Realtime messaging

Feature description

Realtime messaging is a sub-capability of Multiplayer lobby for sending custom data between players inside a room. Unity provides reliable channels and large-message fragmentation; Godot currently provides a JSON message entry point. Realtime messaging requires a room connection first and cannot be used before joining a room.

Supported engines

Engine	Status	Notes
Unity	Preview	Supports room messages, reliable transport, and large-message fragmentation.
GameMaker	Not supported	The first GameMaker release does not include realtime messaging.
Godot	In development	The preview runtime already supports sending and receiving JSON messages.

Prerequisites

• The minimal Rooms flow is complete.
• A room has been joined.
• Message types must not use SDK-reserved types.
• Message content should keep a stable structure so both ends can parse it.

By engine

Unity

using System;
using UnityEngine;
using IGP.UnitySDK;
using IGP.UnitySDK.Models;

public sealed class IGPChatDriver : MonoBehaviour
{
    [SerializeField] private IGPRuntimeManager runtimeManager;

    private void OnEnable()
    {
        runtimeManager.onMessageReceived.AddListener(OnMessageReceived);
    }

    private void OnDisable()
    {
        runtimeManager.onMessageReceived.RemoveListener(OnMessageReceived);
    }

    public async void SendChat()
    {
        await runtimeManager.SendMessageAsync(new Message
        {
            type = "chat.message",
            roomId = runtimeManager.CurrentRoomId,
            playerId = runtimeManager.PlayerId,
            reliable = true,
            content = new
            {
                text = "hello",
                sentAt = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(),
            },
        });
    }

    private void OnMessageReceived(string messageType, object content)
    {
        Debug.Log($"Message {messageType}: {content}");
    }
}

GameMaker

GameMaker currently does not support realtime messaging.

Godot

using Godot;
using IGP.GodotSDK.Autoload;

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

    public override void _Ready()
    {
        IGP.MessageReceived += OnMessageReceived;
    }

    public async void SendChat()
    {
        await IGP.SendMessageJsonAsync(
            "chat.message",
            "{\"text\":\"hello\"}",
            reliable: true);
    }

    private void OnMessageReceived(
        string messageType,
        string roomId,
        string playerId)
    {
        GD.Print($"Message {messageType} from {playerId}");
    }
}

Self-test

Engine	Checkpoint
Unity	Two clients are in the same room; after one sends a message, the other receives onMessageReceived.
GameMaker	Realtime messaging validation is not performed currently.
Godot	After sending a JSON message, the other endpoint receives the MessageReceived signal.

Troubleshooting

• Send succeeds but no message is received: confirm both clients are in the same room.
• Content parsing fails: validate with the simplest JSON string first.
• Unity large message send fails: prefer the reliable message entry point.
• Godot reports a reserved type error: use a business-defined message type name.