Scribblers Backend Documentation

Overview

This document covers the backend server architecture and functionality.

Project Structure

Main Files

• server.js: Main entry point that initializes the Express server and Socket.io connections
• SocketServerHandler.js: Manages socket server interactions and client event listeners
• GameData.js: Handles game session data and round management

Classes

SocketHandler

Class: SocketHandler
Location: SocketServerHandler.js

This class manages socket initialization and event listeners for client-server communication.

Methods

createServerInstance(httpServer)

Creates and configures a new Socket.io server instance.

• Parameters:
  • httpServer - HTTP server created using an Express application
• Returns:
  • New Socket.io server instance on success
  • 0 on failure
• Configuration:
  • CORS: Allows connections from any origin
  • Methods: GET, POST

startServer(httpServer, port)

Starts the HTTP server on the specified port.

• Parameters:
  • httpServer - HTTP server created using an Express application
  • port - Port number to listen on

initializeServerListeners(server, client, gameDataMap)

Initializes Socket.io event listeners to handle client requests.

• Parameters:
  • server - Socket.io server instance
  • client - Socket.io client connecting to server
  • gameDataMap - Server-side map of game session data

Event Listeners

Event	Description
start-game	Starts a new game session in the specified room
play-again	Resets the game to play another round
create-new-lobby	Generates a unique room code and creates a new game session
join-room	Handles a player joining an existing room
leave-room	Manages player disconnection and room cleanup
reset-scores	Resets all player scores in a room
update-user-guess	Updates a player's guess and checks if all players guessed correctly
draw-init	Initializes drawing parameters for all clients
draw	Broadcasts draw coordinates to all clients
draw-end	Signals the end of a drawing action
draw-clear	Clears the canvas for all clients
draw-undo	Undoes the last drawing action
disconnect	Handles client disconnection

GameData

Class: GameData
Location: GameData.js

This class manages game session data and round mechanics.

Properties

Property	Type	Description
numberRounds	number	Total number of rounds configured for the game
currentRound	number	Current round number
maxPlayers	number	Maximum number of players allowed
players	array	Array of player avatars in the game
prompt	object	Current drawing prompt
drawer	string	Current player assigned to draw
timerID	number	Timer interval ID
timerValue	number	Current time remaining in seconds
playerData	Map	Player-specific data (scores, guesses)

Methods

constructor(numberRounds, currentRound, maxPlayers, players, prompt, drawer, timerID, timerValue, playerData)

Creates a new game session with specified parameters.

startNewRound(server, room, gameDataMap)

Begins a new round in the specified room.

• Parameters:
  • server - Socket.io server instance
  • room - Room identifier
  • gameDataMap - Server-side map of game session data
• Process:
  1. Clears previous guesses
  2. Increments round number
  3. Checks if game should end
  4. Selects a new drawer
  5. Generates new prompt
  6. Starts round timer

getPromptObject()

Randomly selects a drawing prompt, avoiding previously used prompts.

• Returns: A prompt object containing word and type

getPath(promptObject)

Forms the file path for the prompt image.

• Parameters:
  • promptObject - The selected prompt object
• Returns: Path to the prompt image

clearGuesses(server, room)

Clears all player guesses and updates clients.

• Parameters:
  • server - Socket.io server instance
  • room - Room identifier

allGuessesCorrect()

Checks if all players have guessed correctly.

• Returns: true if all non-drawing players guessed correctly, false otherwise

updateTimer(server, room, gameDataMap)

Updates the round timer and handles timer expiration.

• Parameters:
  • server - Socket.io server instance
  • room - Room identifier
  • gameDataMap - Server-side map of game session data

Game Constants

Prompts

The game includes drawing prompts organized by categories:

• Actions: Eat, Jump, Run, Sleep
• Animals: Bird, Cat, Dog, Elephant, Horse, Mouse
• Clothing: Glasses, Glove, Hat, Pants, Shirt, Shoe
• Food: Apple, Banana, Carrot, Grapes, Pizza, Spaghetti
• Shapes: Circle, Oval, Square, Triangle

Game Settings

• Round duration: 60 seconds
• Images per prompt: 3

Game Flow

1. Players create or join a room using a unique code
2. Host starts the game
3. For each round:
   • A random player is selected as the drawer
   • A random prompt is assigned
   • The drawer draws the prompt
   • Other players attempt to guess the word
   • Round ends when time expires or all players guess correctly
4. Game ends after the configured number of rounds

Server Initialization (server.js)

/**
 * This file it the main executable for the Scribblers backend. Node, Express, and Socket.io 
 * are used to listen for requests and send/receive game data.
 */
//  IMPORTING
const express = require('express'); // Creates backend server
const http = require('http'); // Creates HTTP server
const SocketServerHandler = require("./objects/SocketServerHandler.js"); // Manages socket server interactions

//  INITIALIZATIONS
const app = express(); // Express initialization
const server = http.createServer(app); // Create HTTP server using Express
const mappedGameData = new Map(); // Create global map to manage game data objects
const SocketServer = new SocketServerHandler(); // Create socket manager
const io = SocketServer.createServerInstance(server); // Create Socket.io server instance

// Event listener for new socket connections
io.on('connection', (socket) => {
    SocketServer.initializeServerListeners(io, socket, mappedGameData);
});

SocketServer.startServer(server, 3001);