cn lab manual

AMRUTA INSTITUTE OF ENGINEERING AND MANAGEMENT SCIENCES

CN Lab Manual 7 sem laboratory work(10CSL77)

AIeMS 5/11/2013

This manual is for 7 Semester Computer Science and Information Science students (under VTU, Belgaum) to carry out their network lab programs. Network Simulator used is NCTUNS.

CN Lab Manual

Department of CSE/ISE, AIeMS,Bangalore

Networks Laboratory

Subject Code: 10CSL77 I.A. Marks : 25

Hours/Week : 03 Exam Hours: 03

Total Hours : 42 Exam Marks: 50

Note: Student is required to solve one problem from PART-A and one problem from

PART-B. The questions are allotted based on lots. Both questions carry equal marks.

PART A ( Simulation Programs)

1. Simulate a three nodes point – to – point network with duplex links between them. Set the

queue size and vary the bandwidth and find the number of packets dropped.

2. Simulate a four node point-to-point network with the links connected as follows:

n0 – n2, n1 – n2 and n2 – n3. Apply TCP agent between n0-n3 and UDP between n1-n3. Apply

relevant applications over TCP and UDP agents changing the parameter and determine the

number of packets sent by TCP / UDP.

3. Simulate the transmission of ping messages over a network topology consisting of 6 nodes and

find the number of packets dropped due to congestion.

4. Simulate an Ethernet LAN using n nodes (6-10), change error rate and data rate and compare

throughput.

5. Simulate an Ethernet LAN using n nodes and set multiple traffic nodes and plot congestion

window for different source / destination.

6. Simulate simple ESS and with transmitting nodes in wire-less LAN by simulation and

determine the performance with respect to transmission of packets.

PART B ( C/C++ Programs)

7. Write a program for error detecting code using CRC-CCITT (16- bits).

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

9. Using TCP/IP sockets, write a client – server program to make the client send the file name

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

10. Implement the above program using as message queues or FIFOs as IPC channels.

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

12. Write a program for congestion control using leaky bucket algorithm.

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Network simulators implemented in software are valuable tools for

researchers to develop, test, and diagnose network protocols. Simulation is

economical because it can carry out experiments without the actual hardware.

It is flexible because it can, for example, simulate a link with any

bandwidth and propagation delay or a router with any queue size and queue

management policy. Simulation results are easier to analyze than experimental

results because important information at critical points can be easily logged

to help researchers diagnose network protocols. Network simulators, however,

have their limitations. A complete network simulator needs to simulate

networking devices (e.g., hosts and routers) and application programs that

generate network traffic. It also needs to provide network utility programs

to configure, monitor, and gather statistics about a simulated network.

Therefore, developing a complete network simulator is a large effort. Due to

limited development resources, traditional network simulators usually have

the following drawbacks:

Simulation results are not as convincing as those produced by real

hardware and software equipment. In order to constrain their complexity and

development cost, most existing network simulators can only simulate real-

life network protocol implementations with limited detail, and this can lead

to incorrect results. For example, OPNET’s modeler product uses a simplified

finite state machine model to model complex TCP protocol processing. As

another example, in ns-2 package, it is documented that “there is no dynamic

receiver’s advertised window for TCP.”

The NCTUNS uses a distributed architecture to support remote

simulations and concurrent simulations. It also uses open-system architecture

to enable protocol modules to be easily added to the simulator. Functionally,

it can be divided into eight separate components described below:

• The first component is the fully-integrated GUI environment by which a user

can edit a network topology, configure the protocol modules used inside a

network node, specify mobile nodes' moving paths, plot performance curves,

play back animations of logged packet transfers, etc. From a network

topology, the GUI program can generate a simulation job description file

suite. Since the GUI program uses Internet TCP/IP sockets to communicate with

other components, it can submit a job to a remote simulation machine for

execution. When the simulation is finished, the simulation results and

generated log files are transferred back to the GUI program. The user then

can either examine logged data, plot performance curves, or play back packet

transfer animations etc. While a simulation is running at the remote

simulation machine, the user can query or set an object’s value at any time.

For example, the user may query or set the routing table of a router or the

switch table of a switch at any time. If the user does not want to do any

query or set operation during a simulation, the user can choose to disconnect

the currently running simulation so that he (she) can use the GUI program to

handle other simulation cases. The user can later reconnect to a disconnected

simulation at any time, whether it is still running or has finished. A user

thus can submit many simulation jobs in a short period of time. This can

increase simulation throughput if there are many simulation machines

available to service these jobs concurrently.

• The second component is the simulation engine. A simulation engine is a

user-level program. It functions like a small operating system. Through a

defined API, it provides useful and basic simulation services to protocol

modules.Such services include virtual clock maintenance, timer management,

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event scheduling, variable registrations, etc. The simulation engine needs to

be compiled with various protocol modules to form a single user-level

program, which we call the “simulation server.” When executed to service a

job, the simulation server takes a simulation job description file suite as

its input, runs the simulation, and generates data and packet transfer log

files as its output. When a simulation server is running, because it needs to

use a lot of kernel resources, no other simulation server can be running at

the same time.

• The third component is various protocol modules. A protocol module is like

a layer of a protocol stack. It performs a specific protocol or function. For

example, the ARP protocol or a FIFO queue is implemented as a protocol

module. A protocol module is composed of a set of functions. It needs to be

compiled with the simulation engine to form a simulation server. Inside the

simulation server, multiple protocol modules can be linked into a chain to

form a protocol stack.

• The fourth component is the simulation job dispatcher, which is a user-level program. It should be executed and remain alive all the time to manage

multiple simulation machines. We use it to support concurrent simulations on

multiple simulation machines. The job dispatcher can operate between a large

number of GUI users and a large number of simulation machines. When a user

submits a simulation job to the job dispatcher, the dispatcher will select an

available simulation machine to service this job. If there is no available

machine at this time, the submitted job can be queued in the dispatcher as a

background job. Background jobs are managed by the dispatcher. Various

scheduling policies can be used to schedule their service order.

• The fifth component is the coordinator, which is a user level program. On every machine where a simulation server program resides, a coordinator

program needs to be executed and remain alive. Its task is to let the job

dispatcher know whether this machine is currently busy running a simulation

or not. When executed, it immediately registers itself with the dispatcher to

join the dispatcher’s simulation machine farm. Later on, when its status

(idle or busy) changes, it will notify the dispatcher of its new status. This

enables the dispatcher to choose an available machine from its machine farm

to service a job. When the coordinator receives a job from the dispatcher, it

forks (executes) a simulation server to simulate the specified network and

protocols. At certain times during a simulation, the coordinator may also

fork (start) or kill (end) some real-life application programs, which are

specified in the job to generate traffic for the simulated network. Because

the coordinator has the process IDs of these forked traffic generators, the

coordinator passes these process IDs into the kernel to register these

traffic generators with the kernel. From now on, all time-related system

calls issued by these registered traffic generators will be performed based

on the virtual time of the simulated network, rather than the real time. When

the simulation server is running, the coordinator communicates with the job

dispatcher and the GUI program on behalf of the simulation server. For

example, periodically the simulation server sends the current virtual time of

the simulated network to the coordinator. The coordinator then forwards this

information to the GUI program. This enables the GUI user to know the

progress of the simulation. During a simulation, the user can also on-line

set or get an object’s value (e.g., to query or set a switch’s switch table).

Message exchanges happening between the simulation server and the GUI program

are all done by the coordinator.

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• The sixth component is the modifications that need to be made to the kernel

of the simulation machine so that a simulation server can correctly run on

it. For example, during a simulation, the timers of TCP connections used in

the simulated network need to be triggered by the virtual time rather than by

the real time.

• The seventh component is various protocol daemons (programs) running at the

user level. Like the routing daemon “routed” or “gated” running on UNIX

machines that exchange routing messages and set up system routing tables,

when the NCTUns is running to simulate a network, some protocol daemons can

run at the user level to perform specific jobs. For example, the real-life

“routed” (using the RIP routing protocol) or “gated” (using the OSPF routing

protocol) daemons can run with the NCTUns to set up the routing tables used

by the routers in a simulated network.

• The last component is all real-life application programs running at the

user level. As stated previously, any real life user-level application

program can run on a simulated network to generate network traffic, configure

network, or monitor network traffic, etc. For example, the tcpdump program

can run on a simulated network to capture packets flowing over a link and the

traceroute program can run on a simulated network to find out the routing

path traversed by a packet.

Note: Before executing any of the simulation program we should before the

following steps :

Step 1. open a terminal and execute the command dispatcher

Step 2. open one more terminal and execute the command coordinator

Step 3. open one more terminal and execute the command nctnusclient

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Program 1: Simulate a three nodes point-to-point network with

duplex links between them. Set the queue size vary the bandwidth

and find the number of packets dropped.

Note : Set the simulation time to 50 seconds(Menu->G-Settings->Simulation)

Step 1: Select the host icon on the toolbar and drag it onto the working

window. Repeat this for another host icon as shown in the above topology.

Step 2: Select the hub icon on the toolbar and drag it onto the working

window.

Step 3: Select the link icon on the toolbar and drag it on the screen from

host (node 1) to the hub and again from host(node 2) to the hub. Here the

hub acts as node 3 in the point-to-point network. This leads to the creation

of the 3-node point-to-point network topology. Save this topology as a .tpl

file by clicking of E(edit) button.

Step 4: Double-click on host (node 1), a host dialog box will open up. Then

click on Add, another dialog box pops up. Set start time to 0 and stop time

to 20 seconds. Click on the Command box and type the Command according to the

following syntax:

stg –u 1024 50 1.0.1.2

and click OK. Double click on node editor Select FIFO and set the queue size

to 50 and press OK. Select MAC, enable log statistics, select Throughput of

outgoing packets.

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following syntax:

rtg –u –w log1

and click OK. Double click on node editor Select FIFO and set the queue size

to 50 and press OK. Select MAC, enable log statistics, select Throughput of

incoming packets, select Number of Drop Packets and Number of Collisions

Step 6: Double click on the link between node 1 and the hub to set the

bandwidth to some initial value say, 10 Mbps. Repeat the same for the other

node.

Step 7: Click on the E(edit) button present on the toolbar in order to save

the changes made to the topology. Now click on the R button (Run simulation).

No simulation settings can be changed in this mode.

Step 8: Now go to Menu->Simulation->Run. Executing this command will submit

the current simulation job to one available simulation server managed by the

dispatcher. When the simulation server is executing, the user will see the

time knot at the bottom of the screen move. The time knot reflects the

current virtual time (progress) of the simulation case. After the simulation

is done we will find dark red line at the bottom of the screen.

Step 9: To start the playback, the user can click the start icon of the time

bar located at the bottom. The animation player will then start playing the

recorded packet animation.

Step 10: To view the results, go to the filename.results folder.

Step 11: Change the bandwidth on both the link say to 5 Mbps, and run the

simulation and compare the two results.

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Program 2: Simulate a four node point-to-point network, and

connect the links as follows: n0-n2, n1-n2 and n2-n3. Apply TCP

agent between n0-n3 and UDP n1-n3. Apply relevant applications

over TCP and UDP agents changing the parameter and determine the

number of packets by TCP/UDP.



window. Repeat this for another two host icon as shown in the above topology.


window.

Step 3: Select the link icon on the toolbar and drag it on the screen from

host (node 1- n0) to the hub and again from host(node 2- n1) to the hub and

also from host (node 3-n3) to the hub. Here the hub acts as n2. Save this

topology as a .tpl file by clicking of E(edit) button.




following syntax:

stcp –p 21 –l 1024 1.0.1.3

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and click OK. Double click on node editor Select MAC, enable log statistics,

select Throughput of outgoing packets.




following syntax:

stg –u 1024 20 1.0.1.3






following syntax:

rtcp –p 21 –l 1024

Click on Add once again, Set start time to 25 and stop time to 45 seconds.

Click on the Command box and type the Command according to the following

syntax:

rtg –u –w log1


select Throughput of incoming packets








is done we will find two dark red lines at the bottom of the screen.





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Program 3: Simulate the transmission of ping messaged over a

network topology consisting of 6 nodes and find the number of

packets dropped due to congestion.

Note: Set the simulation time to 500 seconds(Menu->G-Settings->Simulation)


window. Repeat this for another 5 host’s as shown in the above topology.


window. Connect the host’s to the hub as shown in the above topology.

Step 3: Save this topology as a .tpl file by clicking of E button.

Step 4. Double click on first host(node 1), a host dialog box will open up.

Then click on Add, another dialog box pops up. Set start time to 0 and stop

time to 50 seconds. Click on the Command box and type the Command according

to the following syntax:

stg –u 1024 50 1.0.1.4



Step 5. Double click on second host(node 2), a host dialog box will open up.




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stg –u 1024 50 1.0.1.4



Step 6. Double click on third host(node 3), a host dialog box will open up.




stg –u 1024 50 1.0.1.4



Step 7: Double-click on fourth host (node 4), a host dialog box will open up.


time to 50 seconds.Click on the Command box and type the Command according to

the following syntax:

rtg –u –w log1


select Throughput of incoming packets, select Number of Drop Packets and

Number of Collisions









Step 10: While the experiment is running, open an terminal on the system and

type the command on the command prompt as

ping 1.0.1.4

on executing this command we can see some icmp packets being sent to the

destination machine, which means that the destination machine is reachable.

If the command is changed to

ping 1.0.2.2

we can observe that an error message Network unreachable, which means that

the destination machine is not reachable as none of the system in the above

topology has an ip address 1.0.2.2

Note : With the above ping message can be tested. Next is to find the number

of packets drop

Step 10: To view the results (no of packets dropped), go to the

filename.results folder.

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Program 4: Simulate an Ethernet LAN using N-nodes(6-10), change

error rate and data rate and compare the throughput.


Step 1: Select the switch icon on the toolbar and drag it onto the working

window.


window. Repeat the same for another hub


window. Repeat this for another five host icon as shown in the above

topology.



Then click on Add, another dialog box pops up. Click on the Command box and

type the Command according to the following syntax:

stg –u 1024 50 1.0.1.4



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rtg –u –w log1
















Step 11: Now change the error rate to 0.2( error rate can be changed in node

editor of the receiving host(1.0.1.4) in the physical layer) but don’t change

the data rate (bandwidth) and note down the results. Similarly note down the

result by changing the error rate to 0.2 and data rate to 5 Mbps

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Program 5: Simulate an Ethernet LAN using n nodes and set

multiple traffic nodes and plot congestion window for different

source / destination.


Step 1: Select the switch icon on the toolbar and drag it onto the working

window.


window. Repeat the same for another hub


window. Repeat this for another five host icon as shown in the above

topology.





stg –u 1024 50 1.0.1.4



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rtg –u –w log1




Step 7. Double click on second host(node 2), a host dialog box will open up.



stg –u 1024 50 1.0.1.5



Step 8. Double click on third host(node 3), a host dialog box will open up.



stg –u 1024 50 1.0.1.5



Step 9: Double-click on fifth host (node 5), a host dialog box will open up.



rtg –u –w log1
















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Program 6: Simulate simple ESS and with transmitting nodes in

wire-less LAN by simulation and determine the performance with

respect to transmission of packets.


Step 1: Select/click the HOST icon on the toolbar and click the left mouse

button on the editor, to place HOST1 on the editor.

Step 2: Select/click the ROUTER icon on the toolbar and click the left mouse

button on the editor, to place ROUTER1 on the editor.

Step 3: Select/click the WIRELESS ACCESS POINT(802.11b) icon on the toolbar

and click the left mouse button on the editor, to place ACCESS POINT 1 on the

editor.Repeat this procedure and place ACCESS POINT 2 on the editor.

Step 4: Select/click the MOBILE NODE (infrastructure mode) icon on the

toolbar and click the left mouse button on the editor, to place MOBILE NODE 1

on the editor. Repeat this procedure and place MOBILE NODE 2, MOBILE NODE 3,

MOBILE NODE 4, MOBILE NODE 5,MOBILE NODE 6,MOBILE NODE 7 and MOBILE NODE 8 on

the editor.

Step 5: Click on the LINK icon on the toolbar and connect ACCESS POINT1 to

ROUTER1, ACCESS POINT2 to ROUTER1 and HOST to ROUTER1.

Step 6: Click on the “Create a moving path” icon on the toolbar and draw

moving path across MOBILE NODE 1,2, 3 and 4. Repeat for MOBILE NODE 5,6,7 and

8. (Accept the default speed value 10 and close the window, Click the right

mouse button to terminate the path).

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Step 7: Double click on ACCESS POINT1, click Wireless Interface and enable

transmission range. Repeat the same for ACCESS POINT2.

To create Subnet

Step 8: Have ctrl key pressed, select mobile node 1, 2, 3, 4 and access point

1 , go to N_Tools in tool bar , select 802.11(e) wireless network, select

generate 802.11(e) infrastructure mobile node , a window will pop up assign

subnet as 1 and gateway to 1.0.2.1( ip of router assigned to first subnet)

and repeat the same for the second subnet with the subnet value as 2 and

gateway value as 1.0.3.1( ip of the router assigned to second subnet).

Step 9: Click on the “E” icon on the toolbar to save the current topology.

Step 10: Double click the left mouse button while cursor is on HOST1 to open

the HOST window. Select Add button on the HOST window to invoke the command

window and provide the following command in the command textbox.

ttcp –r –u –s –p 8001

Click OK button on the command window to exit

Step 11: Repeat this step and add the following commands at HOST1

ttcp –r –u –s –p 8002

ttcp –r –u –s –p 8003

ttcp –r –u –s –p 8004

ttcp –r –u –s –p 8005

ttcp –r –u –s –p 8006

ttcp –r –u –s –p 8007

ttcp –r –u –s –p 8008

Step 12: Click NODE EDITOR Button on the HOST1 window and select the MAC

tab from the modal window that pops up. Select LOG STATISTICS and select

checkbox for Input throughput in the MAC window. Click OK button on the MAC

window to exit and once again click on the OK button on the HOST window to

exit.

Step 13: Double click the left mouse button while cursor is on MOBILE NODE 1

to open the MOBILE NODE window. Select Application tab and select Add button

to invoke the command window and provide the following command in the command

textbox.

ttcp –t –u –s –p 8001 1.0.1.1 (host’s ip address)

Step 14: Click NODE EDITOR Button on the MOBILE NODE1 window and select the

MAC tab from the nodal window that pops up. Select LOG STATISTICS and select

checkbox for Output throughput in the MAC window. Click OK button on the MAC

window to exit and once again click on the OK button on the MOBILE NODE1

window to exit.

Step 15: Repeat the above steps (step 13 and 14) for the MOBILE NODE 2, 3, 4

,5, 6, 7 and 8 and add the following commands at

MOBILE NODE 2:- ttcp –t –u –s –p 8002 1.0.1.1


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Step 16: Double click the left mouse button while cursor is on ROUTER1 to

open the ROUTER window. Click NODE EDITOR Button on the ROUTER1 window and

you can see three stacks. Two stacks for two ACCESS POINTS and another stack

for HOST1 which is connected to the ROUTER1.Select the MAC tab of ACCESS

POINT1 and Select LOG STATISTICS and select checkbox for Input throughput in

the MAC window. Click OK button on the MAC window to exit. Select the MAC tab

of ACCESS POINT2 and Select LOG STATISTICS and select checkbox for Input

throughput in the MAC window. Click OK button on the MAC window to exit.

Select the MAC tab of HOST1 and Select LOG STATISTICS and select checkbox for

Output throughput in the MAC window. Click OK button on the MAC window to

exit.

Step 17: Simulate

1. Click “R” icon on the tool bar

2. Select Simulation in the menu bar and click/ select RUN in the drop down

list to execute the simulation.

3. To start playback select play icon located at the bottom right corner of

the editor.

4. MOBILE NODE’s start moving across the paths already drawn.

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

bits).

Program-Name: crc.c

#include<stdio.h>

#include<unistd.h> #include<string.h>

int crc(char *input,char *output,char *gp,int flag)

{ int i,j;

strcpy(output,input); if(flag)

{ for(i=1; i<strlen(gp); i++)

strcat(output,"0");

} for(i=0; i<strlen(input); i++)

if(*(output+i) == '1') for(j=0; j<strlen(gp); j++)

{ if (((*(output+i+j) =='0') && (gp[j] == '0')) ||

((*(output+i+j) == '1') && (gp[j] == '1'))) *(output+i+j)='0';

else *(output+i+j)='1';

} for(i=0; i<strlen(output); i++)

if(output[i] == '1') return 1;

return 0;

}

int main() {

char input[50],output[50]; char recv[50], gp[50];

system("clear"); printf("\n Enter the input message in binary\n");

scanf("%s",input); printf("\n Enter the generator polynomial\n");

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scanf("%s",gp);

crc(input,output,gp,1); printf("\n The transmitted message is %s %s\n",input, output+strlen

(input)); printf("\n\n Enter the received message in binary \n");

scanf("%s",recv);

if(!crc(recv,output,gp,0))

printf("\n No error in data\n");

else

printf("\n Error in data transmission has occurred\n"); }

Compile and run

$ cc –o crc crc.c $ ./crc

$ Enter the input message in binary 1101011011

$ Enter the generator polynomial 10011

The transmitted message is 1101011011 1110

Enter the received message in binary 11010110111110

No error in data

Enter the received message in binary 11011110111110

Error in data transmission has occurred

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2. Write a program for distance vector algorithm to find suitable

path for transmission.

Program-Name: dv.c

#include<stdio.h>

#include<string.h>

struct node {

int dist[20]; int from[20];

}rt[10];

int main() {

int dmat[20][20]; int n,i,j,k;

system("clear"); printf("Enter The Number Of Nodes\n");

scanf("%d",&n);

printf("Enter The Cost Matrix\n"); for(i=1;i<=n;i++)

for(j=1;j<=n;j++) {

scanf("%d",&dmat[i][j]); dmat[i][i]=0;

rt[i].dist[j]=dmat[i][j]; rt[i].from[j]=j;

} for(i=1;i<=n;i++)

for(j=1;j<=n;j++) for(k=1;k<=n;k++)

if(rt[i].dist[j]>(rt[i].dist[k]+rt[k].dist[j])) {

rt[i].dist[j]=rt[i].dist[k]+rt[k].dist[j];

rt[i].from[j]=k; }

for(i=1;i<=n;i++) {

printf("State Value For Router %d is\n",i);

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for(j=1;j<=n;j++)

{ printf("\t\tVia %d Distance is %d",rt[i].from[j],rt[i].dist[j]);

} }

return 0; }

Compile and run

$ cc –o dv dv.c $ ./dv

Enter The Number Of Nodes

3 Enter The Cost Matrix

0 3 6 7 0 9

5 7 0 State Value For Router 1 is

Via 1 Distance is 0 Via 2 Distance is 3

Via 3 Distance is 6 State Value For Router 2 is

Via 1 Distance is 7


State Value For Router 3 is Via 1 Distance is 5


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3. Using TCP/IP sockets, write a client – server program to make

the client send the file name and to make the server send back

the contents of the requested file if present.

Program-Name: Client.c

#include<stdio.h> #include<sys/types.h>

#include<sys/socket.h> #include<netinet/in.h>

#include<arpa/inet.h> #include<fcntl.h>

#include<string.h> #include<stdlib.h>

#define SERV_HOST_ADDR "127.0.0.1"

int main(int agrc,char *argv[]) {

int sockfd; struct sockaddr_in servaddr,cliaddr;

char filename[10],buf[1000]; int n;

servaddr.sin_family=AF_INET;

servaddr.sin_addr.s_addr=inet_addr(SERV_HOST_ADDR); servaddr.sin_port=htons(atoi(argv[1]);

sockfd=socket(AF_INET,SOCK_STREAM,0);

if(sockfd<0) {

printf("Client:cant open stream socket\n");

exit(0); }

else printf("Client:stream socket opened successfully\n");

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

{

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printf("Client:cant connect to server\n");

exit(0); }

else printf("Client:connected to server successfully\n");

printf("\n Enter the file name to be displayed :");

scanf("%s",filename); write(sockfd,filename,strlen(filename));

printf("\n filename transferred to server\n"); n=read(sockfd,buf,1000);

buf[n]=’\0’;

printf("\n Client : Displaying file content of %s\n",filename); printf(“%s”,buf);

close(sockfd); exit(0);

}

Program-Name: Server.c

#include<stdio.h>

#include<sys/types.h> #include<sys/socket.h>

#include<netinet/in.h> #include<arpa/inet.h>

#include<fcntl.h> #include<string.h>

#include<stdlib.h>

#define SERV_HOST_ADDR "127.0.0.1"

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

{ int sockfd,newsockfd,clilen;

struct sockaddr_in cliaddr,servaddr; char filename[10],buf[1000];

int n,fd;

servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY);

servaddr.sin_port=htons(atoi(argv[1]);

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sockfd=socket(AF_INET,SOCK_STREAM,0);

if(sockfd<0) {

printf("Server:cant open stream socket\n"); exit(0);

} else

printf("Server:stream socket opened successfully\n");

if((bind(sockfd,(struct sockaddr *) &servaddr,sizeof(servaddr)))<0)

{

printf("Server:cant bind local address\n"); exit(0);

} else

printf("Server:bind to local address\n");

listen(sockfd,5); printf("\n SERVER : Waiting for client...\n");

clilen=sizeof(cliaddr); newsockfd=accept(sockfd,(struct sockaddr *)&cliaddr,&clilen);

if(newsockfd<0) {

printf("server:accept error\n"); exit(0);

}

else printf("Server: accepted\n");

n=read(newsockfd,filename,10);

filename[n]='\0'; printf("\n SERVER : %s is found and ready to transfer

\n",filename);

fd=open(filename,O_RDONLY);

if(fd==-1) {

write(newsockfd,”File doesn’t exists”,25); exit(0);

} n=read(fd,buf,1000);

buf[n]='\0';

write(newsockfd,buf,n);

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printf("\n transfer success\n");

close(newsockfd); exit(0);

}

Compile and run

- open first terminal, compile and run server there - open second terminal, compile and run client there

$ cc –o ser Server.c $ ./ser 8500

Server:stream socket opened successfully

Server:bind to local address SERVER : Waiting for client...

Server: accepted SERVER : aiems is found and ready to transfer

transfer success

$ cc –o cli Client.c $ ./cli 8500

Client:stream socket opened successfully Client:connected to server successfully

Enter the file name to be displayed : aiems

filename transferred to server Client : Displaying file content of aiems

Welcome to aiems computer science department.

This is CN lab

NOTE : If the program has to be executed on the network say on two different machines then

Change the ipddress in the header file(inet.h) from 127.0.0.1 to the

ipaddress of the machine(first machine), where the server program has to be typed , compiled and executed.

Type the client program on the other machine(second machine) , compile it and then execute

CN Lab Manual


4. Implement the above program using as message queues or

FIFOs as IPC channels.

Program-Name: fclient.c

#include<stdio.h>

#include<fcntl.h> #include<string.h>

#include<stdlib.h> #include<sys/types.h>

#include<sys/stat.h> #include<unistd.h>

int main()

{ char filename[10],buf[1000];

int n,fd1,fd2; mknod("fifo1",S_IFIFO | 0666,0);

mknod("fifo2",S_IFIFO | 0666,0);

printf(“\n Client Online \n”); fd1=open("fifo1",O_WRONLY);

if(fd1 == -1) {

printf(“\n error in opening fifo file”); exit(0);

} printf("\n Enter the filename...\n\n");

scanf("%s",filename); write(fd1,filename,strlen(filename));

printf("\n waiting for reply...\n"); fd2=open("fifo2",O_RDONLY);

if(fd2 == -1) {

printf(“\n error in opening fifo file”);

exit(0); }

n=read(fd2,buf,1000); buf[n]='\0';

printf("\n File received ..the contents are...\n"); puts(buf);

close(fd1); close(fd2);

unlink("fifo1"); unlink("fifo2");

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exit(0);

}

Program-Name: fserver.c

#include<stdio.h>

#include<fcntl.h> #include<stdlib.h>

#include<string.h> #include<sys/types.h>

#include<sys/stat.h> #include<unistd.h>

int main()

{ char filename[10],buf[1000];

int n,fd1,fd2,fd;

mknod("fifo1",S_IFIFO | 0666,0); mknod("fifo2",S_IFIFO | 0666,0);

printf("\n Server Online\n"); fd1=open("fifo1",O_RDONLY);

if(fd1 == -1) {

printf(“\n error in opening fifo file”); exit(0);

} n = read(fd1,filename,10);

filename[n]='\0'; fd2=open("fifo2",O_WRONLY);

if(fd2 == -1) {

printf(“\n error in opening fifo file”);

exit(0); }

fd=open(filename,O_RDONLY); if(fd==-1)

{ write(fd2,”File doesn’t exists”,25);

unlink("fifo1"); unlink("fifo2");

close(fd1); close(fd2);

close(fd);

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exit(0);

} n=read(fd,buf,1000);

buf[n]='\0'; write(fd2,buf,n);

printf("\n SERVER :Transfer completed\n"); unlink("fifo1");

unlink("fifo2"); close(fd1);

close(fd2); clode(fd);

exit(0);

}

Compile and run - open first terminal, compile and run server there

- open second terminal, compile and run client there

$ cc –o ser fserver.c $ ./ser

Server Online

Sever: aiems is found! transferring the contents

SERVER :Transfer completed

$ cc –o cli fclient.c

$ ./cli CLient Online!

CLIENT : enter the filename... aiems File received ..the contents are...

Welcome to aiems computer science department.

This is CN lab

CN Lab Manual


5. Write a program for simple RSA algorithm to encrypt and

decrypt the data.

Program-Name : rsa.c

#include<math.h>

#include<stdlib.h> #include<stdio.h>

long gcd(long a,long b)

{ long r;

while(b!=0) {

r=a%b; a=b;

b=r; }

return a;

}

int main() {

char message[100];

long p,q,n,phi,i,e=0,d=0; long nummes[100]={0};

long encrypted[100]={0},decrypted[100]={0};

printf("Enter The Message To Be Encrypted\n"); gets(message);

printf("\nenter value of p and q\n"); scanf("%ld%ld",&p,&q);

n=p*q;

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

for(i=2;i<phi;i++) if(gcd(i,phi)==1) break;

e=i;

for(i=2;i<phi;i++)

if(((e*i)%phi)==1)break; d=i;

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for(i=0;i<strlen(message);i++) nummes[i]=message[i];

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

{ encrypted[i]=1;

for(j=0;j<e;j++) encrypted[i] = (encrypted[i]*nummes[i])%n;

}

printf("\n Encrypted message\n");

for(i=0;i< strlen(message);i++) printf(" %ld ",encrypted[i]);

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

{ decrypted[i]=1;

for(j=0;j<d;j++) decrypted[i]=(decrypted[i]*encrypted[i])%n;

}

printf("\n Decrypted message\n "); for(i=0;i< strlen(message);i++)

printf("%c",(char)(decrypted[i])); return 0;

}

Compile and run $ cc –o rsa rsa.c

$ ./rsa

Enter The Message To Be Encrypted aiems bangalore

enter value of p and q 37 71

Encrypted message 1914 1981 2560 1670 –1602 1138 1981 76

Decrypted message aiems Bangalore

CN Lab Manual


6. Write a program for congestion control using leaky bucket

algorithm.

Program-Name :Congestion.c

#include<stdio.h>

#include<string.h>

int minimum(int x,int y)

{ if(x<y)

return x; else

return y; }

int main()

{ int nsec,bsize,oprate,i,drop=0,min,count=0,input[25];

system("clear"); printf("Enter The No. Of Seconds You Want To Stimulate\n");

scanf("%d",&nsec); printf("Enter The Bucket Size\n");

scanf("%d",&bsize);

printf("Enter The Processing Rate\n"); scanf("%d",&oprate);

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

{ printf("Enter The Size Of The Packet Entering At %d sec\n",i+1);

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

printf("\nSecond|Packet Recieved|Packet Sent|PacketLeft|Packet

Dropped|\n"); printf("--------------------------------------------------------------\n");

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

{

count=count + input[i]; if(count>bsize)

{

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drop=count-bsize;

count=bsize; }

printf("%d\t",i+1); printf("%d\t\t",inp[i]);

min=minimum(count,process); printf("%d\t\t",min);

count=count-min; printf("%d\t\t",count);

printf("%d\n",drop); drop=0;

}

for(;count!=0;i++)

{ printf("%d\t",i+1);

printf("0\t\t"); min=minimum(count,process);

printf("%d\t\t",min); count=count-mini;

printf("%d\t\t",count); printf("%d\n",drop);

}

}

Compile and run

$ cc –o Congestion Congestion.c

$ ./Congestion

Enter The Bucket Size 5

Enter The Processing Rate 2

Enter The No. Of Seconds You Want To Stimulate 3

Enter The Size Of The Packet Entering At 1 sec 5

Enter The Size Of The Packet Entering At 1 sec 4

Enter The Size Of The Packet Entering At 1 sec

3

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Second|Packet Recieved|Packet Sent|PacketLeft|Packet Dropped| ----------------------------------------------------------------------------

1 5 2 3 0 2 4 2 3 2

3 3 2 3 1 4 0 2 1 0

5 0 1 0 0