Computer Networks Laboratory Fall 2011

Laboratory 1

Laboratory 1 Notes »

Subjects

Evaluation, Introduction
Bash commands
Working with files in C

Laboratory Assignments

Get from /etc/passwd all usernames that end in 'x' or 'z'. Redirect the output to output.txt file.
(BONUS) Using output.txt we want to write at the beging of the file the following "Am gasit utilizatorii:". In output.txt we have usernames that respect the following format 'firstname.lastname'. We want to change the 'lastname' of the user on the 4^th row with the following: "mylastname".

References

List of Linux Commands
An Introduction to GCC Book Online Version
GCC online documentation
Working with files Stream properties, indicators, functions, macros

Lecture Notes - Course 1 »

Contact

E-mail: stefan.negru at infoiasi.ro

Please use the following Subject field format of your emails concerning this laboratory: [CN] Message Title

Evaluation

The final grade is calculated using the following formula:
N = 0.3 * P + 0.4 * T + 0.2 * L + 1.

Where:

P – Mandatory Project to be delivered during weeks 13, 14, 15 or 16 (30% of the final grade); - more details »
T – Mandatory Test taken during week 16 (graded 1 to 10). The test will include course and laboratory subjects (40% of the final grade);
L – student's involvement during the laboratory, plus contribution and/or participation to the CN-related events – e.g., workshops, conferences, contests, other major public projects (20% of the final grade).

Important

In order to pass, each student must obtain minimum 5 points for P and T components.

More Details »

Laboratory 2

Laboratory 2 Notes »

Subjects

Process Management
Inter-process Communication
Signals

Laboratory Assignments

Compile,execute and explain the examples on the Course 2 Webpage
Create a program that will run in the background, and from 3 in 3 seconds will write a random number in a file. Details of implementation: the parent process will wait SIGUSR1 signal appearance, then it will create a child process, this will be the one that it will write in the file, the parent will wait for child process execution, at which point a message will be displayed.

References

Interprocess Communication Mechanisms
About Interprocess Communication
Interprocess Communication and Signals
List of available signals
All about Linux signals
Linux Signals for the Application Programmer
The Linux Programming Interface Book

Lecture Notes - Course 2 »

Laboratory 3

Mandatory Assignment - due until Laboratory 4 Laboratory 3 Notes »

Subjects

Inter-process Communication
Descriptors duplication
Pipes, FIFOs

Laboratory Assignments

Compile,execute and explain the examples on the Course 3 Webpage
Write a program that uses a single pipe for communication and in which:
- parent process writes a number in the pipe (read from the keyboard)
- child process checks if the number is prime and transmits the parent process the response (yes/no)
- parent process will display the response
Write a program to simulate the command: cat / etc / passwd | grep "account name"> account.txt, using FIFO's and duplications. Account name will read from the keyboard.
(BONUS) Implement a program to determine the maximum capacity of a pipe.

References

Duplicating Descriptors
Inter-process Communication part I Pipes, FIFOs
Introduction to Named Pipes
Working with Pipes in C
Using Pipes in Linux Processes

Lecture Notes - Course 3 »

Laboratory 4

Laboratory 4 Notes »

Laboratory Assignments

Compile,execute and understand the example soketpair.c on the Course 4 Webpage
Create a program in which a father process divides an arithmetic expression in a number of subexpressions. These subexpressions are each evaluated by a child process. The result is returned to the parent process, which will review the expression and return the final result. Communication will be implemented using socketpair().

Mandatory Assignment Evaluation

Implement the following inter-process communication protocol:

the communication is done in the parent process and executed by the child process;
the commands are givin as strings delimited by "new line";
the answers are byte strings prefixed by the response length;
the protocol includes the commands:
- login: username (validating the username by using the /etc/passwd file)
- cd path
- ls
- quit
the inter-process communication will be implemented using one of the known communication mechanism.

Important

Assignment is due Laboratory 4.

Lecture Notes - Course 4 »

Laboratory 5

Project Technical Report - due until Laboratory 7 Laboratory 5 Notes »

Subjects

Sockets
TCP client/server

Laboratory Assignments

Compile,execute and understand the example on the Course 5 Webpage
(BONUS) Modify the example above such that the clients will be processed concurrently using fork(). Watch out for zombie processes.
Develop a TCP server which upon receiving a number from a client, will return the incremented number to the client along with the client number.
Considering a configuration file using the following: (key:command):(e.g. 1111: /bin/ls: 2222: /bin/pwd: 3333:/bin.ps:). Develop a TCP server which will execute the command associate with a known key recieved from a client, anything else will return "Unknown key".

References

Sockets Tutorial
Client Server Model Architecture
About socketpair
Sockets Server and Client.
Learning UNIX. Part 3: System Calls, Sockets and IPC/2

Technical Report

Each chosen project must have a technical report associated with it. Until Laboratory 7 you must complete the following:

description of used technologies (learned so far at the Course) - depending on the project's implementation details; - This section will be completed as new technologies are being taught at the Course.
architectural and flow overview together with a survey of the concepts involved (provide details of how certain parts of your project work, interconnect each other and an analytical overview of the project; provide graphical diagrams);
partial implementation details (examples of portions source code used);
More details about Project Evaluation and Requirements.

Lecture Notes - Course 5 »

Laboratory 6

Laboratory 6 Notes »

Subjects

Concurrent TCP client/server

Laboratory Assignments

Considering a configuration file using the following: (key:command):(e.g. 1111: /bin/ls: 2222: /bin/pwd: 3333:/bin.ps:).
- Develop a concurrent TCP server which will execute the command associate with a known key recieved from a client, anything else will return "Unknown key".
- The client will display the result of the given command.
- The server will keep a history of the keys recieved from a client and will have a key associated with the history commad.
Adapt the mandatory assignment from Laboratory 4, so that the communication is done in a concurrent manner between a server and a number of clients.

References

Beej's Guide to Network Programming options for a socket;
Implementation of a Concurrent Server Using fork() (.doc file)
The GNU C Library Process Completion waitpid()
About waitpid() options
Using SO_REUSEADDR.

Lecture Notes - Course 6 »

Laboratory 7

Laboratory 7 Notes »

Laboratory Assignments

Compile,execute and understand the example on the Course 7 Webpage
Consider de exercises from Laboratory 5 and develop a UDP server/client instead of a TCP server/client.

Examples of technical reports/scientific articles(in .pdf format)

Example 1
Example 2
Example 3

Mandatory Assignment Evaluation - Technical Report

Each chosen project must have a technical report associated with it. Until Laboratory 7 you must complete the following:

description of used technologies (learned so far at the Course) - depending on the project's implementation details; - This section will be completed as new technologies are being taught at the Course.
architectural and flow overview together with a survey of the concepts involved (provide details of how certain parts of your project work, interconnect each other and an analytical overview of the project; provide graphical diagrams);
partial implementation details (examples of portions source code used);
More details about Project Evaluation and Requirements.

Technical Report recommended format - Springer LNCS

Important

Assignment is due Laboratory 7.

Lecture Notes - Course 7 »

Laboratory 8

Midterm - Project Work

Work on the project. Follow the guidelines:

the projects are individual;
the projects will be released under GNU GPL (General Public License);
the projects will be graded depending on the difficulty:
- (A) advanced - maxim 10 points;
- (B) medium - maxim 8 points;
- (C) easy - maxim 6 points;
- exceptional contributions will be graded additional 2 points;
mandatory project can be delivered during weeks 13, 14, 15;
during week 16 only A type projects, can be presented;
the project will have an attached documentation;
More details about Project Evaluation and Requirements.

Projects List »

Laboratory 9

Project Work.

Work on the project. Projects List »

Review Resurse Web in Romanian.

The Laboratory will be held during week 10 as 1^st December is Romania National Day.

Lecture Notes - Course 9 »

Laboratory 10

Laboratory 9 Notes »

Subjects

Synchronous Multiplexing I/O (Input/Output)
select()

Laboratory Assignments

Develop a program which will wait 6 seconds and 45 microseconds for the user to write something from the keyboard.
Develop a minichat which will use select() for handling sockets and descriptors.(hint: the server will use select to handle clients)
(2*BONUS) Solve the bug from the example provided in Course 9 Webpage. The bug appears when we connect the client to the server and no input is provided, and instead "CTRL + C" is pressed.

References

select() Documentation
select() Documentation 2
Programming GuideInput/Output Multiplexing
More Details aboutInput/Output Multiplexing

Lecture Notes - Course 10 »

Laboratory 11

Laboratory 10 Notes » and Laboratory 11 Notes »

Subjects

Out-Of-Band;
gethostbyname() | getaddrinfo(); gethostbyaddr() | getnameinfo().

Laboratory Assignments

Using the minichat developed during Laboratory 10, develop a mechanism for handling OOB data by considering the following:
- a client with administrator rights and can notify the server to send to another client (which does not have administrator rights) an OOB byte;
- when the client(the one that does not have administrator rights) recieves the OOB byte it will disconnet from the server.
Verify if the ports 8011 and 6089 are open on www.uaic.ro or www.emag.ro. Find the IP address of the websites using getaddrinfo().

References

Using Out-of-Band Data
Out-of-Band Data documentation 1
Out-of-band data documentation 2
Out-of-band data IBM documentation
gethostbyname and gethostbyaddr functions
getaddrinfo function
getnameinfo function

Lecture Notes - Course 11 »

Laboratory 12

Recuperare Laborator 12

Laboratoarele din saptamana 12 ( 22 Decembrie 2011 ) se vor recupera vineri 16 Decembrie 2011 dupa cum urmeaza:

Grupa B6 - C403 - orele 10⁰⁰ - 12⁰⁰;
Grupa B7 - C409 - orele 12⁰⁰ - 14⁰⁰;
Grupa A7 - C409 - orele 14⁰⁰ - 16⁰⁰.

Referatele vor fi predate pana pe 22 Decembrie 2011 (ora 23⁰⁰) prin e-mail la adresa: stefan.negru at infoiasi.ro in format electronic. In saptamana 13 (12 Ianuarie 2012) vor fi predate in format printat.

Laboratory 12 Notes »

Subjects

Threads

Laboratory Assignments

Considering a configuration file using the following: (key:command):(e.g. 1111: /bin/ls: 2222: /bin/pwd: 3333:/bin.ps:).
- Develop a concurrent TCP server that makes use of threads which will execute the command associate with a known key recieved from a client, anything else will return "Unknown key".
- The client will display the result of the given command.
- The server will keep a history of the keys recieved from a client and will have a key associated with the history commad.
(2*BONUS)Consider a producer/consumer scenario:
- The producer generates numbers from 1 to 10 in a random interval (between 0 and 100 milisec.) and stores them in a var.
- Each consumer will read the numbers from the producer and display them on the screen.