1. write a program for error detecting code using crc ... · 3 8 1 4 6 4 the routing table for node...

1. Write a program for error detecting code using CRC-CCITT (16bit)

#include<stdio.h>

char m[50],g[50],r[50],q[50],temp[50];

void caltrans(int);

void crc(int);

void calram();

void shiftl();

int main()

{

int n,i=0;

char ch,flag=0;

printf("Enter the frame bits:");

while((ch=getc(stdin))!='\n')

m[i++]=ch;

n=i;

for(i=0;i<16;i++)

m[n++]='0';

m[n]='\0';

printf("Message after appending 16 zeros:%s",m);

for(i=0;i<=16;i++)

g[i]='0';

g[0]=g[4]=g[11]=g[16]='1';g[17]='\0';

printf("\ngenerator:%s\n",g);

crc(n);

printf("\n\nquotient:%s",q);

caltrans(n);

printf("\ntransmitted frame:%s",m);

printf("\nEnter transmitted freme:");

scanf("\n%s",m);

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printf("CRC checking\n");

crc(n);

printf("\n\nlast remainder:%s",r);

for(i=0;i<16;i++)

if(r[i]!='0')

flag=1;

else

continue;

if(flag==1)

printf("Error during transmission");

else

printf("\n\nReceived freme is correct");

}

void crc(int n)

{

int i,j;

for(i=0;i<n;i++)

temp[i]=m[i];

for(i=0;i<16;i++)

r[i]=m[i];

printf("\nintermediate remainder\n");

for(i=0;i<n-16;i++)

{

if(r[0]=='1')

{

q[i]='1';

calram();

}

else

{

q[i]='0';


shiftl();

}

r[16]=m[17+i];

r[17]='\0';

printf("\nremainder %d:%s",i+1,r);

for(j=0;j<=17;j++)

temp[j]=r[j];

}

q[n-16]='\0';

}

void calram()

{

int i,j;

for(i=1;i<=16;i++)

r[i-1]=((int)temp[i]-48)^((int)g[i]-48)+48;

}

void shiftl()

{

int i;

for(i=1;i<=16;i++)

r[i-1]=r[i];

}

void caltrans(int n)

{

int i,k=0;

for(i=n-16;i<n;i++)

m[i]=((int)m[i]-48)^((int)r[k++]-48)+48;

m[i]='\0';

}


OUTPUT:-

[root@localhost nwcn]# vi 1.c

[root@localhost nwcn]# cc 1.c

[root@localhost nwcn]# ./a.out

Enter the binary data

1011

The msg before adding checksum:

10110000000000000000

The checksum calculated:

1011000101101011

The code word is:10111011000101101011

Enter the transmitted code word

10111011000101101011

Received msg:10111011000101101011

The checksum is:0000000000000000

No error in the msg



Enter the binary data

1101

The msg before adding checksum:

11010000000000000000

The checksum calculated:

1101000110101101

The code word is:11011101000110101101

Enter the transmitted code word

10111101000110101101

Received msg:10111101000110101101

The checksum is:0110000011000110

Error in the msg


PROGRAM # 2: Frame sorting technique used in buffers.

#include<stdio.h>

#include<string.h>

#define FRAM_TXT_SIZ 3

#define MAX_NOF_FRAM 127

char str[FRAM_TXT_SIZ*MAX_NOF_FRAM];

struct frame // structure maintained to hold frames

{ char text[FRAM_TXT_SIZ];

int seq_no;

}fr[MAX_NOF_FRAM], shuf_ary[MAX_NOF_FRAM];

int assign_seq_no() //function which splits message

{ int k=0,i,j; //into frames and assigns sequence no

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

{ fr[k].seq_no = k;

for(j=0; j < FRAM_TXT_SIZ && str[i]!='\0'; j++)

fr[k].text[j] = str[i++];

}

printf("\nAfter assigning sequence numbers:\n");

for(i=0; i < k; i++)

printf("%d:%s ",i,fr[i].text);

return k; //k gives no of frames

}

void generate(int *random_ary, const int limit) //generate array of random nos

{ int r, i=0, j;

while(i < limit)

{ r = random() % limit;

for(j=0; j < i; j++)

if( random_ary[j] == r )

break;

if( i==j ) random_ary[i++] = r;

} }

void shuffle( const int no_frames ) // function shuffles the frames

{

int i, k=0, random_ary[no_frames];


generate(random_ary, no_frames);

for(i=0; i < no_frames; i++)

shuf_ary[i] = fr[random_ary[i]];

printf("\n\nAFTER SHUFFLING:\n");

for(i=0; i < no_frames; i++)

printf("%d:%s ",shuf_ary[i].seq_no,shuf_ary[i].text);

}

void sort(const int no_frames) // sorts the frames

{

int i,j,flag=1;

struct frame hold;

for(i=0; i < no_frames-1 && flag==1; i++) // search for frames in sequence

{

flag=0;

for(j=0; j < no_frames-1-i; j++) //(based on seq no.) and display

if(shuf_ary[j].seq_no > shuf_ary[j+1].seq_no)

{

hold = shuf_ary[j];

shuf_ary[j] = shuf_ary[j+1];

shuf_ary[j+1] = hold;

flag=1;

}

}

}

int main()

{

int no_frames,i;

printf("Enter the message: ");

gets(str);

no_frames = assign_seq_no();

shuffle(no_frames);

sort(no_frames);

printf("\n\nAFTER SORTING\n");

for(i=0;i<no_frames;i++)

printf("%s",shuf_ary[i].text);

printf("\n\n");

} OUTPUT:


Enter the message: Welcome To Acharya Institute of Technology

After assigning sequence numbers:


0:Wel 1:com 2:e T 3:o A 4:cha 5:rya 6: In 7:sti 8:tut 9:e o 10:f T 11:ech 12:nol 13:ogy

AFTER SHUFFLING:

1:com 4:cha 9:e o 5:rya 3:o A 10:f T 2:e T 6: In 11:ech 13:ogy 0:Wel 8:tut 12:nol 7:sti

AFTER SORTING

Welcome To Acharya Institute of Technology


3. Write a program for distance vector algorithm to find suitable path for transmission

#include<stdlib.h>

#define nul 1000

#define nodes 10

int no;

struct node

{

int a[nodes][4];

}router[nodes];

void init(int r)

{

int i;

for(i=1;i<=no;i++)

{

router[r].a[i][1]=i;

router[r].a[i][2]=999;

router[r].a[i][3]=nul;

}

router[r].a[r][2]=0;

router[r].a[r][3]=r;

}

void inp(int r)

{


int i;

printf("\nEnter dist from the node %d to other nodes",r);

printf("\nPls enter 999 if there is no direct route\n",r);

for(i=1;i<=no;i++)

{

if(i!=r)

{

printf("\nEnter dist to the node %d:",i);

scanf("%d",&router[r].a[i][2]);

router[r].a[i][3]=i;

}

}

}

void display(int r)

{

int i,j;

printf("\n\nThe routing table for node %d is as follows:",r);

for(i=1;i<=no;i++)

{

if(router[r].a[i][2]>=999)

printf("\n\t\t\t %d \t no link \t no hop",router[r].a[i][1]);

else

printf("\n\t\t\t %d \t %d \t\t d",router[r].a[i][1],router[r].a[i][2],router[r].a[i][3]);

}

}

void dv_algo(int r)

{

int i,j,z;

for(i=1;i<=no;i++)


{

if(router[r].a[i][2]!=999 && router[r].a[i][2]!=0)

{

for(j=1;j<=no;j++)

{

z=router[r].a[i][2]+router[i].a[j][2];

if(router[r].a[j][2]>z)

{

router[r].a[j][2]=z;

router[r].a[j][3]=i;

}

}

}

}

}

int main()

{

int i,j,x,y;

char choice;

printf("Enter the no. of nodes required (less than 10 pls):");

scanf("%d",&no);

for(i=1;i<=no;i++)

{

init(i);

inp(i);

}

printf("\nThe configuration of the nodes after initialization is as follows:");

for(i=1;i<=no;i++)

display(i);

for(i=1;i<=no;i++)


dv_algo(i);

printf("\nThe configuration of the nodes after computation of paths is as follows:");

for(i=1;i<=no;i++)

display(i);

while(1)

{

printf("\n\nWanna continue (y/n):");

scanf("%c",&choice);

if(choice=='n')

break;

printf("\nEnter the nodes btn which shortest path is to be found:\n");

scanf("%d %d",&x,&y);

printf("\nThe length of the shortest path is %d",router[x].a[y][2]);

}

}

[root@localhost ~]# ./a.out

Enter the no. of nodes required (less than 10 pls):4

Enter dist from the node 1 to other nodes

Pls enter 999 if there is no direct route

Enter dist to the node 2:5











Enter dist to the node 1:3\

Enter dist to the node 2:








The configuration of the nodes after initialization is as follows:

The routing table for node 1 is as follows:

1 0 1

2 5 2

3 3 3

4 7 4


1 5 1

2 0 2

3 no link no hop

4 6 4


1 3 1

2 no link no hop

3 0 3

4 no link no hop



1 no link no hop

2 no link no hop

3 no link no hop

4 0 4

The configuration of the nodes after computation of paths is as follows:


1 0 1

2 5 2

3 3 3

4 7 4


1 5 1

2 0 2

3 8 1

4 6 4


1 3 1

2 8 1

3 0 3

4 10 1



1 no link no hop

2 no link no hop

3 no link no hop

4 0 4

Wanna continue (y/n):

Enter the nodes btn which shortest path is to be found:

^C

[root@localhost ~]# clear


Enter the no. of nodes required (less than 10 pls):4









The configuration of the nodes after initialization is as follows:


1 0 1

2 5 2

3 3 3

4 7 4


1 5 1

2 0 2

3 no link no hop

4 6 4


1 3 1

2 no link no hop

3 0 3


4 2 4


1 7 1

2 6 2

3 2 3

4 0 4

The configuration of the nodes after computation of paths is as follows:


1 0 1

2 5 2

3 3 3

4 5 3


1 5 1

2 0 2

3 8 1

4 6 4


1 3 1


2 8 1

3 0 3

4 2 4


1 5 3

2 6 2

3 2 3

4 0 4



1 4

The length of the shortest path is 7




4. Using TCP or IP sockets write a client/server program to make client send the name of a

file and server to send back the contents of the requested file if present.

Client Side:

#include<stdio.h>

#include<sys/types.h>

#include<sys/socket.h>

#include<netinet/in.h>

#include<netdb.h>

int main(int argc,char *argv[])

{

int sockfd,newsockfd,portno,len,n;

char buffer[256],c[20000];

struct sockaddr_in serv,cli;

FILE *fd;

if(argc<2)

{

printf("Err:no port no.\nusage:\n./client portno\n ex:./client 7777\n");

exit(1);

}

sockfd=socket(AF_INET,SOCK_STREAM,0);

bzero((char *)&serv,sizeof(serv));

portno=atoi(argv[1]);

serv.sin_family=AF_INET;

serv.sin_port=htons(portno);

if(connect(sockfd,(struct sockaddr *)&serv,sizeof(serv))<0)

{

printf("server not responding..\n\n\n\ti am to terminate\n");

exit(1);

}

printf("Enter the file with complete path\n");


scanf("%s",&buffer);

if(write(sockfd,buffer,strlen(buffer))<0)

printf("Err writing to socket..\n");

bzero(c,2000);

printf("Reading..\n..\n");

if(read(sockfd,c,1999)<0)

printf("error: read error\n");

printf("client: display content of %s\n..\n",buffer);

fputs(c,stdout);

printf("\n..\n");

return 0;

}

Server Side:

#include<stdio.h>

#include<sys/types.h>

#include<netinet/in.h>

#include<sys/socket.h>

#include<netdb.h>

int main(int argc,char *argv[])

{

int sockfd,newsockfd,portno,len,n;

char buffer[256],c[2000],cc[20000];

struct sockaddr_in serv,cli;

FILE *fd;

if(argc<2)

{

printf("erroe:no port no\n usage:\n/server port no\n");

exit(1);


}

sockfd=socket(AF_INET,SOCK_STREAM,0);

portno=atoi(argv[1]);

serv.sin_family=AF_INET;

serv.sin_addr.s_addr=INADDR_ANY;

serv.sin_port=htons(portno);

bind(sockfd,(struct sockaddr *)&serv,sizeof(serv));

listen(sockfd,10);

len=sizeof(cli);

printf("serve:\nwaiting for connection\n");

newsockfd=accept(sockfd,(struct sockaddr *)&cli,&len);

bzero(buffer,255);

n=read(newsockfd,buffer,255);

printf("\nserver recv:%s\n",buffer);

if((fd=fopen(buffer,"r"))!=NULL)

{

printf("server:%s found\n opening and reading..\n",buffer);

printf("reading..\n..reading complete");

fgets(cc,2000,fd);

while(!feof(fd))

{

fgets(c,2000,fd);

strcat(cc,c);

}

n=write(newsockfd,cc,strlen(cc));

if(n<0)

printf("error writing to socket");

printf("\ntransfer complete\n");

}

else

{


printf("server:file not found\n");

n=write(newsockfd,"file not foung",15);

if(n<0)

printf("error: writing to socket..\n");

}

return 0;

}

Output:

Server part output

[root@localhost ~]# ./a.out 4455

server online

waiting for request...

server:(null) found!

transfering the contentserver:transfer completed

Segmentation fault

[root@localhost ~]#

client part output

[root@localhost ~]# ./a.out 4455

waiting for serverserver is online

client enter the path2.c

File Recieved:Display Contents#include<stdio.h>

struct frame{

int fslno;

char data[5];

}arr[10];

sort(int n)

{

struct frame temp;

int i,j,ex;

for(i=0;i<n-1;i++)

{

for(j=0;j<n-i-1;j++)


if(arr[j].fslno>arr[j+1].fslno)

{

temp=arr[j];

ar


5. Implement the above program using as Message queue or FIFOs as IPC channels.

Server Side:

#include<stdio.h>

#include<fcntl.h>

#include<sys/stat.h>

#define fifo1 "fifo1"


int main()

{

char p[100],c[100];

int fd1,fd2,fd,i;

for(i=0;i<100;i++)

c[i]=p[i]='\0';

mknod(fifo1,S_IFIFO|0777,0);


printf("server online\n waiting for request...\n");

fd1=open(fifo1,O_RDONLY);

read(fd1,p,100);

if((fd=open(p,O_RDONLY))<0)

{

printf("\n server:file %s not found\n",p);

exit(1);

}

printf("\n server:%s found!\n transfering the content");

read(fd,c,1000);

fd2=open(fifo2,O_WRONLY);

write(fd2,c,strlen(c));

printf("server:transfer completed\n");

}


Client Side:

#include<stdio.h>

#include<fcntl.h>

#include<sys/stat.h>



int main()

{

char p[100],c[100],ch;

int fd1,fd2,fd,i;

for(i=0;i<100;i++)

c[i]=p[i]='\0';



printf("waiting for server");

fd1=open(fifo1,O_WRONLY);

printf("server is online\n client enter the path");

i=0;

while(1)

{

ch=getchar();

if(ch=='\n')

break;

p[i++]=ch;

}

p[i]='\0';

write(fd1,p,strlen(p));

if((fd=open(p,O_RDONLY))<0)

{


printf("error file not found!enter valid path name\n\n",p);

exit(1);

}

fd2=open(fifo2,O_RDONLY);

read(fd2,c,1000);

printf("File Recieved:Display Contents");

fputs(c,stdout);

printf("\n\n");

}

Output:

Server part output


server online

waiting for request...

server:(null) found!

transfering the contentserver:transfer completed

Segmentation fault

[root@localhost ~]#

client part output


waiting for serverserver is online

client enter the path2.c

File Recieved:Display Contents#include<stdio.h>

struct frame{

int fslno;

char data[5];

}arr[10];

sort(int n)

{

struct frame temp;

int i,j,ex;

for(i=0;i<n-1;i++)

{


for(j=0;j<n-i-1;j++)

if(arr[j].fslno>arr[j+1].fslno)

{

temp=arr[j];

ar


6. Write a program for simple RSA algorithm to encrypt and decrypt the data

#include<stdio.h>

#include<stdlib.h>

#include<math.h>

#include<string.h>

unsigned long modexp(unsigned long msg,unsigned long exp,unsigned long n)

{

unsigned long i,k=1;

for(i=0;i<exp;i++)

k=(k*msg)%n;

return k;

}

int main()

{

unsigned long p,q,e,d,n,z,i,C,M;

int len;

char data[100];

system("clear");

printf("Enter the value of P and Q (such that p*q>255 and p not equal to q)\n");

scanf("%lu%lu",&p,&q);

n=p*q;

z=(p-1)*(q-1);

for(i=1;i<z;i++)

{

if((z%i)==0)

continue;

else

break;


}

e=i;

printf("\nEncryption key is :%lu",e);

for(i=1;i<z;i++)

if(((e*i-1)%z)==0)

break;

d=i;

printf("\ndecryption key is :%lu",d);

printf("\npls enter the message:");

scanf("%s",data);

len=strlen(data);

for(i=0;i<len;i++)

{

M=(unsigned long)data[i];

C=modexp(M,e,n);

printf("\nencrypted value and its char representation:%lu\t%c\n",C,C);

M=modexp(C,d,n);

printf("\ndecrypted value and its char representation:%lu\t%c\n",M,M);

}

return 0;

}

Output:



Enter the value of P and Q (such that p*q>255 and p not equal to q)

31

37

Encryption key is :7

decryption key is :463

pls enter the message:computer

encrypted value and its char representation:657 �

decrypted value and its char representation:99 c

encrypted value and its char representation:629 u


decrypted value and its char representation:111 o

encrypted value and its char representation:1093 E

decrypted value and its char representation:109 m

encrypted value and its char representation:38 &

decrypted value and its char representation:112 p

encrypted value and its char representation:623 o

decrypted value and its char representation:117 u

encrypted value and its char representation:277 #

decrypted value and its char representation:116 t

encrypted value and its char representation:64 @

decrypted value and its char representation:101 e

encrypted value and its char representation:1003


decrypted value and its char representation:114 r

put:


PROGRAM # 7:- Program for hamming code generation for error detection/correction

#include<stdlib.h>

#include<stdio.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;

system("clear");

printf("Hamming Code --- Encoding\n");

printf("Enter 4 bit data : ");

scanf("%s",data);

printf("Generator Matrix\n");

for(i=0;i<4;i++)

printf("\t %s \n",gmatrix[i]);

printf("Encoded 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 received : ");

for(i=0;i<7;i++)

scanf("%d",&edata[i]);

for(i=0;i<3;i++)

{

for(j=0;j<7;j++)

syndrome[i]=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("Data is error free!!\n");

else {

printf("Error received at bit number %d of the data\n",j+1);

edata[j]=!edata[j];


printf("The Correct data Should be : ");

for(i=0;i<7;i++) printf(" %d ",edata[i]);

}

}

Output:



Hamming Code --- Encoding

Enter 4 bit data : 1001

Generator Matrix

0111000

1010100

1100010

1110001

Encoded Data : 1001001

Hamming code --- Decoding

Enter Encoded bits as received : 1

0 0 1 0 0 1

Data is error free!!



Hamming Code --- Encoding

Enter 4 bit data : 1011

Generator Matrix

0111000

1010100

1100010

1110001

Encoded Data : 0101011

Hamming code --- Decoding

Enter Encoded bits as received : 0 1 0 1 0 1 0

Error received at bit number 7 of the data

The Correct data Should be : 0 1 0 1 0 1 1


Program # 8: Program for congestion control using Leaky Bucket algorithm.

#include<stdio.h>

int rand(int a)

{ int rn=(random()%10)%a;

return rn==0?1:rn;

}

int main()

{ int packet_sz[5],i,clk,b_size,o_rate,p_sz_rm=0,p_sz,p_time;

for(i=0;i<5;++i)

packet_sz[i]=rand(6)*10;

for(i=0;i<5;++i)

printf("packet[%d]:%d bytes\t",i,packet_sz[i]);

printf("\nEnter the Output rate:");

scanf("%d",&o_rate);

printf("Enter the Bucket Size:");

scanf("%d",&b_size);

for(i=0; i<5; ++i)

{ if((packet_sz[i]+p_sz_rm) > b_size)

if(packet_sz[i] > b_size)

printf("\n\nIncomming packet size (%d) is Greater than bucket

capacity-PACKET REJECTED",packet_sz[i]);

else

printf("\n\nBucket capacity exceeded-REJECTED!!");

else

{ p_sz_rm+=packet_sz[i];

printf("\n\nIncomming Packet size: %d",packet_sz[i]);

printf("\nBytes remaining to Transmit: %d",p_sz_rm);

p_time = rand(4)*10;

printf("\nTime left for transmission: %d units",p_time);

for(clk=10; clk<=p_time; clk+=10)

{ sleep(1);

if(p_sz_rm)

{ if(p_sz_rm <= o_rate)

printf("\n Packet of size %d

Transmitted",p_sz_rm),

p_sz_rm=0;

else

printf("\n Packet of size %d Transmitted",o_rate),

p_sz_rm -= o_rate;

printf("----Bytes Remaining after Transmission:

%d",p_sz_rm);


}

else

printf("\n No packets to transmit!!");

printf(" Time Left:%d",p_time-clk);

}

}

}

}

OUTPUT:

[root@localhost nwcn]# vi 8.c



packet[0]:30 bytes packet[1]:10 bytes packet[2]:10 bytes packet[3]:50 bytes

packet[4]:30 bytes

Enter the Output rate:20

Enter the Bucket Size:50

Incomming Packet size: 30

Bytes remaining to Transmit: 30

Time left for transmission: 10 units

Packet of size 20 Transmitted----Bytes Remaining after Transmission: 10 Time Left:0





No packets to transmit!! Time Left:0





No packets to transmit!! Time Left:0





Bucket capacity exceeded-REJECTED!!


1. write a program for error detecting code using crc ... · 3 8 1 4 6 4 the routing table for node...

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