Please help me to complete this code please

Hi
I wonder if anybody could help me.I desprately need help

Please have a look the following code :-
import java.io.*;
import java.net.*;

class TypeConvertion
{
  //Get a short integer from two bytes with offset in the buf
  public static short getShort(byte[] buf, int offset)
  {
    int high = buf[offset] & 0xff;
    int low  = buf[offset+1] & 0xff;
    return (short)(high <<8 | low);
  }


  //Store a short integer to two bytes with offset in the buf
  public static void putShort(byte[] buf, int offset, short value)
  {
    byte low      = (byte)(value & 0xff);
    byte high     = (byte)(value>>8 & 0xff);
    buf[offset]   = high;
    buf[offset+1] = low;
    return;
  }
}


public class TFTPClient
{
   short        seqn;
   byte         outb[];
   byte         inb[];
   String       fname;  //The file name
   InetAddress  server; //sever&#8217;s IP address
   int                   sport;  //server&#8217;s port number

   DatagramPacket odp;
   DatagramPacket idp;
   DatagramSocket sock;

   TFTPClient(String sn, String sp, String fn) throws Exception
   {
      seqn   = 0;
      outb   = new byte[516];
      inb     = new byte[516];
      server = InetAddress.getByName(sn); //Get server&#8217;s IP
     
    //Convert port string to port number
     sport = Integer.parseInt(sp);
     
     fname = fn;
     idp     = new DatagramPacket(inb,inb.length);
   
    //Create Datagram Socket*/
     sock  = new DatagramSocket();

    }
      
   void SendACK() throws Exception
   {
     int index = 0;
 
    //Fill ACK opcode =0x0004 field
    TypeConversion.putShort(outb,index,(short)4);
    index + = 2;
   
    //Fill ACK SEQ field
    TypeConversion.putShort(buff,index,seqn);/*ACK SEQ*/
    index + =2;

    /*Generating ACK datagram packet*/
    /*...*/
 
 
    /*Send out the ACK datagram packet*/
    /*...*/
  }

   void SendRRQ() throws Exception
   {
    int index = 0;
      
    //Fill RRQ opcode = 0x0001 field
    TypeConversion.putShort(outb,index,(short)1);
    index + = 2;
      
    //Fill the file name field
    byte[] temp = fname.getBytes();
    for(int i = 0;i < temp.length;i++);
    outb [i + index] = temp[i];
  }
    index +      = temp.length;
    outb[index] = 0; //End of the file name
    index +       = 1;
      
    //Fill the file data mode, using octet mode
    String mode = "octet";
    temp        = mode.getBytes();

    for(int i = 0;i <temp.length; i++)
        {
        outb[i+index] = temp[i];
        }
   

     /*Fill the end indicator of the packet*/
     /*...*/
    /*Generating ACK packet*/
    /*...*/
    /*Send out the ACK packet*/
    /*...*/
}

    void getFile() throws Exception{
    /*Create a file*/
    /*...*/
    /*Using FileOutputStream to open the file*/
    /*...*/
    int opcode;
    short rseq;
    int length;
    /*Send RRQ packet*/
    /*...*/
    while(true)
      {
    /*Receive the packet to idp from the server*/
    /*...*/
   /*Get OPCODE from the packet*/
   opcode=TypeConvertion.getShort(inb,0);
   if(opcode!=0x0003){ /*DATA*/
   continue;
}
  /*Get SEQ from the packet*/
  rseq   = TypeConvertion.getShort(inb,2);
  if(rseq==seqn+1){/*it is a new packet*/
  /*We don't check the server's IP address*/
  /*Store the data into file*/
  fos.write(inb,4,length-4);
  seqn=rseq;
  /*Send ACK*/
  /*...*/
 if(length<516){/*check end of the file*/
 sock.close();
 fos.close();
 return;
}
continue;
}
if(rseq==seqn){ /*duplicated copy*/
/*Acknowledge the received packet again*/
/*...*/


continue;
}
/*error sequence, do nothing*/
}
}
public void main(String args[]) throws Exception{
if(args.length!=3){
System.out.println("Usage: TFTPClient <servername>
<port> <filename>");
return;
}
TFTPClient tftp=new TFTPClient(args[0],args[1],args[2]);
tftp.getFile();
}
}

This is a simple  TFTP client whose function is to retrive the file from the TFTP server and store in a local file.Could anybody please fill the empty parts under the comments.(/*.......*/)


Thank you