Messaging usage guide

The Messaging Service API is the Open Cloud equivalent of the Engine MessagingService, which lets you communicate across your game's servers and clients. The Engine API only allows you to write and update scripts manually in Studio for publishing messages, but the Open Cloud API lets you send messages to live servers from external tools to automate and improve your operations workflows.

Usage

There are several helpful tools that you can build by supporting cross-server communication with the Messaging Service API, including:

• Announcement Portals: A web portal can be helpful to support sending announcements to all users across servers in your game, such as announcing an upcoming event, an update, and the winner for a competition. On the portal, you can edit a message and click a button that calls the API to send the message out for all users or selected users.

• Moderation System: A moderation system can help keep your game safe and secure. When detecting a user with inappropriate behavior, you can publish a message to trigger the game server to warn or ban the specific user. You can also use data stores in the moderation system to add user accounts to a blocklist that prevents them from rejoining.

• LiveOps Dashboard: LiveOps dashboards are useful tools for managing live events, such as a Halloween party. On the dashboard, you can pre-code an event, update event messages, trigger the event when it's ready, and reward selected users with special items like a virtual crown without updating any of the game's code.

Limits

The Messaging Service API follows the same limits as the Engine MessagingService. Rate limits are shared across both APIs, and usage from both APIs is counted against the same limits.

Set up a topic for messaging

Before you can publish a message to your game's live servers, you must set up a topic, which is a customized message channel that is accessible from multiple servers. After defining a topic, you subscribe users to the topic in order to receive your incoming messages.

Currently, you can only define a topic in Studio and use the Luau API MessagingService:SubscribeAsync() to subscribe users to it. The following code sample subscribes any user to a topic when they join the game:

Set up and Subscribe Users to a Topic
local MessagingService = game:GetService("MessagingService")
local Players = game:GetService("Players")

local function onPlayerAdded(player)
	-- Define and subscribe to the topic
	local topic = "YourTopic"
	local connection = MessagingService:SubscribeAsync(topic, function(message)
		print(message.Data)
	end)

	player.AncestryChanged:Connect(function()
		-- Unsubscribe from the topic upon player ancestry change
		connection:Disconnect()
	end)
end

Players.PlayerAdded:Connect(onPlayerAdded)

Publish messages to live servers

After setting up a topic, publish a message to your game's live servers:

1. Create an API key on Creator Dashboard and copy it somewhere safe. Make sure you perform the following settings:

   1. Add messaging-service to Access Permissions.
   2. Select a game, and add the universe-messaging-service:publish operation.

2. Get the Universe ID for your game:

   1. Navigate to the Creator Dashboard.

   2. Find the game that you want to publish your messages to.

   3. Hover over a game's thumbnail, click the ⋯ button, and select Copy Universe ID.

      

3. Add the API key and universe to a POST request, as in this example:

   Example Request for Publishing a Message
   curl -L -X POST 'https://apis.roblox.com/cloud/v2/universes/{universe}:publishMessage' \
   -H 'x-api-key: {api-key}' \
   -H 'Content-Type: application/json' \
   --data '{
    "topic": "your-topic",
    "message": "Hello, everyone!"
   }'

4. Send the HTTP request to publish the message.

   If your request succeeds, it returns HTTP 200 with an empty response body.

Add the Messaging Service API to OAuth 2.0 apps

You can create OAuth 2.0 applications that allow your users to publish messages to their own live servers.

To use Messaging Service API for your application and request permissions from your users, perform the following settings:

1. When registering your application, under Permissions, select the universe-messaging-service:publish scope.

2. When implementing the authorization flow, include universe-messaging-service:publish in the scope parameter of the authorization URL that redirects users back to your application, like the following example:

   https://apis.roblox.com/oauth/v1/authorize?client_id=816547628409595165403873012&redirect_uri=https://my-app.com/redirect&scope=openid+universe-messaging-service:publish&response_type=Code&prompts=login+consent&nonce=12345&state=6789

3. Request access to the universeId of the game that the user wants to publish their messages to. Your application can send a POST request to the token resources endpoint with the access token, client ID and secret or the code challenge, depending on your implementation of your authorization flow, as request parameters to get a list of universeIds of games that the user granted permission to:

   Example Request
   curl --location --request POST 'https://apis.roblox.com/oauth/v1/token/resources' \
   --header 'Content-Type: application/x-www-form-urlencoded' \
   --data-urlencode 'token=<access_token>' \
   --data-urlencode 'client_id=<client_id>' \
   --data-urlencode 'client_secret=<client_secret>'

   This endpoint returns a list of universeIds like the following example response:

   Example Response
   {
     "resource_infos": [
       {
         "owner": {
           "id": "1516563360",
           "type": "User"
         },
         "resources": {
           "universe": {
             "ids": ["3828411582"]
           }
         }
       }
     ]
   }

4. Your application can now send messages to any game that a user has granted permission. When sending the request, include the access token in the authorization header and the universeId and topic in the request URI in the following format:

   Example Request
   curl --location --request POST 'https://apis.roblox.com/cloud/v2/universes/{universe}:publishMessage' \
   --header 'Authorization: Bearer <access_token>' \
   --header 'Content-Type: application/json' \
   --data-raw '{"topic": "some-topic","message":"message to publish"}'

Use with HTTPService

This API is one of the Open Cloud endpoints supported by HttpService. You can use it to publish messages across different games from within a game.