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/*******************************************************************************
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 * File: P2_Server.java
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 * Author: Ira W. Snyder (devel@irasnyder.com)
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 * License: GNU General Public License v2
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 * Class: CS380 - Computer Networking
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 *
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 * Assignment: Project #2
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 * Date Last Modified: 2006-02-05
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 *
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 * Purpose: Implement a simple server which will listen on UDP port 1337 for
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 * incoming datagrams. It will first recieve a message telling it to drop
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 * every n-th message. After that it will convert every message it recieves
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 * from 4B to 5B encoding, and reply back to the client. It will only exit on
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 * receiving the message "QUIT".
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 ******************************************************************************/
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import java.io.*;
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import java.io.*;
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import java.util.*;
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import java.util.*;
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import java.net.*;
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import java.net.*;
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import java.util.regex.*;
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import java.util.regex.*;
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public class P2_Server
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public class P2_Server
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{
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{
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    private static int portNumber = 1337;
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    private static int portNumber = 1337;
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    private static int dropEvery = -1;
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    private static int dropEvery = -1;
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    private static int sendCount = 1;
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    private static int sendCount = 0;
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    private static DatagramPacket packet;
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    private static DatagramPacket packet;
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    private static DatagramSocket socket;
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    private static DatagramSocket socket;
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    /**
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     * Method: readPacket()
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     * Purpose: Read a packet from the currently opened socket.
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     * Note: Blocks until it recieves data.
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     */
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    public static String readPacket (int maxlen)
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    public static String readPacket (int maxlen)
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    {
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    {
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        byte[] buf = new byte[maxlen];
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        byte[] buf = new byte[maxlen];
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        packet = new DatagramPacket (buf, buf.length);
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        packet = new DatagramPacket (buf, buf.length);
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        }
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        }
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        System.out.println ("Recieved Packet. Len: " + packet.getLength());
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        System.out.println ("Recieved Packet. Len: " + packet.getLength());
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        String s = new String (buf, 0, packet.getLength() /*- 1*/);
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        String s = new String (buf, 0, packet.getLength() /*- 1*/);
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        System.out.println ("RcvdPacket: |" + s + "|");
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        return s;
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        return s;
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    }
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    }
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    /**
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     * Method: writePacket()
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     * Purpose: write a message to the last client that sent us a message,
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     * while dropping every n-th message, as specified by the client.
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     */
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    public static boolean writePacket (String msg)
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    public static boolean writePacket (String msg)
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    {
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    {
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        if (sendCount == dropEvery && !msg.equals("QUIT"))
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        if (sendCount == dropEvery && !msg.equals("QUIT"))
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        {
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        {
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            System.out.println ("Dropped a packet");
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            System.out.println ("Dropped a packet");
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            sendCount = 0; // reset the sendCount
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            sendCount = 0; // reset the sendCount
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            return true;   // "Fake" send
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            return true;   // "Fake" send
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        }
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        }
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        else { sendCount++; }
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        else { sendCount++; }
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        System.out.println ("Num sent: " + sendCount);
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        InetAddress address = packet.getAddress();
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        InetAddress address = packet.getAddress();
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        int port = packet.getPort();
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        int port = packet.getPort();
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        byte[] buf = msg.getBytes();
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        byte[] buf = msg.getBytes();
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        packet = new DatagramPacket (buf, buf.length, address, port);
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        packet = new DatagramPacket (buf, buf.length, address, port);
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        }
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        }
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        return true;
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        return true;
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    }
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    }
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    /**
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     * Method: calcDrops()
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     * Purpose: Parse a message sent by the client telling us to drop
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     * every n-th message.
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     */
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    public static int calcDrops (String s)
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    public static int calcDrops (String s)
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    {
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    {
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        String dropRegex = "^DROP(\\d*)(.*)$";
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        String dropRegex = "^DROP(\\d*)(.*)$";
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        Pattern p = Pattern.compile(dropRegex);
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        Pattern p = Pattern.compile(dropRegex);
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        Matcher m = p.matcher(s);
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        Matcher m = p.matcher(s);
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            return Integer.parseInt(m.group(1));
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            return Integer.parseInt(m.group(1));
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        return -1;
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        return -1;
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    }
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    }
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    /**
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     * Method: main()
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     * Purpose: Open a listening UDP socket, and convert a client's
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     * requests from 4B encoding to 5B encoding.
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     */
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    public static void main (String[] args) throws Exception
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    public static void main (String[] args) throws Exception
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    {
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    {
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        boolean done = false;
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        boolean done = false;
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        socket = new DatagramSocket(portNumber);
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        socket = new DatagramSocket(portNumber);
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        packet = null;
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        packet = null;
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            if (dropEvery != -1)
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            if (dropEvery != -1)
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            {
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            {
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                done = true;
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                done = true;
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                System.out.println ("dropEvery: " + dropEvery);
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                System.out.println ("dropEvery: " + dropEvery);
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            }
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            }
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            writePacket (s);
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        }
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        }
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        done = false;
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        done = false;
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        // Keep reading until we get a quit packet
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        // Keep reading until we get a quit packet
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                s = "BADVAL";
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                s = "BADVAL";
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            }
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            }
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            writePacket (s);
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            writePacket (s);
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        }
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        }
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        // Close the socket
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        socket.close();
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    }
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    }
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}
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}
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