State and RPC

Feature description

State and RPC are sub-capabilities of Multiplayer lobby. State synchronizes shared room or player data, while RPC triggers named logic in the room. Both are used after the player joins a room.

Supported engines

Engine	Status	Notes
Unity	Preview	Supports state set / get / reset and RPC register / call / unregister.
GameMaker	Not supported	The first GameMaker release does not include state or RPC.
Godot	In development	The preview runtime already has JSON state and RPC calls.

Prerequisites

• The minimal Rooms flow is complete.
• A room has been joined.
• State keys and RPC names should remain stable.

By engine

Unity

using System;
using UnityEngine;
using IGP.Multiplayer;

public sealed class IGPStateRpcDriver : MonoBehaviour
{
    [SerializeField] private IGPMultiplayerRuntime runtimeManager;

    public async void SetGlobalScore()
    {
        await runtimeManager.SetGlobalStateAsync("match.score", new
        {
            red = 1,
            blue = 0,
            updatedAt = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(),
        });
    }

    public async void RegisterEchoRpc()
    {
        await runtimeManager.RegisterRPCAsync("sample.echo");
    }

    public async void CallEchoRpc()
    {
        var requestId = await runtimeManager.CallRPCAsync(
            "sample.echo",
            new { text = "hello" },
            "all");

        Debug.Log($"RPC request id={requestId}");
    }
}

Receive state and RPC messages through IGPMultiplayerRuntime.MessageReceived, then dispatch state_set, state_get, state_reset, rpc_call, or rpc_response message types. The SDK converts Content to StateSetContent, StateGetResponseContent, StateResetResponseContent, RPCCallContent, or RPCResponseContent. Use GetValue<T>() / GetData<T>() for game data instead of parsing JObject. Reply with RespondRPCAsync and pass RPCCallContent.CallerPlayerId as the target player.

GameMaker

GameMaker currently does not support state or RPC.

Godot

using Godot;
using IGP.GodotSDK.Autoload;

public partial class StateRpcPanel : Control
{
    private IGPGodotAutoload IGP =>
        GetNode<IGPGodotAutoload>("/root/IGP");

    public async void SetGlobalScore()
    {
        await IGP.SetStateJsonAsync(
            "global",
            "match.score",
            "{\"red\":1,\"blue\":0}");
    }

    public async void RegisterEchoRpc()
    {
        await IGP.RegisterRpcAsync("sample.echo");
    }

    public async void CallEchoRpc()
    {
        await IGP.CallRpcJsonAsync(
            "sample.echo",
            "{\"text\":\"hello\"}",
            "all");
    }
}

Self-test

Engine	Checkpoint
Unity	State changes are received after setting state; registered RPCs can be called and responses received.
GameMaker	State and RPC validation is not performed currently.
Godot	SetStateJsonAsync, GetStateAsync, and CallRpcJsonAsync can complete in sequence.

Troubleshooting

• State cannot be read: confirm scope and key match exactly.
• RPC is not triggered: first confirm the corresponding RPC name has been registered.
• Unity does not receive events: confirm IGPMultiplayerRuntime.MessageReceived is subscribed and inspect MessageType.
• Godot JSON fails: validate with a simple object string first, such as {"value":1}.