rreqpacket.java

DSr project for the java applications

package dsr;


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

//this implements the RREQ packet
class RREQPacket {
  public byte type;              //this is for the type of packet. again not required.
  public short flags;            //implements the various flags..
  public byte hopCount;          //hop count
  public int floodID;            //unique flood ID to identify the packet
  public InetAddress dstIPAddr;  //destination ip adddress to which the route is sought
  public int dstSeqNum;          //destination sequence number
  public InetAddress srcIPAddr;  //source address from where the route is sought
  public int srcSeqNum;          //source sequence number
  static int tmpID = 0;          //static int to generate the unique flood ID

  private byte RREQ_ = (byte)1;

  //default constructor
  public RREQPacket() {
    type = RREQ_;
    flags = (short)1;
    hopCount = (byte)hopCount;
    dstSeqNum = srcSeqNum = floodID = 0;
  }

  //constructor
  public RREQPacket (byte type, short flags, byte hopCount,
                     InetAddress dstIPAddr, int dstSeqNum,
                     InetAddress srcIPAddr, int srcSeqNum) {
    this.type = type;
    this.flags = flags;
    this.hopCount = hopCount;
    this.floodID = ++tmpID;
    this.dstIPAddr = dstIPAddr;
    this.dstSeqNum = dstSeqNum;
    this.srcIPAddr = srcIPAddr;
    this.srcSeqNum = srcSeqNum;
  }

  //copy constructor
  public RREQPacket(RREQPacket rhs ) {
    this.type = rhs.type;
    this.flags = rhs.flags;
    this.hopCount = rhs.hopCount;
    this.floodID = rhs.floodID;
    this.dstIPAddr = rhs.dstIPAddr;
    this.dstSeqNum = rhs.dstSeqNum;
    this.srcIPAddr = rhs.srcIPAddr;
    this.srcSeqNum = rhs.srcSeqNum;
  }

  //this function is to encode the RREQ packet into a datagram packet.
  public static byte[] encode(RREQPacket packet) {
    ByteArrayOutputStream buf = new ByteArrayOutputStream();
    DataOutputStream out = new DataOutputStream(buf);

    try {
      out.writeByte(packet.type);
      out.writeShort(packet.flags);
      out.writeByte(packet.hopCount);
      out.writeInt(packet.floodID);
      try{
        out.write((packet.dstIPAddr).getAddress(), 0, 4);
      } catch (NullPointerException e) {
        System.out.println("the message is " + e.getMessage());
      }
      out.writeInt(packet.dstSeqNum);
      try {
        out.write(packet.srcIPAddr.getAddress(), 0, 4);
        } catch (NullPointerException e) {}
        out.writeInt(packet.srcSeqNum);
        out.writeInt(packet.srcSeqNum);
        out.flush();
    } catch (IOException ie) {
      System.out.println("IO ERROR\n");
    }
    return buf.toByteArray();
  }

  //this function decodes the datagram packet and gets the RREQ packet info
  public RREQPacket decode(DatagramPacket packet) {
    ByteArrayInputStream payload = new ByteArrayInputStream(packet.getData());
    DataInputStream src = new DataInputStream(payload);

    try {
      this.type = src.readByte();
      this.flags = src.readShort();
      this.hopCount = src.readByte();
      this.floodID = src.readInt();
      byte b[] = new byte[4];
      src.read(b, 0, 4);
      this.dstIPAddr = InetAddress.getByAddress(b);
      this.dstSeqNum = src.readInt();
      src.read(b, 0 ,4);
      this.srcIPAddr = InetAddress.getByAddress(b);
      this.srcSeqNum = src.readInt();
    } catch (IOException ie) {
      System.out.println("IO ERROR in decode\n");
    }
    return this;
  }

  //put info in displayable form
  public String toString() {
    final String EOLN = java.lang.System.getProperty("line.separator");
    String value = "type = " + type + EOLN +
                   "flags = " + flags + EOLN +
                   "hop Count = " + hopCount + EOLN +
                   "Flood ID = " + floodID + EOLN +
                   "Destination IP Address = " + dstIPAddr + EOLN +
                   "Destinatoin Sequence # = " + dstSeqNum + EOLN +
                   "Source IP Address = " + srcIPAddr + EOLN +
                   "Source Sequence # = " + srcSeqNum + EOLN;
    return value;
  }
}