rreq.java

DSr project for the java applications

package dsr;


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

//this implements the code for the generation and the reception of the RREQ packets.
public class RREQ {
  //this function handles the reception of the RREQ packets. It first decodes the datagrampacket
  //to get the RREQ packet. increases the hop count by 1. It first checks if this request
  //has been received before as well. if not then this packet has to be handled. so if i am the
  //destination for this RREQ packet then i generate a RREP packet and send it to the source
  //otherwise the RREQ packet is updated and locally broadcasted.
  public static void recvRREQ(EventQueueEntry workingEvent) throws UnknownHostException {
    //get the packet first
    System.out.println("inside the recvRREQ ::::::::::::::::::::::::::::::");
    System.out.println("the packet was revceived from: " + workingEvent.packet.getAddress());

    RREQPacket rreq = new RREQPacket();
    rreq = rreq.decode(workingEvent.packet);

    //update the hopCount by 1
    rreq.hopCount++;

    System.out.println("the packet in RREQ is " + rreq.toString());
    System.out.println("the packet in RREQ is " + rreq.floodID);
   //find what interface the packet was received on
    InetAddress localAddress = workingEvent.dstIP;

    //look in the flood ID Queue to find out if the request was already received.
    FloodIDQueueEntry tmpFloodEntry =
        FloodIDQueue.findFloodIDQueueEntry(rreq.dstIPAddr, rreq.floodID);

    FloodIDQueue.PrintFloodIDQueue();

    //Insert this packet to the floodIDQueue if it has to be dealt with
    if (tmpFloodEntry != null)  {
      System.out.println("i am also looking for that address");
      return;
    }

    long currTime = System.currentTimeMillis();
    FloodIDQueue.insertFloodIDQueueEntry(rreq.srcIPAddr, rreq.dstIPAddr, rreq.floodID,
        currTime + Const.PATH_TRAVERSAL_TIME);

    //update reverse route entry
    RouteTable.updateReverseRouteTableEntry(workingEvent);

    //if route table has an valid entry to the destination
    int pos = RouteTable.FindRouteTableEntry(rreq.dstIPAddr);
    if (pos != -1) { //there is a valid entry or i, myself am the destination
      //generate a RREP and send it back
      RREP.genRREP(rreq, workingEvent.srcIP);
      System.out.println("generated an RREP message and is send back to the client");
      //add code to send back the RREP to the node from where it was received.
      //the address can be obtained from the route table.
    }
    else {
      //else update the RREQ and do a local broadcast
      System.out.println("updated RREQ and done a locabroadcast");
      RREQPacket outRREQ = new RREQPacket((byte)1, rreq.flags, rreq.hopCount,
          rreq.dstIPAddr, rreq.dstSeqNum, rreq.srcIPAddr, rreq.srcSeqNum);
      outRREQ.floodID = rreq.floodID;
      try {
        localBroadcast(outRREQ);
      } catch (UnknownHostException e) {}
    }
  }

  //this function takes care of the generation of the RREQ packets. It first checks in this
  //RREQ has already been generated. So if not, then create a new RREQ packet, insert that in
  //the floodID queue so that one can take care of duplicate RREQ packets. So enter that in the
  //timer queue so that retries can be made.. and then broad cast locally
  public static void genRREQ(InetAddress src, InetAddress dest) {
    //need to check if this RREQ has already been generated
    if (TimerQueue.checkForThisRREQInTimerQueue(src, dest, Const.EVENT_RREQ)) {
      return;
    }

    //create the RREQ packet
    RREQPacket outRREQ = new RREQPacket((byte)1, Const.EVENT_RREQ, (byte)0, dest, 0, src, 0);

    //insert it in the floodID queue so as to prevent duplicate packets
    FloodIDQueue.insertFloodIDQueueEntry(src, dest, outRREQ.floodID,
        Const.PATH_TRAVERSAL_TIME + System.currentTimeMillis());

    FloodIDQueue.PrintFloodIDQueue();
    //inseert it in the timer queue so that we can take care of the time till which time the
    //previously generated RREQ is valid
    TimerQueue.insertInTimerQueue(System.currentTimeMillis() + Const.PATH_TRAVERSAL_TIME,
                                  src, dest, (byte)2, Const.RREQ_TYPE);
    TimerQueue.PrintTimerQueue();

    try {
      localBroadcast(outRREQ);
    } catch (UnknownHostException e) {}
  }

  //code for the local broad cast of the RREQ packet
  public static void localBroadcast(RREQPacket rreq) throws UnknownHostException {
    System.out.println("inside localbraodcast");
    InetAddress broadcastAddress = InetAddress.getByName("255.255.255.255");
    byte[] bytesToSend = rreq.encode(rreq);
    DatagramPacket sendPacket = new DatagramPacket(bytesToSend, bytesToSend.length,
          broadcastAddress, Const.DSRPORT);

    InetAddress localAddress =
        ((InterfaceListEntry)InterfaceList.interfaceList.lastElement()).ipAddress;
    try{
      DatagramSocket sock = new DatagramSocket(0, localAddress);
      try {
        sock.send(sendPacket);
      }catch (IOException e) {}
    } catch (SocketException e) {}
  }
}