RealmFiles/Notes/engine_protocol.md

The Realm Online: Engine & Protocol Documentation

1. Game Engine: Sierra Creative Interpreter (SCI) 2.1

The Realm Online was developed using a heavily modified version of the SCI 2.1 engine.

Key Modifications:

• Networking Stack: Unlike standard single-player SCI games (e.g., King's Quest), Realm includes a proprietary networking layer for real-time multiplayer interactions.
• Resource Management: Uses .res and .pqc (Packaged Quest Content) files for storing tiles, sprites, and sounds.
• Client Logic: Much of the client logic is written in SCI script (a Smalltalk-like language), but the core engine handles the rendering and networking primitives.

Tools for Asset Extraction:

• SCI Companion: A modern tool for editing and viewing SCI resources.
• QuickBMS: Can be used with custom scripts to extract files from .pqc archives.
• SCI Resource Viewer: Useful for browsing sprites and tiles.

2. Network Protocol

The game uses a client-server architecture with multiple dedicated TCP ports for different services.

Port Mapping:

• 6002 (Realm Server): Main game world communication.
• 6003 (Auth Server): Login and authentication.
• 6005 (Patch Server): Version checking and file updates.
• 7002 (Route Server): Redirects clients to specific game instances/realms.
• 8001 (Game Server): Individual game instance handling.

Handshake & Packet Structure:

Based on community reverse-engineering (e.g., the server_poc.py script):

• Framework: Many modern emulators use the Twisted framework (Python) to handle the asynchronous networking required.
• Packet Headers: Packets typically have a size header followed by the payload.
• Authentication: Involves a multi-step handshake where the client identifies itself, sends credentials, and receives a session token or redirection to a game server.

3. Database Schema

The community-maintained database (TRO-DB) provides schemas for the following:

• Mobs/NPCs: Statistics, drops, and spawn logic.
• Items: Equipment stats, consumable effects, and shop prices.
• Spells: Damage formulas, mana costs, and requirements.
• Maps: Area definitions, warp points, and shop inventory mappings.