");
                socket.send(sendPacket);
                log("Echo packet sent");
                receivePacket.setLength(receiveBuffer.length);
            }
        }
        catch (IOException ex)
        {
            System.err.println("I/O Exception: " + ex.getMessage());
            ex.printStackTrace(System.err);
            System.exit(1);
        }

        System.exit(0);
    }


    private static String[] shift(String[] args)
    {
        String[] newArgs;
        if (args.length == 0)
        {
            newArgs = args;
        }
        else
        {
            newArgs = new String[args.length - 1];
            System.arraycopy(args, 1, newArgs, 0, args.length - 1);
        }
        return newArgs;
    }


    private static void log(String str)
    {
        if (!quietMode)
        {
            System.out.println(str);
        }
    }


    private static void logPacket(InetAddress remoteAddress,
                                  int remotePort,
                                  byte[] data,
                                  int length)
    {
        if (!quietMode)
        {
            System.out.println("  From address: " + remoteAddress);
            System.out.println("  From port: " + remotePort);
            System.out.println("  Data length: " + length);
            System.out.println("  Data: \"" +
                               printable(data, 0, length) + "\"");
        }
    }


    // very conservative method for printing a byte array
    private static String printable(byte[] data, int offset, int length)
    {
        StringBuffer buf = new StringBuffer(length);
        for (int i = offset; i < length; ++i)
        {
            char ch = (char)(data[i] & 0xFF);
            if ((ch >= 0x20) && (ch <= 0x7E))  // Only US-ASCII
            {
                buf.append(ch);
            }
            else
            {
                buf.append('?');
            }
        }
        return buf.toString();
    }
}