lem-ipc (@42Paris)

This project was coded for Linux. Here is the subject.

About

lem-ipc is a little game to understand how mutliple processes can communicate between themselves using the UNIX System V IPC.

System V IPC is the name given to three interprocess communication mechanisms that are widely available on UNIX systems: message queues, semaphore, and shared memory.

The game consist of a grid filled with players from different teams (maximum 7 different teams), with each team fighting each other and trying to be the last team standing.

Building and running the project

1. Download/Clone this repo

    git clone https://github.com/llefranc/42_lem-ipc
   

2. cd into the root directory and run make or make debug for additional logs

    cd 42_lem-ipc
    make
   

3. Run several time lemipc in different terminals with a team number between 0 and 7

    # Two players in team 1 vs one player in team 2, and the graphic mode
    ./lemipc 1
    ./lemipc 1
    ./lemipc 2
    ./lemipc 0   # graphic mode
   

Modes

	./lemipc [team-number]

lemipc can be launch in two different modes : graphic mode or player mode.

The mode is determinated based on the team number provided as argument.

During the game, you will have:

• one lemipc instance for the graphic mode.
• and x lemipc instances for x players alive.

Graphic mode

	./lemipc 0

To launch the graphic mode, you need to run lemipc with 0 as team number.

The graphic mode display the grid with the position of each player, and refreshed the grid each time a player mooves.

• ⚠️ Only one instance of the graphic mode can run at any time ⚠️
• ⚠️ The graphic mode must run during the game, otherwise the game ends immediately ⚠️

graphic mode example

Player mode

	./lemipc [1-7]

To launch the player mode, you need to run lemipc with a team number between 1 and 7.

The player is automatically mooved on the grid when it's it turn based on a very simple IA.

player mode example

Lobby

When launching the first instance of lemipc, this one will init the shared ressources and init a starting time.

A timer will then be displayed, and other lemipc instances can joined the game during this time.

The game is launched when the timer reaches 0. At this point, no other instances will be able to join the game.

The waiting time is defined with the macroconstant SEC_START_TIME in game_utils.h. You can change this value to increase or decrease the lobby waiting time.

Game rules

The game is designed based on the following rules:

• ➡️ Each player is represented by its team number on the grid.
• ➡️ Each second a player mooves.
• ➡️ A player can move only on an empty tile.
• ➡️ A player can move only in 4 directions (up, down, left and right).
• ➡️ A player can move several times in a row.
• ➡️ You cannot differentiate players from the same team on the grid.
• ➡️ All the players of a same team target all together the same ennemy player.
• ➡️ When two players from the same team surround an ennemy player, this one dies (diagonals works).
• ➡️ It's mandatory for a player to move when it's its turn, even if it's just next to its target.
• ➡️ The game stop when only one team is remaining.

System V mechanics

The three interprocess communication mechanisms of System V are used the following way:

• shared memory segment: contain the map and game datas.
• semaphore sets : secure the access of the shared memory segment.
• message queue : allow the players of a same team to exchange the ennemy player ID to focus.

The first instance of lempic to be launch will init all the System V ressources; the last instance to exit will destroy all the System V ressources.