Chapter 8 — Networking

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Overview

RMAPI provides three networking systems built on top of Photon:

1. Mod Exchange — automatically shares your mod list with opponents (built-in, no code needed)
2. RaiseEvent System — send custom data to other players via RumbleMod
3. Custom Photon RPCs — register your own RPC methods for precise networked calls

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1. Mod Exchange (Automatic)

This works out of the box. When you join a match (Map0/Map1):

• RMAPI sends your mod list to the opponent via Photon event code 15
• When the opponent's list arrives, Actions.onModStringReceived fires
• You can then query the opponent's mods via Calls.Mods

You don't need to write any code for this. Just subscribe to the event if you want to react:

Actions.onModStringReceived += () =>
{
    if (Calls.Mods.doesOpponentHaveMod("MyCoolMod", "", matchVersion: false))
    {
        // Enable shared features
    }
};

See Chapter 3 — Game Queries for the full mod query API.

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2. RaiseEvent System (Custom Data)

For sending arbitrary data to other players, use the RumbleMod base class instead of MelonMod.

See Chapter 10 — RumbleMod Base Class for the full guide.

Quick summary:

using Il2CppPhoton.Realtime;
using Il2CppExitGames.Client.Photon;

public class MyMod : Utilities.RumbleMod  // inherit RumbleMod instead of MelonMod
{
    public override void OnLateInitializeMelon()
    {
        RegisterEvents();  // register with the event router
    }

    void SendSomething()
    {
        var data = new List<Il2CppSystem.Object>();
        data.Add((Il2CppSystem.String)"hello");

        RaiseEventOptions options = new RaiseEventOptions()
        {
            Receivers = ReceiverGroup.Others  // send to everyone except yourself
        };
        RaiseEvent(data, options, SendOptions.SendReliable);
    }

    public override void OnEvent(List<Il2CppSystem.Object> data)
    {
        // Received data from the other player
        string message = data[0].ToString();
    }
}

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3. Custom Photon RPCs

Photon RPCs let you call a specific method on a remote player's instance of a component. RMAPI patches Photon to support custom RPCs in modded components.

How It Works

1. You mark a method with [PhotonRPCs.PunRPC]
2. The method must be inside a class that inherits from MonoBehaviourPun (or a type registered with Il2Cpp)
3. RMAPI scans all loaded mods at startup and registers any methods with this attribute
4. Photon can then route RPC calls to your method

Defining an RPC

using RumbleModdingAPI.RMAPI;
using Il2CppPhoton.Pun;

public class MyNetworkComponent : MonoBehaviourPun
{
    [PhotonRPCs.PunRPC]
    public void SyncPosition(float x, float y, float z)
    {
        transform.position = new Vector3(x, y, z);
    }
}

Calling an RPC

Use Photon's standard photonView.RPC() to invoke it:

photonView.RPC("SyncPosition", RpcTarget.Others, 1.0f, 2.0f, 3.0f);

Registration Details

RMAPI handles registration automatically at startup:

• Scans every loaded MelonMod's assembly for methods with [PhotonRPCs.PunRPC]
• Adds each method name to PhotonNetwork.rpcShortcuts and PhotonNetwork.PhotonServerSettings.RpcList
• Patches SupportClass.GetMethods so Photon can discover your methods at runtime

You don't need to call any registration methods yourself.

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Which System Should I Use?

Scenario	Use
Check if opponent has a specific mod	Mod Exchange (automatic)
Send simple one-off data to opponent	RaiseEvent (via RumbleMod)
Sync state on a specific networked object	Custom Photon RPCs
Real-time continuous sync (positions, etc.)	Custom Photon RPCs

Key Differences

Feature	RaiseEvent	Photon RPCs
Requires specific component?	No (mod-level)	Yes (MonoBehaviourPun)
Routing	By mod name/author	By method name on a PhotonView
Data format	List<Il2CppSystem.Object>	Method parameters
Best for	Mod-to-mod messages	Component-level sync

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Tips

• Always check player count before sending network events — don't send if you're alone
• RaiseEvent uses Photon event code 18 — don't use that code for your own raw events
• Mod exchange uses code 15 — also reserved
• RPCs only work on objects with a PhotonView — that's a Photon requirement, not an RMAPI one
• Test with two instances — you need two players to test any networking

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