GoldbergLocalCoop

Goldberg Local Coop

Enables local co-op multiplayer for Risk of Rain 2 using the Goldberg Steam emulator.

What This Does

This mod patches RoR2's networking layer to properly handle P2P connections from Goldberg Steam emulator instances. Without this mod, joining players get disconnected when the host starts the game.

Use Cases

• Local co-op: Run multiple game instances on the same machine
• LAN parties: Play without Steam authentication requirements
• Offline play: No internet connection needed

Requirements

• BepInEx (mod loader)
• Goldberg Steam Emulator (Steam API emulation)

Installation

• Install BepInEx if you haven't already
• Download this mod
• Place RoR2LocalCoop.dll in BepInEx/plugins/

Setup Guide

For Each Game Instance

• Create a separate game folder with Goldberg's steam_api64.dll
• Configure unique Steam IDs in steam_settings/ for each instance
• Launch both instances

In-Game

• Both instances: Settings -> Disable crossplay
• Host: Multiplayer -> Host Game -> Create
• Host: Copy Lobby ID to clipboard (button in lobby)
• Client: Multiplayer -> Join Clipboard Lobby
• Host: Click Start Game
• Both players load in!

How It Works

When RoR2 receives P2P network data, it checks if the sender has a registered connection. Goldberg emulator connections weren't being registered properly, causing data to be rejected.

This mod:

• Force-accepts P2P connections from Goldberg Steam IDs
• Properly registers the connection object so data isn't rejected

Goldberg Steam IDs

The mod automatically allows Goldberg's default ID range:

• 76561198000000001 through 76561198000000010

Compatibility

• Works with most other mods
• Does not affect normal online multiplayer
• Only activates for Goldberg Steam ID ranges

Source Code

GitHub Repository

Credits

Built with BepInEx and Harmony.