Networks lab

CHENDU COLLEGE OF ENGINEERING AND
TECHNOLOGY
Zamin Endathur Madurantakam, Kancheepuram District-603311.
DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING
Signature of the staff Signature of HOD
EX.NO:1 Implementation of Stop and Wait Protocol and Sliding
Window Protocol
LAB MANUAL
CS 6411- Computer Network Lab Manual
Year / Semester: II / IV

AIM:
To write a java program to perform sliding window.
ALGORITHM:
1.Start the program.
2.Get the frame size from the user
3.To create the frame based on the user request.
4.To send frames to server from the client side.
5.If your frames reach the server it will send ACK signal to client otherwise it will
send NACK signal to client.
6.Stop the program
Program :
import java.net.*;
import java.io.*;
import java.rmi.*;
public class slidsender
{
public static void main(String a[])throws Exception
{
ServerSocket ser=new ServerSocket(10);
Socket s=ser.accept();
DataInputStream in=new DataInputStream(System.in);
DataInputStream in1=new DataInputStream(s.getInputStream());
String sbuff[]=new String[8];
PrintStream p;
int sptr=0,sws=8,nf,ano,i;
String ch;
do
{
p=new PrintStream(s.getOutputStream());
System.out.print("Enter the no. of frames : ");
nf=Integer.parseInt(in.readLine());
p.println(nf);
if(nf<=sws-1)
{
System.out.println("Enter "+nf+" Messages to be sendn");
for(i=1;i<=nf;i++)
{
sbuff[sptr]=in.readLine();

p.println(sbuff[sptr]);
sptr=++sptr%8;
}
sws-=nf;
System.out.print("Acknowledgment received");
ano=Integer.parseInt(in1.readLine());
System.out.println(" for "+ano+" frames");
sws+=nf;
}
else
{
System.out.println("The no. of frames exceeds window size");
break;
}
System.out.print("nDo you wants to send some more frames : ");
ch=in.readLine(); p.println(ch);
}
while(ch.equals("yes"));
s.close();
}
}
RECEIVER PROGRAM
import java.net.*;
import java.io.*;
class slidreceiver
{
public static void main(String a[])throws Exception
{
Socket s=new Socket(InetAddress.getLocalHost(),10);
DataInputStream in=new DataInputStream(s.getInputStream());
PrintStream p=new PrintStream(s.getOutputStream());
int i=0,rptr=-1,nf,rws=8;
String rbuf[]=new String[8];
String ch; System.out.println();
do
{
nf=Integer.parseInt(in.readLine());
if(nf<=rws-1)
{

for(i=1;i<=nf;i++)
{
rptr=++rptr%8;
rbuf[rptr]=in.readLine();
System.out.println("The received Frame " +rptr+" is : "+rbuf[rptr]);
}
rws-=nf;
System.out.println("nAcknowledgment sentn");
p.println(rptr+1); rws+=nf; }
else
break;
ch=in.readLine();
}
while(ch.equals("yes"));
}
}
OUTPUT:
//SENDER OUTPUT
Enter the no. of frames : 4
Enter 4 Messages to be send
hiii
how r u
i am fine
how is evryone
Acknowledgment received for 4 frames
Do you wants to send some more frames : no
//RECEIVER OUTPUT
The received Frame 0 is : hiii
The received Frame 1 is : how r u
The received Frame 2 is : i am fine
The received Frame 3 is : how is everyone
EX.NO:2 Study of Socket Programming and Client – Server model

AIM:
To implement socket programming date and time display from client to server using TCP
Sockets
ALGORITHM:
Server
1. Create a server socket and bind it to port.
2. Listen for new connection and when a connection arrives, accept it.
3. Send server‟s date and time to the client.
4. Read client‟s IP address sent by the client.
5. Display the client details.
6. Repeat steps 2-5 until the server is terminated.
7. Close all streams.
8. Close the server socket.
9. Stop.
Client
1. Create a client socket and connect it to the server‟s port number.
2. Retrieve its own IP address using built-in function.
3. Send its address to the server.
4. Display the date & time sent by the server.
5. Close the input and output streams.
6. Close the client socket.
7. Stop.
PROGRAM:
//TCP Date Server--tcpdateserver.java
import java.net.*;
import java.io.*;
import java.util.*;
class tcpdateserver
{
public static void main(String arg[])
{
ServerSocket ss = null;
Socket cs; PrintStream ps;
BufferedReader dis;
String inet; try
{
ss = new ServerSocket(4444);
System.out.println("Press Ctrl+C to quit"); while(true)
{
cs = ss.accept();
ps = new PrintStream(cs.getOutputStream());

Date d = new Date()
ps.println(d);
dis = new BufferedReader(new InputStreamReader(cs.getInputStream()));
inet = dis.readLine(); System.out.println("Client System/IP address is :"+ inet);
ps.close(); dis.close();
}
}
catch(IOException e)
{ System.out.println("The exception is :" + e);
}
}
}
// TCP Date Client--tcpdateclient.java
import java.net.*;
import java.io.*;
class tcpdateclient
{
public static void main (String args[])
{ Socket soc; BufferedReader dis;
String sdate; PrintStream ps;
try { InetAddress ia = InetAddress.getLocalHost();
if (args.length == 0)
soc = new Socket(InetAddress.getLocalHost(),4444);
else soc = new Socket(InetAddress.getByName(args[0]),4444);
dis = new BufferedReader(new InputStreamReader(soc.getInputStream()));
sdate=dis.readLine(); System.out.println("The date/time on server is : " +sdate);
ps = new PrintStream(soc.getOutputStream());
ps.println(ia);
ps.close();
{
System.out.println("THE EXCEPTION is :" + e);
}
}
}
OUTPUT
Server:
$ javac tcpdateserver.java $
java tcpdateserver
Press Ctrl+C to quit Client System/IP address is : localhost.localdomain/127.0.0.1 Client
System/IP address is : localhost.localdomain/127.0.0.1

Client: $
javac tcpdateclient.java $ java tcpdateclient The date/time on server is: Wed Jul 06 07:12:03
GMT 2011
Every time when a client connects to the server, server‟s date/time will be returned to the
client for synchronization.
RESULT:
Thus the program for implementing to display date and time from client to server using
TCP Sockets was executed successfully and output verified using various samples.
EX.NO:3 Write a code simulating ARP /RARP protocols.

Aim:
To write a java program for simulating arp/rarp protocols
ALGORITHM:
server
1. Create a server socket and bind it to port.
2. Listen for new connection and when a connection arrives, accept it.
3. Send server‟s date and time to the client.
4. Read client‟s IP address sent by the client.
5. Display the client details.
6. Repeat steps 2-5 until the server is terminated.
7. Close all streams.
8. Close the server socket.
9. Stop.
Client
1. Create a client socket and connect it to the server‟s port number.
2. Retrieve its own IP address using built-in function.
3. Send its address to the server.
4. Display the date & time sent by the server.
5. Close the input and output streams.
6. Close the client socket.
7. Stop.
Program
Program for Address Resolutuion Protocol (ARP) using TCP
Client:
import java.io.*;
import java.net.*;
import java.util.*;
class Clientarp
{
public static void main(String args[])
{
try

{
BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
Socket clsct=new Socket("127.0.0.1",139);
DataInputStream din=new DataInputStream(clsct.getInputStream());
DataOutputStream dout=new DataOutputStream(clsct.getOutputStream());
System.out.println("Enter the Logical address(IP):");
String str1=in.readLine();
dout.writeBytes(str1+'n');
String str=din.readLine();
System.out.println("The Physical Address is: "+str);
clsct.close();
}
catch (Exception e)
{
System.out.println(e);
}
}
}
Server:
import java.io.*;
import java.net.*;
import java.util.*;
class Serverarp
{
{
try
{
ServerSocket obj=new ServerSocket(139);
Socket obj1=obj.accept();
while(true)
{
DataInputStream din=new DataInputStream(obj1.getInputStream());
DataOutputStream dout=new DataOutputStream(obj1.getOutputStream());
String ip[]={"165.165.80.80","165.165.79.1"};
String mac[]={"6A:08:AA:C2","8A:BC:E3:FA"};
for(int i=0;i<ip.length;i++)
{

if(str.equals(ip[i]))
{
dout.writeBytes(mac[i]+'n');
break;
}
}
obj.close();
}
}
catch(Exception e)
{
}
}
}
Output:
E:networks>java Serverarp
E:networks>java Clientarp
Enter the Logical address(IP):
165.165.80.80
The Physical Address is: 6A:08:AA:C2
Program for Reverse Address Resolutuion Protocol (RARP) using UDP
Client:
import java.io.*;
import java.net.*;
import java.util.*;
class Clientrarp12
{
{
try
{
DatagramSocket client=new DatagramSocket();
InetAddress addr=InetAddress.getByName("127.0.0.1");
byte[] sendbyte=new byte[1024];
byte[] receivebyte=new byte[1024];
System.out.println("Enter the Physical address (MAC):");

String str=in.readLine();
sendbyte=str.getBytes();
DatagramPacket sender=new
DatagramPacket(sendbyte,sendbyte.length,addr,1309);
client.send(sender);
DatagramPacket receiver=new DatagramPacket(receivebyte,receivebyte.length);
client.receive(receiver);
String s=new String(receiver.getData());
System.out.println("The Logical Address is(IP): "+s.trim());
client.close();
}
catch(Exception e)
{
}
}
}
Server:
import java.io.*;
import java.net.*;
import java.util.*;
class Serverrarp12
{
{
try
{
DatagramSocket server=new DatagramSocket(1309);
while(true)
{
byte[] sendbyte=new byte[1024];
byte[] receivebyte=new byte[1024];
DatagramPacket receiver=new
DatagramPacket(receivebyte,receivebyte.length);
server.receive(receiver);
String str=new String(receiver.getData());
String s=str.trim();
//System.out.println(s);
InetAddress addr=receiver.getAddress();
int port=receiver.getPort();

String ip[]={"165.165.80.80","165.165.79.1"};
String mac[]={"6A:08:AA:C2","8A:BC:E3:FA"};
for(int i=0;i<ip.length;i++)
{
if(s.equals(mac[i]))
{
sendbyte=ip[i].getBytes();
DatagramPacket sender=new
DatagramPacket(sendbyte,sendbyte.length,addr,port);
server.send(sender);
break;
}
}
break;
}
}
catch(Exception e)
{
}
}
}
Output:
I:ex>java Serverrarp12
I:ex>java Clientrarp12
Enter the Physical address (MAC):
6A:08:AA:C2
The Logical Address is(IP): 165.165.80.80
Result :
Thus the program for implementing to display simulating ARP /RARP protocols.

EX-NO. 4. Write a code simulating PING and TRACEROUTE commands
Aim:
To Write The java program for simulating ping and traceroute commands
ALGORITHM:
6.Stop the program
Program
//pingclient.java
import java.io.*;
import java.net.*;
import java.util.Calendar;
class pingclient
{
public static void main(String args[])throws Exception
{
String str;
int c=0;
long t1,t2;
Socket s=new Socket("127.0.0.1",5555);
DataInputStream dis=new DataInputStream(s.getInputStream());
PrintStream out=new PrintStream(s.getOutputStream());
while(c<4)
{
t1=System.currentTimeMillis();
str="Welcome to network programming world";
out.println(str);
System.out.println(dis.readLine());
t2=System.currentTimeMillis();
System.out.println(";TTL="+(t2-t1)+"ms");
c++;
}
s.close();

}
}
//pingserver.java
import java.io.*;
import java.net.*;
import java.util.*;
import java.text.*;
class pingserver
{
{
ServerSocket ss=new ServerSocket(5555);
Socket s=ss.accept();
int c=0;
while(c<4)
{
DataInputStream dis=new DataInputStream(s.getInputStream());
PrintStream out=new PrintStream(s.getOutputStream());
String str=dis.readLine();
out.println("Reply from"+InetAddress.getLocalHost()+";Length"+str.length());
c++;
}
s.close();
}
}
Out put :
Result:
Thus the program was implementing to simulating ping and traceroute commands

5. Create a socket for HTTP for web page upload and download.
Aim:
To write a java program for socket for HTTP for web page upload and download .
Algorithm
6.Stop the program
Program :
import javax.swing.*;
import java.net.*;
import java.awt.image.*;
import javax.imageio.*;
import java.io.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
public class Client{
public static void main(String args[]) throws Exception{
Socket soc;
BufferedImage img = null;
soc=new Socket("localhost",4000);
System.out.println("Client is running. ");
try {
System.out.println("Reading image from disk. ");
img = ImageIO.read(new File("digital_image_processing.jpg"));
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(img, "jpg", baos);
baos.flush();
byte[] bytes = baos.toByteArray();
baos.close();

System.out.println("Sending image to server. ");
OutputStream out = soc.getOutputStream();
DataOutputStream dos = new DataOutputStream(out);
dos.writeInt(bytes.length);
dos.write(bytes, 0, bytes.length);
System.out.println("Image sent to server. ");
dos.close();
out.close();
}catch (Exception e) {
System.out.println("Exception: " + e.getMessage());
soc.close();
}
soc.close();
}
}
import java.net.*;
import java.io.*;
import java.awt.image.*;
import javax.imageio.*;
import javax.swing.*;
class Server {
public static void main(String args[]) throws Exception{
ServerSocket server=null;
Socket socket;
server=new ServerSocket(4000);
System.out.println("Server Waiting for image");
socket=server.accept();
System.out.println("Client connected.");
InputStream in = socket.getInputStream();
DataInputStream dis = new DataInputStream(in);
int len = dis.readInt();
System.out.println("Image Size: " + len/1024 + "KB");
byte[] data = new byte[len];
dis.readFully(data);
dis.close();
in.close();
InputStream ian = new ByteArrayInputStream(data);
BufferedImage bImage = ImageIO.read(ian);
JFrame f = new JFrame("Server");
ImageIcon icon = new ImageIcon(bImage);
JLabel l = new JLabel();

l.setIcon(icon);
f.add(l);
f.pack();
f.setVisible(true);
}
}
Output
When you run the client code, following output screen would appear on client side.
RESULT
Thus the program was implementing to socket for HTTP for web page upload and
download.

EX-NO 6. Write a program to implement RPC (Remote Procedure Call)
Aim:
To write a java program to implement RPC (remote procedure call
Algorithm :
6.Stop the program
Program:
RPC PROGRAM
Client
import java.io.*;
import java.net.*;
import java.util.*;
class Clientrpc
{
{
try
{
System.out.println("Enter String");
dout.writeBytes(str+'n');
clsct.close();
}
catch (Exception e)
{
}
}
}
Server
import java.io.*;
import java.net.*;

import java.util.*;
class Serverrpc
{
{
try
{
while(true)
{
Process p=Runtime.getRuntime().exec(str);
}
}
catch(Exception e)
{
}
}
}
OUTPUT
Server
Y:networksremote>java Serverrpc
Client
Y:networksremote>java Clientrpc
Enter String
calc
Result :
Thus the program was implementing to implement RPC (remote procedure call

EX-NO 7. Implementation of Subnetting
Aim:
Write a program to implement subnetting and find the subnet masks.
Algorithm :
6.Stop the program
Program
import java.util.Scanner;
class Subnet
{
{
Scanner sc = new Scanner(System.in);
System.out.print(―Enter the ip address: ―);
String ip = sc.nextLine();
String split_ip[] = ip.split(―.‖);
//SPlit the string after every .
String split_bip[] = new String[4];
//split binary ip
String bip = ―‖;
for(int i=0;i<4;i++){
split_bip[i] = appendZeros(Integer.toBinaryString(Integer.parseInt(split_ip[i])));
// ―18‖ => 18 => 10010 => 00010010
bip += split_bip[i];
}
System.out.println(―IP in binary is ―+bip);
System.out.print(―Enter the number of addresses: ―);
int n = sc.nextInt();

//Calculation of mask
int bits = (int)Math.ceil(Math.log(n)/Math.log(2)); /*eg if address = 120, log 120/log 2 gives log
to the base 2 => 6.9068, ceil gives us upper integer */
System.out.println(―Number of bits required for address = ―+bits);
int mask = 32-bits;
System.out.println(―The subnet mask is = ―+mask);
//Calculation of first address and last address
int fbip[] = new int[32];
for(int i=0; i<32;i++) fbip[i] = (int)bip.charAt(i)-48; //convert cahracter 0,1 to integer 0,1
for(int i=31;i>31-bits;i–)//Get first address by ANDing last n bits with 0
fbip[i] &= 0;
String fip[] = {―‖,‖‖,‖‖,‖‖};
for(int i=0;i<32;i++)
fip[i/8] = new String(fip[i/8]+fbip[i]);
System.out.print(―First address is = ―);
System.out.print(Integer.parseInt(fip[i],2));
if(i!=3) System.out.print(―.‖);
}
System.out.println();
int lbip[] = new int[32];
for(int i=0; i<32;i++) lbip[i] = (int)bip.charAt(i)-48; //convert cahracter 0,1 to integer 0,1
for(int i=31;i>31-bits;i–)//Get last address by ORing last n bits with 1
lbip[i] |= 1;
String lip[] = {―‖,‖‖,‖‖,‖‖};
for(int i=0;i<32;i++)
lip[i/8] = new String(lip[i/8]+lbip[i]);
System.out.print(―Last address is = ―);
System.out.print(Integer.parseInt(lip[i],2));
if(i!=3) System.out.print(―.‖);
}
System.out.println();
}
static String appendZeros(String s){
String temp = new String(―00000000″);
return temp.substring(s.length())+ s;
}
}

Output
Enter the ip address: 100.110.150.10
IP in binary is 01100100011011101001011000001010
Enter the number of addresses: 7
Number of bits required for address = 3
The subnet mask is = 29
First address is = 100.110.150.8
Last address is = 100.110.150.15
Result :
Thus the Program was displayed implement subnetting and find the subnet masks.

EX-NO 8. Applications using TCP Sockets like
a. Echo client and echo server
Aim
To write a java program for appalaction using TCP Sockets Links
Algorithm
6.Stop the program
Program :
/echo client.java
import java.io.*;
import java.net.*;
import java.util.*;
public class echoclient
{
{
Socket c=null;
DataInputStream usr_inp=null;
DataInputStream din=new DataInputStream(System.in);
DataOutputStream dout=null;
try
{
c=new Socket("127.0.0.1",5678);
usr_inp=new DataInputStream(c.getInputStream());
dout=new DataOutputStream(c.getOutputStream());
}
{
}

if(c!=null || usr_inp!=null || dout!=null)
{
String unip;
while((unip=din.readLine())!=null)
{
dout.writeBytes(""+unip);
dout.writeBytes("n");
System.out.println("n the echoed message");
System.out.println(usr_inp.readLine());
System.out.println("n enter your message");
}
System.exit(0);
}
din.close();
usr_inp.close();
c.close();
}
}
//echoserver.java
import java.io.*;
import java.net.*;
public class echoserver
{
{
ServerSocket m=null;
Socket c=null;
try
{
m=new ServerSocket(5678);
c=m.accept();
}
{}
if(c!=null || usr_inp!=null)

{
String unip;
while(true)
{
System.out.println("nMessage from Client...");
String m1=(usr_inp.readLine());
System.out.println(m1);
dout.writeBytes(""+m1);
}
}
dout.close();
usr_inp.close();
c.close();
}
}
Output :
b. Chat
/talkclient.java
import java.io.*;
import java.net.*;
public class talkclient
{
{
Socket c=null;
try

{
c=new Socket("127.0.0.1",1234);
}
{}
if(c!=null || usr_inp!=null || dout!=null)
{
String unip;
System.out.println("nEnter the message for server:");
while((unip=din.readLine())!=null)
{
System.out.println("reply");
System.out.println(usr_inp.readLine());
System.out.println("n enter your message:");
}
System.exit(0);
}
din.close();
usr_inp.close();
c.close();
}
}
//talkserver.java
import java.io.*;
import java.net.*;
public class talkserver
{
{
ServerSocket m=null;
Socket c=null;
try
{

m=new ServerSocket(1234);
c=m.accept();
}
{}
if(c!=null||usr_inp!=null)
{
String unip;
while(true)
{
System.out.println("nmessage from client:");
String m1=usr_inp.readLine();
System.out.println(m1);
System.out.println("enter your message:");
unip=din.readLine();
}
}
dout.close();
usr_inp.close();
c.close();
}
}
OUTPUT:

C. File Transfer
Program
File Client
import java.io.*;
import java.net.*;
import java.util.*;
class Clientfile
{ public static void main(String args[])
{
Try
{
System.out.println("Enter the file name:");
System.out.println("Enter the new file name:");
String str1,ss;
FileWriter f=new FileWriter(str2);
char buffer[];
while(true)
{ str1=din.readLine();
if(str1.equals("-1")) break;
System.out.println(str1);
buffer=new char[str1.length()];
str1.getChars(0,str1.length(),buffer,0);
f.write(buffer);
}
f.close();
clsct.close();
}
catch (Exception e)
{

}
}
}
Server
import java.io.*;
import java.net.*;
import java.util.*;
class Serverfile
{
Try
{
while(true)
{
FileReader f=new FileReader(str);
BufferedReader b=new BufferedReader(f);
String s;
while((s=b.readLine())!=null)
{ System.out.println(s);
dout.writeBytes(s+'n');
}
f.close();
dout.writeBytes("-1n");
} }
catch(Exception e)
{ System.out.println(e);}
}
}

Output
File content
Computer networks
jhfcgsauf
jbsdava
jbvuesagv
client
Enter the file name:
sample.txt
server
Computer networks
jhfcgsauf
jbsdava
jbvuesagv
client
Enter the new file name:
net.txt
Computer networks
jhfcgsauf
jbsdava
jbvuesagv
Destination file
Computer networks
jhfcgsauf
jbsdava
jbvuesagv

EX-NO 9. Applications using TCP and UDP Sockets like DNS, SNMP and File
Transfer
a.DNS
Aim
To write a java program for Dns application program
Algorithm
6.Stop the program
Program
/ UDP DNS Server
Udpdnsserver
.java import java.io.*;
import java.net.*;
public class udpdnsserver
{
private static int indexOf(String[] array, String str)
{
str = str.trim();
for (int i=0; i < array.length; i++)
{
if (array[i].equals(str)) return i;
}
return -1;
}
public static void main(String arg[])throws IOException
{
String[] hosts = {"yahoo.com", "gmail.com","cricinfo.com", "facebook.com"};
String[] ip = {"68.180.206.184", "209.85.148.19","80.168.92.140", "69.63.189.16"};
System.out.println("Press Ctrl + C to Quit");
while (true)

{
DatagramSocket serversocket=new DatagramSocket(1362);
byte[] senddata = new byte[1021];
byte[] receivedata = new byte[1021];
DatagramPacket recvpack = new DatagramPacket
(receivedata, receivedata.length);
serversocket.receive(recvpack);
String sen = new String(recvpack.getData());
InetAddress ipaddress = recvpack.getAddress();
int port = recvpack.getPort();
String capsent;
System.out.println("Request for host " + sen);
if(indexOf (hosts, sen) != -1)
capsent = ip[indexOf (hosts, sen)];
else capsent = "Host Not Found";
senddata = capsent.getBytes();
DatagramPacket pack = new DatagramPacket
(senddata, senddata.length,ipaddress,port);
serversocket.send(pack);
serversocket.close();
}
}
}
//UDP DNS Client –
Udpdnsclient
.java import java.io.*;
import java.net.*;
public class udpdnsclient
{
public static void main(String args[])throws IOException
{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientsocket = new DatagramSocket();
InetAddress ipaddress;
if (args.length == 0)
ipaddress = InetAddress.getLocalHost();
else
ipaddress = InetAddress.getByName(args[0]);
byte[] senddata = new byte[1024];

byte[] receivedata = new byte[1024];
int portaddr = 1362;
System.out.print("Enter the hostname : ");
String sentence = br.readLine();
Senddata = sentence.getBytes();
DatagramPacket pack = new DatagramPacket(senddata,senddata.length, ipaddress,portaddr);
clientsocket.send(pack);
DatagramPacket recvpack =new DatagramPacket(receivedata,receivedata.length);
clientsocket.receive(recvpack);
String modified = new String(recvpack.getData());
System.out.println("IP Address: " + modified);
clientsocket.close();
}
}
OUTPUT
Server
$ javac udpdnsserver.java $ java udpdnsserver Press Ctrl + C to Quit Request for host
yahoo.com Request for host cricinfo.com Request for host youtube.com
Client
$ javac udpdnsclient.java $ java udpdnsclient Enter the hostname : yahoo.com IP Address:
68.180.206.184 $ java udpdnsclient Enter the hostname : cricinfo.com IP Address:
80.168.92.140 $ java udpdnsclient Enter the hostname : youtube.com IP Address: Host Not
Found

b. SNMP
Aim
To write a java program for SNMP application program
Algorithm
6.Stop the program
Program
import java.io.IOException;
import org.snmp4j.CommunityTarget;
import org.snmp4j.PDU;
import org.snmp4j.Snmp;
import org.snmp4j.Target;
import org.snmp4j.TransportMapping;
import org.snmp4j.event.ResponseEvent;
import org.snmp4j.mp.SnmpConstants;
import org.snmp4j.smi.Address;
import org.snmp4j.smi.GenericAddress;
import org.snmp4j.smi.OID;
import org.snmp4j.smi.OctetString;
import org.snmp4j.smi.VariableBinding;
import org.snmp4j.transport.DefaultUdpTransportMapping;
public class SNMPManager {
Snmp snmp = null;
String address = null;
* Constructor
* @param
add
*/

public SNMPManager(String add)
{
address = add;
public static void main(String[] args) throws IOException {
/**
* Port 161 is used for Read and Other operations
* Port 162 is used for the trap generation
*/
SNMPManager client = new SNMPManager("udp:127.0.0.1/161");
client.start();
/**
* OID - .1.3.6.1.2.1.1.1.0 => SysDec
* OID - .1.3.6.1.2.1.1.5.0 => SysName
* => MIB explorer will be usefull here, as discussed in previous article
*/
String sysDescr = client.getAsString(new OID(".1.3.6.1.2.1.1.1.0"));
System.out.println(sysDescr);
}
/**
* get any answers because the communication is asynchronous
* and the listen() method listens for answers.
* @throws IOException
*/
private void start() throws IOException {
TransportMapping transport = new DefaultUdpTransportMapping();
snmp = new
Snmp(transport);
// Do not forget this line!
transport.listen();
}
/**
* Method which takes a single OID and returns the response from the agent as a String.
* @param oid
* @return
*/
public String getAsString(OID oid) throws IOException {

ResponseEvent event = get(new OID[] { oid });
return event.getResponse().get(0).getVariable().toString();
}
/**
* This method is capable of handling multiple OIDs
* @param oids
* @return
*/
public ResponseEvent get(OID oids[]) throws IOException {
PDU pdu = new PDU();
for (OID oid : oids) {
pdu.add(new VariableBinding(oid));
}
pdu.setType(PDU.GET);
ResponseEvent event = snmp.send(pdu, getTarget(), null);
if(event != null) {
return event;
}
throw new RuntimeException("GET timed out");
}
/**
* This method returns a Target, which contains information about
* where the data should be fetched and how.
* @return
*/
private Target getTarget() {
Address targetAddress = GenericAddress.parse(address);
CommunityTarget target = new CommunityTarget();
target.setCommunity(new OctetString("public"));
target.setAddress(targetAddress);
target.setRetries(2);
target.setTimeout(1500);
target.setVersion(SnmpConstants.version2c);
return target;
}
}

OUT PUT
Hardware: x86 Family 6 Model 23 Stepping 10 AT/AT COMPATIBLE – Software: Windows
2000 Version 5.1 (Build 2600 Multiprocessor Free)
RESULT
Thus the SNMP program was displayed.
c. File Transfer
AIM
To write a java program for applaction using TCP and UDP Sockets Liks
Program
File Client
import java.io.*;
import java.net.*;
import java.util.*;
class Clientfile
{
Try
{
System.out.println("Enter the file name:");
System.out.println("Enter the new file name:");
String str1,ss;
FileWriter f=new FileWriter(str2);
char buffer[];
while(true)
{ str1=din.readLine();
if(str1.equals("-1")) break;
System.out.println(str1);
buffer=new char[str1.length()];
str1.getChars(0,str1.length(),buffer,0);
f.write(buffer);

}
f.close();
clsct.close();
}
catch (Exception e)
{
}
}
}
Server
import java.io.*;
import java.net.*;
import java.util.*;
class Serverfile
{
Try
{
while(true)
{
FileReader f=new FileReader(str);
BufferedReader b=new BufferedReader(f);
String s;
while((s=b.readLine())!=null)
{ System.out.println(s);
dout.writeBytes(s+'n');
}
f.close();
dout.writeBytes("-1n");
} }
catch(Exception e)
{ System.out.println(e);}
}
}

Output
File content
Computer networks
jhfcgsauf
jbsdava
jbvuesagv
client
Enter the file name:
sample.txt
server
Computer networks
jhfcgsauf
jbsdava
jbvuesagv
client
Enter the new file name:
net.txt
Computer networks
jhfcgsauf
jbsdava
jbvuesagv
Destination file
Computer networks
jhfcgsauf
jbsdava
jbvuesagv
Result
Thus the program was displayed application using file transfer

EX-NO 10. Study of Network simulator (NS).and Simulation of Congestion
Control Algorithms using NS
Aim:
To Study of Network simulator (NS).and Simulation of Congestion Control Algorithms using
NS
NET WORK SIMULATOR (NS2)
Ns overview
 Ns programming: A Quick start
 Case study I: A simple Wireless network
 Case study II: Create a new agent in Ns
Ns overview
 Ns Status
 Periodical release (ns-2.26, Feb 2003)
 Platform support
 FreeBSD, Linux, Solaris, Windows and Mac
Ns unctionalities
Routing, Transportation, Traffic sources,Queuing
disciplines, QoS
Wireless
Ad hoc routing, mobile IP, sensor-MAC
Tracing, visualization and various utilitie
NS(Network Simulators)
Most of the commercial simulators are GUI driven, while some network simulators are
CLI driven. The network model / configuration describes the state of the network (nodes,routers,
switches, links) and the events (data transmissions, packet error etc.). An important output of
simulations are the trace files. Trace files log every packet, every event that occurred in the
simulation and are used for analysis. Network simulators can also provide other tools to facilitate
visual analysis of trends and potential trouble spots.
Most network simulators use discrete event simulation, in which a list of pending
"events" is stored, and those events are processed in order, with some events triggering future
events—such as the event of the arrival of a packet at one node triggering the event of the arrival
of that packet at a downstream node.
Simulation of networks is a very complex task. For example, if congestion is high, then
estimation of the average occupancy is challenging because of high variance. To estimate the
likelihood of a buffer overflow in a network, the time required for an accurate answer can be
extremely large. Specialized techniques such as "control variates" and "importance sampling"
have been developed to speed simulation.

Examples of network simulators
There are many both free/open-source and proprietary network simulators. Examples of
notable network simulation software are, ordered after how often they are mentioned in research
papers:
1. ns (open source)
2. OPNET (proprietary software)
3. NetSim (proprietary software)
Uses of network simulators
Network simulators serve a variety of needs. Compared to the cost and time involved in setting
up an entire test bed containing multiple networked computers, routers and data links, network
simulators are relatively fast and inexpensive. They allow engineers, researchers to test scenarios
that might be particularly difficult or expensive to emulate using real hardware - for instance,
simulating a scenario with several nodes or experimenting with a new protocol in the network.
Network simulators are particularly useful in allowing researchers to test new networking
protocols or changes to existing protocols in a controlled and reproducible environment. A
typical network simulator encompasses a wide range of networking technologies and can help
the users to build complex networks from basic building blocks such as a variety of nodes and
links. With the help of simulators, one can design hierarchical networks using various types of
nodes like computers, hubs, bridges, routers, switches, links, mobile units etc.
Various types of Wide Area Network (WAN) technologies like TCP, ATM, IP etc. and Local
Area Network (LAN) technologies like Ethernet, token rings etc., can all be simulated with a
typical simulator and the user can test, analyze various standard results apart from devising some
novel protocol or strategy for routing etc. Network simulators are also widely used to simulate
battlefield networks in Network-centric warfare
There are a wide variety of network simulators, ranging from the very simple to the very
complex. Minimally, a network simulator must enable a user to represent a network topology,
specifying the nodes on the network, the links between those nodes and the traffic between the
nodes. More complicated systems may allow the user to specify everything about the protocols
used to handle traffic in a network. Graphical applications allow users to easily visualize the
workings of their simulated environment. Text-based applications may provide a less intuitive
interface, but may permit more advanced forms of customization.
Packet loss
occurs when one or morepacketsof data travelling across a computer networkfail to reachtheir
destination. Packet loss is distinguished as one of the three main error types encountered in
digital communications; the other two being bit errorand spurious packets caused due to noise.
Packets can be lost in a network because they may be dropped when a queue in the network node
overflows. The amount of packet loss during the steady state is another important property of a
congestion control scheme. The larger the value of packet loss, the more difficult it is for
transportlayer protocols to maintain high bandwidths, the sensitivity to loss of individual packets,
as well as to frequency and patterns of loss among longer packet sequences is strongly dependent
on the application itself.

Throughput
This is the main performance measure characteristic, and most widely used.
Incommunicationnetworks, such asEthernetorpacket radio, throughputor network
throughputis the average rate of successfulmessage delivery over a communication channel. The
throughput is usually measured inbitsper second (bit/s orbps), andsometimes indata packetsper
second or data packets pertime slotThis measure how soon the receiver is able to get a certain
amount of data send by the sender. It is determined as the ratio of the total data received to the
end to end delay. Throughput is an important factor which directly impacts the network
performance
Delay
Delay is the time elapsed while a packet travels from one point e.g., source premise or network
ingress to destination premise or network degrees. The larger the valueof delay, the more
difficult it is for transport layer protocols to maintain highbandwidths. We will calculate end to
end delay
Queue Length
A queuing system in networks can be described as packets arriving for service, waiting for
service if it is not immediate, and if having waited for service, leaving thesystem after being
served. Thus queue length is very important characteristic to determine that how well the active
queue management of the congestion control
algorithm has been working.
RESULT
Thus the study of Network simulator (NS2)was studied

11. Perform a case study about the different routing algorithms to select the
network path with itsoptimum and economical during data transfer.
i. Link State routing
Aim:
To study the link state routing
Link State routing
Routing is the process of selecting best paths in a network. In the past, the term routing was also
used to mean forwarding network traffic among networks. However this latter function is much
better described as simply forwarding. Routing is performed for many kinds of networks,
including the telephone network (circuit switching), electronic data networks (such as the
Internet), and transportation networks. This article is concerned primarily with routing in
electronic data networks using packet switching technology.
In packet switching networks, routing directs packet forwarding (the transit of logically
addressed network packets from their source toward their ultimate destination) through
intermediate nodes. Intermediate nodes are typically network hardware devices such as routers,
bridges, gateways, firewalls, or switches. General-purpose computers can also forward packets
and perform routing, though they are not specialized hardware and may suffer from limited
performance. The routing process usually directs forwarding on the basis of routing tables which
maintain a record of the routes to various network destinations. Thus, constructing routing tables,
which are held in the router's memory, is very important for efficient routing. Most routing
algorithms use only one network path at a time. Multipath routing techniques enable the use of
multiple alternative paths.
In case of overlapping/equal routes, the following elements are considered in order to decide
which routes get installed into the routing table (sorted by priority):
1. Prefix-Length: where longer subnet masks are preferred (independent of whether it is
within a routing protocol or over different routing protocol)
2. Metric: where a lower metric/cost is preferred (only valid within one and the same
routing protocol)
3. Administrative distance: where a lower distance is preferred (only valid between different
routing protocols)
Routing, in a more narrow sense of the term, is often contrasted with bridging in its assumption
that network addresses are structured and that similar addresses imply proximity within the
network. Structured addresses allow a single routing table entry to represent the route to a group
of devices. In large networks, structured addressing (routing, in the narrow sense) outperforms
unstructured addressing (bridging). Routing has become the dominant form of addressing on the
Internet. Bridging is still widely used within localized environments.

ii. Flooding
Flooding s a simple routing algorithm in which every incoming packet is sent through every
outgoing link except the one it arrived on.Flooding is used in bridging and in systems such as
Usenet and peer-to-peer file sharing and as part of some routing protocols, including OSPF,
DVMRP, and those used in ad-hoc wireless networks.There are generally two types of flooding
available, Uncontrolled Flooding and Controlled Flooding.Uncontrolled Flooding is the fatal law
of flooding. All nodes have neighbours and route packets indefinitely. More than two neighbours
creates a broadcast storm.
Controlled Flooding has its own two algorithms to make it reliable, SNCF (Sequence Number
Controlled Flooding) and RPF (Reverse Path Flooding). In SNCF, the node attaches its own
address and sequence number to the packet, since every node has a memory of addresses and
sequence numbers. If it receives a packet in memory, it drops it immediately while in RPF, the
node will only send the packet forward. If it is received from the next node, it sends it back to the
sender.
Algorithm
There are several variants of flooding algorithm. Most work roughly as follows:
1. Each node acts as both a transmitter and a receiver.
2. Each node tries to forward every message to every one of its neighbours except the
source node.
This results in every message eventually being delivered to all reachable parts of the network.
Algorithms may need to be more complex than this, since, in some case, precautions have to be
taken to avoid wasted duplicate deliveries and infinite loops, and to allow messages to eventually
expire from the system. A variant of flooding called selective flooding partially addresses these
issues by only sending packets to routers in the same direction. In selective flooding the routers
don't send every incoming packet on every line but only on those lines which are going
approximately in the right direction.
Advantages
 f a packet can be delivered, it will (probably multiple times).
 Since flooding naturally utilizes every path through the network, it will also use the
shortest path.
 This algorithm is very simple to implement.

Disadvantages
 Flooding can be costly in terms of wasted bandwidth. While a message may only have
one destination it has to be sent to every host. In the case of a ping flood or a denial of
service attack, it can be harmful to the reliability of a computer network.
 Messages can become duplicated in the network further increasing the load on the
networks bandwidth as well as requiring an increase in processing complexity to
disregard duplicate messages.
 Duplicate packets may circulate forever, unless certain precautions are taken:
 Use a hop count or a time to live count and include it with each packet. This value should
take into account the number of nodes that a packet may have to pass through on the way
to its destination.
 Have each node keep track of every packet seen and only forward each packet once
 Enforce a network topology without loops
iii . Distance vector
In computer communication theory relating to packet-switched networks, a distance-
vector routing protocol is one of the two major classes of routing protocols, the other major
class being the link-state protocol. Distance-vector routing protocols use the Bellman–Ford
algorithm, Ford–Fulkerson algorithm, or DUAL FSM (in the case of Cisco Systems's protocols)
to calculate paths.
A distance-vector routing protocol requires that a router informs its neighbors of topology
changes periodically. Compared to link-state protocols, which require a router to inform all the
nodes in a network of topology changes, distance-vector routing protocols have less
computational complexity and message overhead.
The term distance vector refers to the fact that the protocol manipulates vectors (arrays) of
distances to other nodes in the network. The vector distance algorithm was the original
ARPANET routing algorithm and was also used in the internet under the name of RIP (Routing
Information Protocol).
Examples of distance-vector routing protocols include RIPv1 and RIPv2 and IGRP.
Method
Routers using distance-vector protocol do not have knowledge of the entire path to a destination.
Instead they use two methods:
1. Direction in which router or exit interface a packet should be forwarded.
2. Distance from its destination
Distance-vector protocols are based on calculating the direction and distance to any link in a
network. "Direction" usually means the next hop address and the exit interface. "Distance" is a

measure of the cost to reach a certain node. The least cost route between any two nodes is the
route with minimum distance. Each node maintains a vector (table) of minimum distance to
every node. The cost of reaching a destination is calculated using various route metrics. RIP uses
the hop count of the destination whereas IGRP takes into account other information such as node
delay and available bandwidth.
Updates are performed periodically in a distance-vector protocol where all or part of a router's
routing table is sent to all its neighbors that are configured to use the same distance-vector
routing protocol. RIP supports cross-platform distance vector routing whereas IGRP is a Cisco
Systems proprietary distance vector routing protocol. Once a router has this information it is able
to amend its own routing table to reflect the changes and then inform its neighbors of the
changes. This process has been described as ‗routing by rumor‘ because routers are relying on
the information they receive from other routers and cannot determine if the information is
actually valid and true. There are a number of features which can be used to help with instability
and inaccurate routing information.
EGP and BGP are not pure distance-vector routing protocols because a distance-vector protocol
calculates routes based only on link costs whereas in BGP, for example, the local route
preference value takes priority over the link cost.
Count-to-infinity problem
The Bellman–Ford algorithm does not prevent routing loops from happening and suffers from
the count-to-infinity problem. The core of the count-to-infinity problem is that if A tells B that
it has a path somewhere, there is no way for B to know if the path has B as a part of it. To see the
problem clearly, imagine a subnet connected like A–B–C–D–E–F, and let the metric between the
routers be "number of jumps". Now suppose that A is taken offline. In the vector-update-process
B notices that the route to A, which was distance 1, is down – B does not receive the vector
update from A. The problem is, B also gets an update from C, and C is still not aware of the fact
that A is down – so it tells B that A is only two jumps from C (C to B to A), which is false. This
slowly propagates through the network until it reaches infinity (in which case the algorithm
corrects itself, due to the relaxation property of Bellman–Ford).
RESULT
Thus The Perform a case study about the different routing algorithms to select the
network path with itsoptimum and economical during data transfer. Was complicated .

Networks lab

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