Experience Only Chat

Only Experience Chat

Stable - Can be used with minimal support by referencing documentation and examples


This plugin provides support for sending and receiving chat messages in a Morpheus project while offering flexible moderation options and custom data per message. Features include:

  • Broadcast chat messages to all MorpheusChatReceiverComponents via an authoritative MorpheusChatSenderComponent

  • Install arbitrary message filters into the chat server to accept or reject messages based upon custom rules

  • Have arbitrary actors act as moderators by giving them a MorpheusChatModeratorComponent

  • Assign custom data to each message which can be changed by moderators and filters

The plugin is based around a few main parts:

  • FMorpheusChatMessage

    This is the struct containing all relevant information about a chat message:

    struct FMorpheusChatMessage
        // Unique ID used to identify this message in the MorpheusChat plugin
        int32 MessageId;
        // The actor who sent this message via its MorpheusChatSenderComponent
        class AMorpheusActor* Sender;
        // The message content
        FString Message;
        // The server time when this message was initially received
        float ServerTime;
        // Project-specific data associated with this message
        int32 CustomData;
  • AMorpheusChatServer

    The chat server provides the backend for sending and receiving messages. It keeps track of all messages and broadcasts them via multicast to all clients. You should only have a single chat server in your world.

  • The three chat component types

    • AMorpheusChatSenderComponent

      Any actor with this component can attempt to broadcast a chat message to all receivers. Derived classes can override CanSendMessage to put restrictions on when to allow message broadcasting according to project rules.

    • AMorpheusChatReceiverComponent

      Each client actor with this component receives all chat messages multicast by the chat server. It's up to the project to decide what to do with each message, whether to cache a number of recent messages etc.

    • AMorpheusChatModeratorComponent

      An actor with a moderator component can act as a message filter and accept or reject messages based on project rules. They can also update custom data for already sent messages.

  • Message filters

    By default all messages received by the chat server are multicast to all receivers. However, projects can define custom rules to decide which messages are accepted and which should be rejected. This functionality is exposed via the IMorpheusChatFilter interface. Projects can implement arbitrary filters and install them into the chat server or into other filters that accept children.


To integrate the Chat plugin, follow these steps:

  1. Spawn an instance of AMorpheusChatServer into your server world

  2. Derive a class from AMorpheusChatReceiverComponent and override HandleMessageReceived. In your override, decide what to do with each message, e.g. expose it to UI, cache an array of the last messages etc. Put this component on each client-authoritative actor that needs to receive chat messages

  3. (optional) Override HandleUpdateCustomData on your receiver component if you want to support updating custom data for messages that were already sent. One use case would be where a moderator can decide later to highlight a message that was already sent by setting a flag in the custom data. Since you only receive the MessageId, you need to cache a reasonable number of received messages on the client and look it up yourself to get any benefit out of this feature

  4. Put a UMorpheusChatSenderComponent on all client-authoritative actors that should be able to broadcast messages

  5. (optional, recommended) Derive your own sender component and override CanSendMessage to control the conditions when a message is allowed to be sent. This function is called on both client and server.

  6. (optional, recommended) Write any number of message filters and install them into your chat server

  7. (optional) Derive a UMorpheusChatModeratorComponent and put it onto actors that should moderate messages before they are multicast to everyone. Register the component as a message filter in your chat server. Implement client-side UI to show pending messages to moderators so that they can accept or reject each message. Make sure you remove your moderator components from their parent filter before they are are destroyed so that their pending messages are correctly retried

  8. (optional) Associate custom data with your messages in your own filters or via the moderator component

Bandwidth considerations

This plugin multicasts messages to all client-side chat servers (and hence all receiver components) whenever the message passes all message filters. Due to the large scale nature of Morpheus projects, this could quickly lead to network congestion if you have no other means of throttling messages. It is therefore strongly recommended to implement a way to limit the amount of messages that can be sent per sender component in a given time frame. That limit depends on the number of senders you want to support inside the network stack you've set up for your project.

The plugin already offers a variety of filters that can be used for this purpose. See the list of common filters further below.

Filtering messages

A large part of the plugin revolves around the concept of filtering messages before they are broadcast to everyone. This is handled via the IMorpheusChatFilter interface:

// Interface to implement a chat filter. A chat filter can decide whether to accept or reject a message. Accepted messages are
// passed on to the next filter in the parent (if one exists). Rejected messages are discarded immediately. If the filter returns
// Pending, the filter now owns this message and must use the PendingMessageHandler to resolve it later
class IMorpheusChatFilter

    // Called initially if the parent filter supports pending messages. Should be stored by this implementation if it wants to
    // return Pending as a filter result. Upon returning Pending, it must use the stored Handler to accept or reject the message
    // at a later time
    virtual void SetPendingMessageHandler(TScriptInterface<IMorpheusChatPendingMessageHandler> Handler) = 0;

    // Process the message according to this filter's specification. DO NOT store the MessageCustomData reference. Changes to
    // MessageCustomData are applied independent of the filter result. For pending results, you can also change custom data when
    // accepting a message via the IMorpheusChatPendingMessageHandler interface later
    virtual EMorpheusChatFilterResult ProcessMessage(const FMorpheusChatMessage& Message, IN OUT int32& MessageCustomData) = 0;

    // Must be called by the parent filter after this filter was removed. If this filter contains any pending messages, it is
    // expected to call RetryMessage for all of them so that the messages aren't lost. In your implementation, also call this for
    // all owned child filters
    virtual void HandleFilterRemoved() = 0;

The main part of a filter is the ProcessMessage function which is called by the parent filter. In your implementation, decide what to do with the message that was passed in. There are three possible results:

enum class EMorpheusChatFilterResult
    // The message passed the filter successfully
    // The message was rejected and will be discarded
    // Message approval is pending. The filter will call back later

The chat server has a single filter slot which is initially empty. If no filter is installed, all messages are broadcast automatically. To install a filter, call InstallMessageFilter. In order to have more than one filter for your messages, you need to compose them from multiple filters. The plugin already comes with a number of default filters you can use:

  • UMorpheusChatRoundRobinFilter

    The round robin filter accepts an arbitrary number of child filters. Whenever it receives a message for processing, it forwards that message to the next child filter, wrapping around automatically. If no child filters are installed, messages are always accepted.

  • UMorpheusChatChainFilter

    The chain filter accepts an arbitrary number of child filters. Whenever it receives a message for processing, the message is passed through all of the filters until one of them returns Rejected or all of them eventually return Accepted. If a filter returns Pending, the chain is continued with the next filter in line once the pending message is resolved. If no child filters are installed, messages are always accepted.

  • UMorpheusChatAcceptIfModeratorFilter

    Automatically accepts all messages if the sender has a UMorpheusChatModeratorComponent. Otherwise processing is forwarded to the next filter. If no next filter is installed, messages are always accepted.

  • UMorpheusChatRateLimitFilter

    Accepts all messages but applies a rate limit to them. Messages are queued up and accepted according to the rate limit on each tick

  • UMorpheusChatOptionalFilter

    Helper class for an optional filter. If no child filter is registered, it accepts all messages, otherwise the child filter decides. This is useful for installing optional filters into a chain filter and keeping a reference to it without having to extract it from the chain filter.

  • UMorpheusChatQueueFilter

    Acts as a rate limiting filter by enforcing a maximum number of pending messages in flight in its child filter. This is useful as part of a load balancing strategy involving filters with user input.

  • UMorpheusChatLoadBalancingFilter

    This filter attempts to keep an equal load on child filters with pending messages. The child filter with the least number of pending messages always gets the next message. In case of ties, the filter picks the oldest filter that was registered.

  • UMorpheusChatPhraseFilter

    This filter searches for pre-configured phrases in a message and accepts or rejects the message depending on its mode and whether any of those phrases was found. This can be used as a profanity filter, for example.

There are also UMorpheusChatSingleChildFilterBase and UMorpheusChatChildFiltersBase for deriving your own filters that support child filters.

Pending messages

If a filter can't decide immediately whether to accept or reject a message, it can return EMorpheusChatFilterResult::Pending to indicate that the message will be resolved later. A common example would be the UMorpheusChatModeratorComponent. Chat moderation usually requires user input so the message has to be displayed to a moderator for consideration before it can be resolved.

To resolve a pending message, a second interface is used: IMorpheusChatPendingMessageHandler. If the parent filter supports pending messages, it should call SetPendingMessageHandler on its child filters and pass through a handler. Once a filter has decided what to do with a pending message, it can call AcceptPendingMessage or RejectPendingMessage on that interface. The chat server itself is a pending message handler and always calls SetPendingMessageHandler on its single filter.

If all filters eventually return Accepted, the message is broadcast to all receivers. If any filter returns Rejected, the message will be immediately discarded.

Retrying messages

If a filter has pending messages to resolve and it has to be removed from the game (e.g. a moderator actor leaving the game with unresolved messages), those messages need to be returned into the installed filter chain to ensure they are not lost. To facilitate this, filters can call RetryMessage on the IMorpheusChatPendingMessageHandler for all owned, pending messages. It depends on the message handler how retries are resolved. Generally, it should attempt to continue with the next filter in line.

Retrying messages should happen inside your override of HandleFilterRemoved. This function is called by the parent filter after your filter has been removed (and you need to ensure this happens when writing your own filters with child filters).

Composition example

Here's an example for how to compose filters:

void InstallFilters(AMorpheusChatServer* ChatServer, const TArray<UMorpheusChatModeratorComponent*>& Moderators)
    UMorpheusChatAcceptIfModeratorFilter* ModeratorPassthrough = NewObject<UMorpheusChatAcceptIfModeratorFilter>();

    UMorpheusChatRoundRobinFilter* RoundRobinFilter = NewObject<UMorpheusChatRoundRobinFilter>();

    for (const UMorpheusChatModeratorComponent* Moderator : Moderators)


This filter setup first checks if the message was sent by a moderator and auto-accepts it. If it wasn't sent by a moderator, it's passed on to the round robin filter which in turn contains all of the moderator components. So each moderator will get a message to resolve in a round robin fashion.

The moderator component always returns Pending, so only when the project-specific implementation has decided what to do with the message, it will pass and be fed back into the chat server.

Filter gotchas

  • It's your responsibility to ensure that filters are removed from their parent filter before they are destroyed (and hence retry their pending messages if necessary). The plugin assumes that all filters remain valid as long as they are installed.

  • Do not install the same filter instance twice. This could assign different PendingMessageHandlers depending on where they are added which would likely break the filter in either location

Custom data

FMorpheusChatMessage contains a CustomData property which is not used by the plugin or any of its common filters. Projects can use this field to associate arbitrary data with each message, e.g. to set flags whether to highlight a message, make it sticky etc. Custom data can be set in three ways:

  • UMorpheusChatSenderComponent

    When the sender component initially sends a message, it calls its protected GetInitialCustomData virtual function to determine the initial custom data to associate with that message. This only happens on the server.

  • Filters

    Each filter can change a message's custom data via the supplied MessageCustomData reference parameter. Changed custom data is always applied, regardless of which result the filter returns (although it won't have any effect if the filter returns Rejected since the message will be dropped!).

    IMorpheusChatPendingMessageHandler::AcceptPendingMessage also has a MessageCustomData parameter which is applied to the message. You need to ensure you cache the custom data value the message had when it entered your filter yourself if required.

    Common filters supplied by the plugin always pass through custom data unchanged.

  • Moderators

    Moderators can also change custom data for messages that were already broadcast in the past via UMorpheusChatModeratorComponent::ServerUpdateCustomData. This function calls HandleUpdateCustomData on all client receiver components. You have to ensure that you cache a reasonable number of sent messages to do anything with this call since you only receive the message ID, not the whole message.

Moderation with Community Sift

  1. Make sure the following is set up in the Live Config game.json. Get the exact URL paths from the Community Sift admin site, depending on exactly which ones your project is using. DefaultCategory is what will appear in the Server field in the chat logs and should be set to your project name.

    "Moderation": {
            "UseSimpleProfanityFilter": false,
            "UseWebChatFilter": true,
            "UseUrlFilter": true,
            "IgnoreCommunitySiftResponse": false,
            "UseSpeechToText": true,
            "CheckPlayerNames": true,
            "AllowBotsToSendChat": false,
            "CheckUsernameUrlPath": "/v1/workflow/call/fp_SOMEPROJECT_check_username",
            "CheckTextUrlPath": "/v1/workflow/call/fp_SOMEPROJECT_check_short_text",
            "CheckVoiceTranscriptUrlPath": "/v1/workflow/call/fp_SOMEPROJECT_check_short_or_long_text",
            "DefaultCategory": "SOME_PROJECT_ID"
  2. When setting up an allocation in GSS make sure the following fields are active

Reach out to Andrew Fenwick Alexander Landen or Content QA for URL and Password

Live Config settings

There are quite a few live config settings (see above) that affect moderation.

  • UseSimpleProfanityFilter This enables the old โ€œbanned word listโ€ filter, which rejects any message that contains any of the banned phrases. This is what was used for ScabLab but has been replaced by CommunitySift. The phrase list is also in live config, in profanity.json, but requires a server restart to take effect. The default is false.

  • UseWebChatFilter This causes chat (and voice transcriptions if enabled) to be sent to CommunitySift, so they show up in the chat logs and the senders can moderated.

  • UseUrlFilter This will block any text chat that looks like a URL from being broadcast, regardless of the response from CommunitySift.

  • UseAnsiFilter This will block any message that contains non-ANSI characters (that might be designed to circumvent other filters).

  • ClientUseUrlFilter and ClientUseAnsiFilter These are equivalent to the above, but run on the client. These filters can be expensive for the server to run, so if youโ€™re using trusted clients you can run them on the client and disabled them on the server.

  • IgnoreCommunitySiftResponse If enabled, all text chat will still be sent to CommunitySift, but the game wonโ€™t reject any messages based on the response. Enable this if you want to test data collection in CommunitySift but donโ€™t want to actually block any text chat.

  • UseSpeechToText This enables speech transcription, and sends the transcriptions to CommunitySift.

  • CheckPlayerNames This sends a playerโ€™s chosen name to CommunitySift for moderation before changing it.

  • AllowBotsToSendChat If disabled, bot chat wonโ€™t be sent to CommunitySift. This means itโ€™ll never get broadcast if UseWebChatFilter is enabled. Donโ€™t enable this with large numbers of bots unless youโ€™re performing a scheduled scale test and CommunitySift have been notified. Alternatively disable UseWebChatFilter to see the text in game as normal with no moderation.

  • CheckUsernameUrlPath / CheckTextUrlPath / CheckVoiceTranscriptUrlPath These specify the exact endpoints to send each of the requests to. Find them in the API docs page on the Community Sift website or talk to Andrew Fenwick or Thomas Wilkinson.

  • DefaultCategory This will appear in the Server field in the Community Sift chat logs, for differentiating between projects. Set it to your project name.

  • DefaultSubcategory This will appear in the Room field in the Community Sift chat logs. You could use this to differentiate between dev and production environments, or between different events etc.

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