The document contains program code snippets for various networking lab programs including: 1. A CRC program to calculate and check CRC of transmitted data frames. 2. A distance vector routing program to calculate shortest paths between nodes in a network. 3. A FIFO client and server program for inter-process communication using named pipes. 4. Other programs for frame sorting, Hamming code, leaky bucket algorithm, RSA encryption, and a TCP client.

1. NETWORK LAB PROGRAMS<br />1.CRC<br />#include<stdio.h><br />#include<string.h><br />char data[100],concatdata[117],src_crc[17],dest_crc[17],frame[120],divident[18],divisor[18]=\"
10001000000100001\"
,res[17]=\"
0000000000000000\"
;<br />void crc_cal(int node)<br />{<br />int i,j;<br />for(j=17;j<=strlen(concatdata);j++)<br />{<br />if(divident[0]=='1')<br />{<br />for(i=1;i<=16;i++)<br />if(divident[i]!=divisor[i])<br />divident[i-1]='1';<br />else<br />divident[i-1]='0';<br />}<br />else<br />{<br />for(i=1;i<=16;i++)<br />divident[i-1]=divident[i];<br />}<br />if(node==0)<br />divident[i-1]=concatdata[j];<br />else<br />divident[i-1]=frame[j];<br />}<br />divident[i-1]='\0';<br />printf(\"
\ncrc is %s\n\"
,divident);<br />if(node==0)<br />{<br />strcpy(src_crc,divident);<br />}<br />else<br />strcpy(dest_crc,divident);<br />}<br />int main()<br />{<br /> int i,len,rest;<br /> printf(\"
\n\t\t\tAT SOURCE NODE\n\nenter the data to be send :\"
);<br /> gets(data);<br /> strcpy(concatdata,data);<br /> strcat(concatdata,\"
0000000000000000\"
);<br /> for(i=0;i<=16;i++)<br />divident[i]=concatdata[i];<br /> divident[i+1]='\0';<br /> crc_cal(0);<br /> printf(\"
\ndata is :\t\"
);<br /> puts(data);<br /> printf(\"
\nthe frame transmitted is :\t\"
);<br /> printf(\"
\n%s%s\"
,data,src_crc);<br /> printf(\"
\n\t\tSOURCE NODE TRANSMITTED THE FRAME ---->\"
);<br /> printf(\"
\n\n\n\n\t\t\tAT DESTINATION NODE\nenter the received frame:\t\"
);<br /> gets(frame);<br /> for(i=0;i<=16;i++)<br />divident[i]=frame[i];<br /> divident[i+1]='\0';<br /> crc_cal(1);<br /> if(strcmp(dest_crc,res)==0)<br />printf(\"
\nreceived frame is error free \"
);<br /> else<br />printf(\"
\nreceived frame has one or more error\"
);<br /> return 1;<br />}<br />2.Distance vector<br />#include<stdio.h><br />struct rtable<br />{<br />int dist[20],nextnode[20];<br />}table[20];<br />int cost[10][10],n;<br />void distvector()<br />{<br />int i,j,k,count=0;<br />for(i=0;i<n;i++)<br />{<br />for(j=0;j<n;j++)<br />{<br />table[i].dist[j]=cost[i][j];<br />table[i].nextnode[j]=j;<br />}<br />}<br /> do<br /> {<br /> count=0;<br />for(i=0;i<n;i++)<br />{<br />for(j=0;j<n;j++)<br />{<br />for(k=0;k<n;k++)<br />{<br />if(table[i].dist[j]>cost[i][k]+table[k].dist[j])<br />{<br />table[i].dist[j]=table[i].dist[k]+table[k].dist[j];<br />table[i].nextnode[j]=k;<br />count++;<br />}<br />}<br />}<br />}<br />}while(count!=0);<br />}<br />int main()<br />{<br />int i,j;<br />printf(\"
\nenter the no of vertices:\t\"
);<br />scanf(\"
%d\"
,&n);<br />printf(\"
\nenter the cost matrix\n\"
);<br />for(i=0;i<n;i++)<br />for(j=0;j<n;j++)<br />scanf(\"
%d\"
,&cost[i][j]);<br />distvector();<br />for(i=0;i<n;i++)<br />{<br />printf(\"
\nstate value for router %c \n\"
,i+65);<br />printf(\"
\ndestnode\tnextnode\tdistance\n\"
);<br />for(j=0;j<n;j++)<br />{<br />if(table[i].dist[j]==99)<br />printf(\"
%c\t\t-\t\tinfinite\n\"
,j+65);<br />else<br />printf(\"
%c\t\t%c\t\t%d\n\"
,j+65,table[i].nextnode[j]+65,table[i].dist[j]);<br />}<br />}<br />return 0;<br />}<br />3.FIFO Client<br />#include <stdio.h><br />#include <stdlib.h><br />#include <errno.h><br />#include <string.h><br />#include <fcntl.h><br />#include <sys/types.h><br />#include <sys/stat.h><br />#include <unistd.h><br />#define FIFO1_NAME \"
fifo1\"
<br />#define FIFO2_NAME \"
fifo2\"
<br />int main()<br />{<br /> char p[100],f[100],c[100];<br />int num,num2,fl,fd,fd2;<br />mknod(FIFO1_NAME,S_IFIFO | 0666, 0);<br />mknod(FIFO2_NAME,S_IFIFO | 0666,0);<br />printf(\"
\n Waiting for SERVER ! \n\n\"
);<br />fd=open(FIFO1_NAME,O_WRONLY);<br />printf(\"
Server online !\n client:Enter the path \n\"
);<br />while(gets(p), !feof(stdin))<br />{<br /> <br />if ((num = write(fd,p,strlen(p))) == -1)<br /> <br /> perror(\"
write error\n\"
);<br /> <br /> else<br /> {<br /> printf(\"
waiting for reply ...\n\"
);<br /> <br /> fd2=open(FIFO2_NAME, O_RDONLY);<br /> <br /> if ((num2=read(fd2,c,300))== -1)<br /> <br /> perror(\"
Transfer error\n\"
);<br /> <br /> else<br /> <br /> {<br /> <br /> printf(\"
File receiver ! Displaying the contents :\n\"
);<br /> <br /> if (fputs(c,stdout)== EOF)<br /> <br /> perror(\"
print error \n\"
);<br /> <br /> exit(1);<br />}<br /> }<br />}<br />}<br />4.FIFO Server<br />#include <stdio.h><br />#include <stdlib.h><br />#include <errno.h><br />#include <string.h><br />#include <fcntl.h><br />#include <sys/types.h><br />#include <sys/stat.h><br />#include <unistd.h><br />#define FIFO1_NAME \"
fifo1\"
<br />#define FIFO2_NAME \"
fifo2\"
<br />int main()<br />{<br /> <br />char p[100],f[100],c[100];<br />int num,num2,fl,fd,fd2;<br />mknod(FIFO1_NAME,S_IFIFO | 0666, 0);<br />mknod(FIFO2_NAME,S_IFIFO | 0666,0);<br />printf(\"
SERVER Online ! \n\n\"
);<br />fd=open(FIFO1_NAME,O_RDONLY);<br />printf(\"
client online !@\n waiting for request ...\n\n\"
);<br />while(1)<br />{<br /> <br />if ((num = read(fd,p,100)) == -1)<br /> <br /> perror(\"
read error\n\"
);<br /> <br /> else<br /> <br />{<br /> <br /> p[num]='\0';<br /> <br /> if (( fl=open(p,O_RDONLY)) <0)<br /> <br /> {<br /> <br /> printf(\"
\n SERVER : %s not found\n\"
);<br /> <br /> exit(1);<br /> <br /> }<br /> <br /> else<br /> <br /> {<br /> <br /> printf(\"
SERVER : %s found ! \n transfering the contents \n\"
,p);<br /> <br /> stdin=fdopen(fl,\"
r\"
);<br /> <br /> if(fgets(c,300,stdin) != NULL)<br /> <br /> {<br /> <br /> fd2=open(FIFO2_NAME, O_WRONLY);<br /> <br /> if(num2=write(fd2,c,strlen(c))== -1)<br /> perror(\"
Transfer error\n\"
);<br /> <br /> else<br /> <br /> printf(\"
SERVER : Transfer completed \n\"
);<br /> <br /> }<br /> <br /> else<br /> <br /> perror(\"
read error\n\"
);<br /> <br /> exit(1);<br /> }<br /> }<br />}<br />}<br />5.Frame<br />#include<stdio.h><br />struct frame<br />{<br />int fslno;<br />char finfo[20];<br />};<br />struct frame arr[10];<br />int n;<br />void sort()<br />{<br />int i,j,ex;<br />struct frame temp;<br />for(i=0;i<n-1;i++)<br />{<br />ex=0;<br />for(j=0;j<n-i-1;j++)<br />if(arr[j].fslno>arr[j+1].fslno)<br />{<br />temp=arr[j];<br />arr[j]=arr[j+1];<br />arr[j+1]=temp;<br />ex++;<br />}<br />}<br />}<br />int main()<br />{<br />int i;<br />system(\"
clear\"
);<br />printf(\"
enter the number of frames\n\"
);<br />scanf(\"
%d\"
,&n);<br />printf(\"
enter the frame sequence number and frame contents\n\"
);<br />for(i=0;i<n;i++)<br />scanf(\"
%d%s\"
,&arr[i].fslno,&arr[i].finfo);<br />sort();<br />printf(\"
the frames in sequence\n\"
);<br />for(i=0;i<n;i++)<br />{<br />printf(\"
01111110 %d\t%s 01111110\n\"
,arr[i].fslno,arr[i].finfo);<br />printf(\"
|---------------------------------------------|\n\"
);<br />}<br />}<br />6. Hamming code<br />#include<stdio.h><br />#include<math.h><br />main()<br />{<br />int i,j,k,count,error_pos=0,flag=0;<br />char dw[20],cw[20],data[20];<br />printf(\"
enter the data as binary bit stream 7 bits\n\"
);<br />scanf(\"
%s\"
,data);<br />for(i=1,j=0,k=0;i<12;i++)<br />{<br />if(i==(int)pow(2,j))<br />{<br />dw[i]='?'; <br />j++;<br />}<br />else<br />{<br />dw[i]=data[k];<br />k++;<br />}<br />}<br />for(i=0;i<4;i++)<br /> <br /> {<br />count=0;<br />for(j=(int)pow(2,i);j<12;j+=(int)pow(2,i))<br />{<br />for(k=0;k<(int)pow(2,i);k++)<br />{<br />if(dw[j]=='1')<br /> count++; <br />j++; <br />}<br />}<br />if(count%2 == 0)<br />dw[(int)pow(2,i)]='0';<br />else<br />dw[(int)pow(2,i)]='1';<br />}<br />printf(\"
\n CODE WORD is \n\n\"
);<br />for(i=1;i<12;i++)<br />printf(\"
%c\"
,dw[i]);<br />printf(\"
\n\nenter the received hamming code\n\n\"
);<br />scanf(\"
%s\"
,cw);<br />for(i=12;i>0;i--)<br />cw[i]=cw[i-1];<br />for(i=0;i<4;i++)<br />{<br />count=0;<br /> for(j=(int)pow(2,i);j<12;j+=(int)pow(2,i))<br /> <br /> {<br /> <br /> for(k=0;k<(int)pow(2,i);k++)<br /> <br /> {<br /> <br />if(cw[j]=='1')<br /> <br /> count++;<br /> <br /> j++;<br /> <br /> }<br />}<br /> <br /> if(count%2 != 0)<br /> <br /> error_pos=error_pos+(int)pow(2,i);<br />}<br />if(error_pos ==0)<br />printf(\"
\n\n There is no ERROR in received Code Word\n\"
);<br />else<br />{ <br />if(cw[error_pos]==dw[error_pos])<br />{<br /> <br /> printf(\"
\n\nThere are TWO or MORE Errors in received Code Word\n\n\"
);<br /> <br /> printf(\"
SORRY........! Hamming code cannot correct TWO or MORE Errors\n\"
);<br /> <br /> flag=1;<br />} <br />else<br />printf(\"
\nThere is an Error in bit position %d of received Code Word \n\n\"
,error_pos);<br />if(flag==0)<br />{<br />if(cw[error_pos]=='1')<br />cw[error_pos]='0';<br />else<br />cw[error_pos]='1';<br />printf(\"
\n\nCORRECTED CODE WORD is \n\n\"
);<br />for(i=1;i<12;i++)<br />printf(\"
%c\"
,cw[i]);<br />}<br />}<br />printf(\"
\n\n\"
);<br />}<br />7. Leaky bucket<br />#include<stdio.h><br />#include<math.h><br />#include<stdlib.h><br />int t_rand(int a)<br />{<br />int rn;<br />rn=random()%10;<br />rn=rn%a;<br />if(rn==0)<br />rn=1;<br />return(rn);<br />}<br />int main()<br />{<br />int packets[5],i,j,clk,b_size,o_rate,p_sz_rm=0,p_sz,p_time;<br />int flag=0;<br />system(\"
clear\"
);<br />for(i=0;i<5;++i)<br />packets[i]=t_rand(6)*10;<br />printf(\"
\n enter the output rate\n\"
);<br />scanf(\"
%d\"
,&o_rate);<br />printf(\"
\n enter the bucket size\n\"
);<br />scanf(\"
%d\"
,&b_size);<br />for(i=0;i<5;++i)<br />{<br />if((packets[i]+p_sz_rm)>b_size)<br />{<br />if(packets[i]>b_size)<br />printf(\"
\n incoming packet size (%d) is greater than bucket capacity %d\n p/c rejected\"
,packets[i],b_size);<br />else<br />printf(\"
\n bucket capacity exceeded\"
);<br />}<br />else<br />{<br /> <br /> for(j=0;;++j)<br />{<br />p_sz=packets[i];<br />p_sz_rm+=p_sz;<br />printf(\"
\nnew incoming packet size %d\"
,p_sz);<br />printf(\"
\nbyte-transmissions left:%d\"
,p_sz_rm);<br />p_time=t_rand(5)*10;<br />printf(\"
\n next packet will come at %d\"
,p_time);<br />for(clk=0;clk<=p_time;clk+=1)<br />{<br />printf(\"
\n time left:%d\"
,p_time-clk);<br />sleep(1);<br />if(p_sz_rm>=o_rate)<br />{<br />printf(\"
\n%d bytes transmitted\"
,o_rate);<br />p_sz_rm-=o_rate;<br />printf(\"
\n bytes remaining:%d\"
,p_sz_rm);<br />}<br />else<br />printf(\"
\nno packets to transmit!!\"
);<br />}<br />if(p_sz_rm!=0)<br />flag=1;<br />break;<br />}<br />}<br />}<br />return(0);<br />}<br />8. RSA<br />#include<stdio.h><br />#include<string.h><br />#include<math.h><br />int mul(unsigned int x,unsigned int y,unsigned int n)<br />{<br />unsigned long int k=1;<br />int j;<br />for(j=1;j<=y;j++)<br />k=(k*x)%n;<br />return(unsigned int)k;<br />}<br />int main()<br />{<br />int i;<br />char msg[100];<br />unsigned int pt[100],ct[100],n,d,e;<br />printf(\"
enter msg \n\"
);<br />scanf(\"
%[^\n]\"
,&msg);<br />for(i=0;i<strlen(msg);i++)<br />{<br />pt[i]=msg[i];<br />}<br />n=253;<br />d=17;<br />e=13;<br />for(i=0;i<strlen(msg);i++)<br />{<br />ct[i]=mul(pt[i],e,n);<br />}<br />printf(\"
\n Cipher Text=\"
);<br />for(i=0;i<strlen(msg);i++)<br />{<br />printf(\"
%d\"
,ct[i]);<br />}<br />for(i=0;i<strlen(msg);i++)<br />{<br />pt[i]=mul(ct[i],d,n);<br />}<br />printf(\"
\n Plain Text=\"
);<br />for(i=0;i<strlen(msg);i++)<br />{<br />printf(\"
%c\"
,pt[i]);<br />}<br />printf(\"
\n\"
);<br />}<br />9. TCP client<br />#include<stdio.h><br />#include<sys/types.h><br />#include<sys/socket.h><br />#include<netinet/in.h><br />#include<netdb.h><br />#include<string.h><br />int main(int argc,char *argv[])<br />{<br />int sockfd,newsockfd,portno,len,n;<br />char buffer[256],c[20000];<br />struct sockaddr_in serv,cli;<br />FILE *fd;<br />if(argc<2)<br />{<br />printf(\"
error :no port no\n usage:\n ./client portnumber\n ex:./client 7777\n\"
);<br />exit(1);<br />}<br />sockfd=socket(AF_INET , SOCK_STREAM,0);<br />bzero((char *)&serv,sizeof(serv));<br />portno=atoi(argv[1]);<br />serv.sin_family=AF_INET;<br />serv.sin_port=htons(portno);<br />if(connect(sockfd,(struct sockaddr *)&serv,sizeof(serv))<0)<br />{<br />printf(\"
server not responding.. \n\n\n\t i am to terminate.\n\"
);<br />exit(1);<br />}<br />printf(\"
enter the file with complete path\n\"
);<br />scanf(\"
%s\"
,&buffer);<br />if(write(sockfd,buffer,strlen(buffer))<0)<br />printf(\"
error writing to sock...\"
);<br />bzero(c,2000);<br />printf(\"
reading......\n...\n\"
);<br />if(read(sockfd,c,1999)<0)<br />printf(\"
error:read error..\n\"
);<br />printf(\"
client :displaying content of %s\n....\n\"
,buffer);<br />fputs(c,stdout);<br />printf(\"
\n....\n\"
);<br />return 0;<br />}<br />10. TCP server<br />#include<stdio.h><br />#include<sys/types.h><br />#include<sys/socket.h><br />#include<netinet/in.h><br />#include<netdb.h><br />int main(int argc ,char *argv[])<br />{<br />int sockfd,newsockfd,portno,len,n;<br />char buffer[256],c[2000],cc[20000];<br />struct sockaddr_in serv,cli;<br />FILE *fd;<br />if(argc<2)<br />{<br />printf(\"
error: no port no\n usage:\n ./server port num \n\"
);<br />exit(1);<br />}<br />sockfd=socket(AF_INET,SOCK_STREAM,0);<br />portno=atoi(argv[1]);<br />serv.sin_family=AF_INET;<br />serv.sin_addr.s_addr=INADDR_ANY;<br />serv.sin_port=htons(portno);<br />bind(sockfd,(struct sockaddr *)&serv,sizeof(serv));<br />listen(sockfd,10);<br />len=sizeof(cli);<br />printf(\"
server:\n waiting for connection..\"
);<br />newsockfd=accept(sockfd,(struct sockaddr *)&cli,&len);<br />bzero(buffer,255);<br />n=read(newsockfd,buffer,255);<br />printf(\"
\n server recv:%s\n\"
,buffer);<br />if((fd=fopen(buffer,\"
r\"
))!=NULL)<br />{<br />printf(\"
server:%s found \n opening and reading...\n\"
,buffer);<br />printf(\"
reading....\n.....reading complete\"
);<br />fgets(cc,2000,fd);<br />while(!feof(fd))<br />{<br />fgets(c,2000,fd);<br />strcat(cc,c);<br />}<br />n=write(newsockfd,cc,strlen(cc));<br />if(n<0)<br />printf(\"
error writing to socket..\"
);<br />printf(\"
\n transfer complete.\n\"
);<br />}<br />else<br />{<br />printf(\"
\n server:file not found!\n\"
);<br />n=write(newsockfd,\"
file not found!\"
,15);<br />if(n<0)<br />printf(\"
error: writing to socket..\"
);<br />}<br />return 0;<br />}<br />