Introduction exercises on 31.8.2012

2012 - 2013

M.Sc Jussi Laakkonen (Room: 2517)

Exercises:

• 1st period (Weeks 35,37,39,41) - Fridays 1215 - 1400
• 2nd period (Weeks 43,44,46) - Fridays 1215 - 1400

Additionally: two days (4.12.2011 & 5.12.2011) are reserved for Home examination demonstration.

Reception hour: Wednesday 1500 - 1600 (Room: 2517)

• Six (6) programming assignments
• One home examination.
• INVIDUAL WORK ! NO COPYING !
• It is required to attend to minimum of 5 out of 6 exercises.
  • Introduction lectures do not count.
  • All 6 assignments must be returned.
• At every exercise:
  • Couple of persons will be selected to present and EXPLAIN their code
  • Discussion about solutions, possible enhancements, etc.

• C language, GCC compiler, Linux (can be run on 6218 computers)
  • Compiles without errors or warnings (it would be good to follow ANSI C99 but not required on this course, use -std=gnu99)
  • Program runs without errors
• Comment your code (add name, student number and email to every file)
• Document your work (README: how to run, what has been done, own ideas)
• Use a makefile (mandatory)
• Use good structure for your code (divide code to functions and files)

• Program accepts appropriate parameters and handles them correctly.
• Program understands required commands and discards unknown commands.
• Connections can be created and maintained properly.
• Program can keep track of its state (connected, disconnected, sending data, receiving data etc.).
• Program discards (or reports) if invalid data is received from network.
• Program fulfills given assignment requirements.

• See evaluation flowchart.
• Maximum number of points per assignment is 11
• Bonus points can be gained from:
  • Implementing OPTIONAL features in assignment description
  • Own ideas and/or implementations
  • Answering to given guestions, well written and well reasoned answers might be rewarded.

• Put your code into SVN repository at https://www2.it.lut.fi/svn/courses/CT30A5001/
• Your login name is mapped to folder with your student number (read/write)
• Code will be checked out at deadline
  • only then, not before, not after
• Put into following directories:
  • A<n>, where <n> is the assignment number
  • E.g. Assignment 1 into A1, assignment 2 into A2, etc.
  • Except Home Examination, it goes into HE directory

• The directory should contain:
  • Code (documented in english or in finnish)
  • Headers
  • Readme (in english or in finnish)
  • Makefile
  • NO BINARY FILES

Before starting any assignment, read the instruction section from course main pages:

http://www2.it.lut.fi/wiki/doku.php/courses/ct30a5000/start#instructions

See also additional documents, tutorials etc. from wiki pages:

http://www2.it.lut.fi/wiki/doku.php/courses/ct30a5000/start#documents_standards_tutorials

• There are plenty of options, choose the one you like/know
• Vim/Emacs/gedit/nano/…
  • Note: Emacs might seem hard in the beginning..
  • Note: nano might not show all characters → annoying “bug hunt”
• See text_editors for information and tutorials
• Use e.g. helloworld.tar.gz for testing

• Terminal editor, starts in normal mode (editing not enabled)
• There is also Vim with GUI: gvim
• Usage: vim sourcecode.c or vi sourcecode.c
• Some basic commands:

  a      - append (start editing)
  i      - insert (start editing)
  esc    - quit editing
  :w     - save file
  :help  - help
  :q     - close help 
  :wq    - save and quit

• Esc -key quits current activity

• Graphical editor, start with gedit
  • E.g. gedit source1.c source2.c header.h
  • E.g with wildcards gedit *.c (all files ending with .c)
• Display line numbers, matching brackets, etc.
  • Edit → Preferences → View
• Enable automatic intendation:
  • Edit → Preferences → Editor
• Enable external commands such as make:
  • Edit → Preferences → External tools
  • Configure plugin for your purposes..
• Creates ~ -temp files, delete them before sending the assignment.

• When using computers remotely use terminal editor (Vim/Emacs/nano)
• Learn about screen -command (man screen)
  • Start command in new terminal screen:

    screen -S ScreenName ProgramToRun

    • E.g. start Vim in screen named EDITOR:

      screen -S EDITOR vim

  • Detach screen session: Ctrl-A Ctrl-D
  • Resume session, e.g. resume editor:

    screen -r EDITOR

• C-compiler (Gnu Project C and C++ Compiler)
• See man gcc or go to gcc.gnu.org
• Create a small test program and try to compile it.
• What flags we need for compiling c-code? How about debugging?
• Example (using helloworld.tar.gz):

  gcc helloworld.c -o helloworld

• “The purpose of the make utility is to determine automatically which pieces of a large program need to be recompiled, and issue the commands to recompile them.”
• See man make
• Makefiles:
  • Describes relationships among program.
  • Example:

    all:
       gcc helloworld.c -o helloworld

  • Remember: indentation with tab not spaces
  • Compile with:

    make

• The Gnu Debugger, can:
  • Start the program, give parameters

    gdb --args program arguments

  • Stop program on specified conditions
  • Examine what has happened
  • Change things in the program
• When something goes wrong, use this to see what went wrong (debug).
  • E.g. “mystic” segmentation faults etc.
• See man gdb for quick info (try ddd also, debugger with GUI)
• Use -g switch when compiling with gcc to enable debug symbols

• list = lists loaded code (list x = lists code around point x)
• break n/try = sets breakpoint to line n / breakpoint to function try
• step = runs next line of code
• next = same as previous but does not enter functions
• continue = continue execution, stops at next breakpoint
• where = shows current position
• quit = quits debugging
• Ctrl –c ends running program

• Add an infinite loop to your test program and debug it with GDB, e.g.

  while(1)
  {
    /*code*/
  }

• Stop the program in GDB with Ctrl-C (sends SIGINT)
• Run your program step by step with GDB
• Add variables to test program and learn about how to print the values of these variables in GDB

• A program for debugging and profiling
• Memory debugger
• See man valgrind
• Test if your program has memory leaks, e.g.

  valgrind ./helloworld

• Add a memory leak of one byte:

  #include <stdlib.h>
  /* some code */
  char *cpointer = (char *)malloc(sizeof(char));

• See what valgrind reports after this. How to remove this memory leak?

When using these computers you must follow the rules set by university and department administrators.

See departmental information for students:

http://www2.it.lut.fi/wiki/doku.php/admin/studentinfo

See information about class 6218:

http://www2.it.lut.fi/wiki/doku.php/admin/pentinkulma

APPARENTLY YOU NEED TO HAVE AN “OLD” ACCOUNT (NO NUMBERS) TO ACCESS SSH.LUT.FI AS IT IS NOT MAINTAINED ANYMORE…

Connecting with ssh outside university:

1. Connect with ssh to ssh.lut.fi with your university account (connections from Lnet are allowed).
   • E.g. ssh lutlogin@ssh.lut.fi
2. After login connect with ssh to selected class 6218 computer

If you have X-server running on your computer you can use graphical applications via ssh:

• Use X11 forwarding (in order to use graphical applications remotely), use e.g. ssh -X 0123456@ssh.lut.fi
  • Note: DO NOT RUN ANY OTHER PROGRAMS THAN SSH, SCP OR RLOGIN ON ssh.lut.fi machine
• Enable X11 forwarding for every connection.
• Note: if using cygwin, use -Y instead of -X

• Beej's Guide to Network Programming (read the usage of getaddrinfo() carefully, for getting local IP addresses see also getifaddrs())
• IPv6 Network Programming, Jun-Ichiro Itojun Hagino
  • Chapters: 1.4, 2.1, 2.2, 2.3, 4.1, 4.2, 4.3, 4.4, 4.5, 4.7
• TCP/IP illustrated, W. Richard Stevens
• TCP/IP Sockets in C: Practical Guide for Programmers, Michael J. Donahoo, Kenneth L. Calvert
• UNIX Network Programming: The Sockets Networking API Volume 1, W. Richard Stevens,Bill Fenner,Andrew M. Rudoff
• But be aware and beware: “GNU is not UNIX and Linux is not UNIX” && “Unix is a Linux-like operating system”, Jon “Maddog” Hall

Simple Hello World example including makefile.

NEW: udpexample2012.tar.gz

OLD: helloworld.tar.gz

• Extract:

  tar xzf helloworld.tar.gz

  • creates a directory “helloworld”
• See README-file in helloworld -directory

Simple UDP client and server example.

• Server listens a character from some client and quits.
• Client sends a character to given address and quits.

Unpack: udpexample2012.tar.gz

• creates a folder “udpexample”
• build with make

Simple TCP client and server example.

• Server listens for incoming connections and disconnects them right after accept().
• Server prints address information of the connected client.
• Client just connects and quits right after disconnection.

Unpack: tcpexample2012.tar.gz

• Creates a folder “tcpexample”
• build with make