1.

IMPLEMENTATION OF ERROR DETECTION AND CORRECTION TECHNIQUE

AIM:
To write a ‘C’ program to implement Error Detection and Correction Techniques.

ALGORITHM:

1. Get four bit data

PROGRAM:
#include<stdio.h>
#include<stdlib.h>
char data[5];
int encoded[8],edata[7],syndrome[3];
int hmatrix[3][7] = {
1,0,0,0,1,1,1,
0,1,0,1,0,1,1,
0,0,1,1,1,0,1
};
char gmatrix[4][8]={"0111000","1010100","1100010","1110001"};
int main(){
int i,j;
printf("\nHamming code----- Encoding\n");
printf("Enter 4 bit data : ");

scanf("%s",data);
printf("\nGenerator matrix\n");
for(i=0;i<4;i++)
printf("%s\n",gmatrix[i]);
printf("\nEncoded data ");
for(i=0;i<7;i++)
{
for(j=0;j<4;j++)
encoded[i]+=((data[j]-'0')*(gmatrix[j][i]-'0'));
encoded[i]=encoded[i]%2;
printf("%d ",encoded[i]);
}
printf("\nHamming code----- Decoding\n");
printf("Enter encoded bits as recieved : ");
for(i=0;i<7;i++)
scanf("%d",&edata[i]);
for(i=0;i<3;i++)
{
for(j=0;j<7;j++)
syndrome[i]+=(edata[j]*hmatrix[i][j]);
syndrome[i]=syndrome[i]%2;
}
for(j=0;j<7;j++)
if((syndrome[0]==hmatrix[0][j]) && (syndrome[1]==hmatrix[1][j])&&
(syndrome[2]==hmatrix[2][j]))
break;
if(j==7)
printf("\nError free\n");
else
{
printf("\nError recieved at bit number %d of data\n",j+1);

edata[j]=!edata[j];
printf("\nCorrect data should be : ");
for(i=0;i<7;i++)
printf("%d",edata[i]);
} getch();
return 0;
}
RESULT:
Thus the program for High Level Data Link was implemented successfully.
 2.a.IMPLEMENTATION OF SLIDING WINDOW PROTOCOL USING JAVA

AIM:

To write a JAVA program to simulate a sliding window protocol that uses Selective Repeat ARQ.

ALGORITHM:

SERVER:

1. Create a server socket.

2. Assume the sending window size

3. If the receiver is ready initialize sender’s frame sequence to 0

4. Get data from user

5. Send it to the receiver along with sequence number

6. Increment sequence number by 1

7. Repeat step 4-6 until all frames have been sent

8. Wait for acknowledgement

9. If all ACK have arrived then go to step 11.

10. Set sequence number to earliest outstanding frame for which there is no ACK. Go to step 4

11. Stop

CLIENT:

1. Create a socket for client

2. Indicate to sender, the readiness to accept frames

3. Initialize receiver’s expected frame sequence to 0

4. Accept the incoming frame

5. If frame’s sequence == receiver’s sequence and go to step 6.

6. Send an ACK.

7. Repeat step 3-6 until all frames are received in sequence and go to step 8.

8. Discard frame, thereby force the sender to retransmit. Go to step 3.

SENDER:

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 send\n");

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:
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 sent\n");
p.println(rptr+1); rws+=nf; }

else

break;

ch=in.readLine();

RESULT: Thus the program for sliding window protocol was implemented successfully.
2.b.IMPLEMENTATION OF STOP & WAIT PROTOCOL

AIM

To implement the stop and wait protocol using Java .

PROCEDURE

Sender

Step1: sequence „² 0

Step2: Accept new packet and assign sequence to it.

Step3: Send packet sequence with sequence number sequence.

Step4: Set timer for recently sent packets.

Step5: If error free acknowledgment from receiver and NextFrameExpected -> sequence

then sequence,NextFrameExpected.

Step6: If time out then go to step3.

Step7: Stop.

Receiver

Step1: Start.

Step2: NextFrameExpecteds 0, repeat steps 3 forever.

Step3: If error-free frame received and sequence= NextFrameExpected, then pass packet to higher

layer and NextFrameExpecteds NextFrameExpected+1(modulo 2).

Step4: Stop.

Sender.java

import java.io.*;

import java.net.*;

public class Sender{

Socket sender;

ObjectOutputStream out;
ObjectInputStream in;

String packet,ack,str, msg;

int n,i=0,sequence=0;

Sender(){}

public void run(){

try{

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

System.out.println("Waiting for Connection....");

sender = new Socket("localhost",2005);

sequence=0;

out=new ObjectOutputStream(sender.getOutputStream());

out.flush();

in=new ObjectInputStream(sender.getInputStream());

str=(String)in.readObject();

System.out.println("reciver > "+str);

System.out.println("Enter the data to send....");

packet=br.readLine();

n=packet.length();

do{

try{

if(i<n){

msg=String.valueOf(sequence);

msg=msg.concat(packet.substring(i,i+1));

}else if(i==n){

msg="end";out.writeObject(msg);break;
}out.writeObject(msg);

sequence=(sequence==0)?1:0;

out.flush();

System.out.println("data sent>"+msg);

ack=(String)in.readObject();

System.out.println("waiting for ack.....\n\n");

if(ack.equals(String.valueOf(sequence))){

i++;

System.out.println("receiver > "+" packet recieved\n\n");

}else{

System.out.println("Time out resending data....\n\n");

sequence=(sequence==0)?1:0;

}}catch(Exception e){}

}while(i<n+1);

System.out.println("All data sent. exiting.");

}catch(Exception e){}

finally{

try{

in.close();

out.close();

sender.close();

catch(Exception e){}

}}

public static void main(String args[]){

s.run();

}}

Receiver.java

import java.io.*;

import java.net.*;

public class Receiver{

ServerSocket reciever;

Socket connection=null;

ObjectOutputStream out;

ObjectInputStream in;

String packet,ack,data="";

int i=0,sequence=0;

Receiver(){}

public void run(){

try{

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

reciever = new ServerSocket(2005,10);

System.out.println("waiting for connection...");

connection=reciever.accept();

sequence=0;

System.out.println("Connection established :");

out=new ObjectOutputStream(connection.getOutputStream());

out.flush();

in=new ObjectInputStream(connection.getInputStream());
out.writeObject("connected .");

do{

try{

packet=(String)in.readObject();

if(Integer.valueOf(packet.substring(0,1))==sequence){

data+=packet.substring(1);

sequence=(sequence==0)?1:0;

System.out.println("\n\nreceiver >"+packet);

else

System.out.println("\n\nreceiver >"+packet +" duplicate data");

}if(i<3){

out.writeObject(String.valueOf(sequence));i++;

}else{

out.writeObject(String.valueOf((sequence+1)%2));

i=0;

}}

catch(Exception e){}

}while(!packet.equals("end"));

System.out.println("Data recived="+data);

out.writeObject("connection ended .");

}catch(Exception e){}

finally{

try{in.close();
out.close();

reciever.close();

catch(Exception e){}

}}

public static void main(String args[]){

Receiver s=new Receiver();

while(true){

s.run();

}
RESULT:
Thus the program is executed successfully and the output is verified.

IMPLEMENTATION OF HIGH LEVEL DATA LINK CONTROL

AIM:

To write a ‘C’ program to implement High Level Data Link Control.

ALGORITHM:

1. Initialize the variables.

2. Enter the string of bits.

3. Insert a flag value.

4. Insert a zero at the beginning and end of each flag value

PROGRAM:

#include<stdio.h>

#include<string.h>

void main()
{

int i,j,count=0,nl;

char str[100];

printf("enter the bit string:");

gets(str);

for(i=0;i<strlen(str);i++)

count=0;

for(j=i;j<=(i+5);j++)

if(str[j]=='1')

count++;

if(count==6)

nl=strlen(str)+2;

for(;nl>=(i+5);nl--)

str[nl]=str[nl-1];

str[i+5]='0';

i=i+7;

}
}

puts(str);

getch();

OUTPUT:

ENTER THE BIT STRING: 000111111001

000111110001

PING COMMAND PROGRAM USING JAVA

AIM:

To write a Java program to execute the PING command.

ALGORITHM:

1. Start the process.

2. Establish the connection between two systems

3. Get the address of the system to be pinged

4. Print the number of packets sent and received

5. Stop the process.

Program

import java.io.*;

import java.net.*;

class pingTest {

public static void main(String[] args) {

String ip = "127.0.0.1";

String pingResult = "";

String pingCmd = "ping " + ip;

try {
Runtime r = Runtime.getRuntime();

Process p = r.exec(pingCmd);

BufferedReader in = new BufferedReader(new

InputStreamReader(p.getInputStream()));

String inputLine;

while ((inputLine = in.readLine()) != null) {

System.out.println(inputLine);

pingResult += inputLine;

in.close();

} catch (IOException e) {

System.out.println(e);

Output:

Result:

Thus the PING command program was executed successfully.

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

class Traceroute
{
public static void main(String args[]){

BufferedReader in;

try{
Runtime r = Runtime.getRuntime();
Process p = r.exec("tracert www.google.com");

in = new BufferedReader(new
InputStreamReader(p.getInputStream()));

String line;

if(p==null)
System.out.println("could not connect");

while((line=in.readLine())!=null){

System.out.println(line);

//in.close();
}

}catch(IOException e){

System.out.println(e.toString());

}
}
}
Output :

Tracing route to www.google.com [74.125.28.106]

1 70 ms 55 ms 70 ms 10.228.129.13
2 87 ms 84 ms 10.228.149.14
3 82 ms 85 ms 116.202.226.145
4 95 ms 94 ms 136 ms 10.228.158.82
5 Request timed out.
6 53 ms 55 ms 59 ms 116.202.226.21
7 85 ms 74 ms 82 ms 72.14.205.145
8 76 ms 75 ms 71 ms 72.14.235.69
9 124 ms 114 ms 113 ms 216.239.63.213
10 181 ms 194 ms 159 ms 66.249.95.132
11 285 ms 247 ms 246 ms 209.85.142.51
12 288 ms 282 ms 283 ms 72.14.233.138
13 271 ms 283 ms 274 ms 64.233.174.97
14 Request timed out.
15 269 ms 273 ms 283 ms pc-in-f106.1e100.net
[74.125.28.106]

Trace complete.

NsLookUP COMMAND PROGRAM USING JAVA

import java.net.*;

import java.io.*;

public class Program

/**

* @param args the command line arguments

public static void main(String[] args) {

// TODO code application logic here

if(args.length > 0 ){ //use command line

for(int i=0; i<args.length; i++){

System.out.println(lookup(args[i]));

}else{

BufferedReader in = new BufferedReader(new InputStreamReader (System.in));

System.out.println("Enter hostname or IP addresse.Enter \"exit\" to quit");

try{

while(true){

String host = in.readLine();

if(host.equalsIgnoreCase("exit")||host.equalsIgnoreCase("quit")){

break;

System.out.println(lookup(host));

}catch(IOException e){

System.err.println(e);

} /*end main */

private static String lookup(String host){

//get the bytes of the address

try{

node = InetAddress.getByName(host);

}catch(UnknownHostException e){

return "Cannot resolve host " + host;

if(isHostname(host)){

return node.getHostAddress();

}else {

//this is an IP address

return node.getHostName();

} // end of lookup

private static boolean isHostname(String host) {

//is this a ipv6 address

if(host.indexOf(":") != -1) return false;

char[] ca = host.toCharArray();

//if we see a character that is neither a digit nor a period

//then host is probably a hostname

for(int i=0; i<ca.length; i++){

if(ca[i] != '.') return true;

//Everything was either a digit or a period

// so host looks like a ip4v address in dotted quad format

return false;

}//end ishostname

}//end nslookupcl

Output:

S:\cn>javac Program.java

S:\cn>java Program

Enter hostname or IP addresse.Enter "exit" to quit

www.google.com

216.58.197.68

exit