Unreal Text Chat
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In The M2 Example Plugin, we have a simple example chat system that can be used for small/medium sized experiences. It doesn't use an external web service (e.g. PubNub), instead handling the messaging through the Unreal machines, via Morpheus networking.
This is the morpheus actor that handles the networking involved in sending these Unreal text chat messages. Clients call SendChatMessage, which sends an RPC to the server. The server then reviews the message, and broadcasts it to the clients via a multicast RPC.
We add a ProcessMessage step at the point of receiving a Server_SendChatMessage RPC, which acts as an entry point for adding moderation/chat filtering. The example is just a simple check that rejects messages that are too long, but more complex moderation could be added here, such as rejecting certain words, or interacting with an external service like CommunitySift.
(Note that adding complex logic to this ProcessMessage method may slow the server down at scale, since the computation is being run on the server for each message that gets processed in this example)
To hit the aforementioned scaletest limits (can handle bots sending messages simultaneously up to 3k, but has noticeable server slowdown at 5k, with the client handling everything fine), we needed to add some rate limiting. This achieves two benefits: it reduces the amount of multicast messages broadcasted per tick, so reduces the network load of the system, but also, more importantly, it limits the number of messages received by the client per tick, reducing the amount of widgets it adds per tick.
The rate limiting we added in the example is a basic implementation: for every approved message, we add it to a queue, and then broadcast a limited number (defaulting to 3) every tick. If we receive too many messages in one tick, we drop the excess (defaulting to 200).
This component is added to the character's MorpheusActor, and is responsible for communicating with the singleton, sending messages through it, and listening to messages received by it.
This is the widget added to the example HUD that listens to the text chat component, adding any received messages to the "message history", and sending any messages typed in to the input box (WBP_M2Example_TextChatInputField).
WBP_M2Example_TextChatMessage and WBP_M2Example_TextChatInputField have some added logic to handle adding emojisto the messages.
Adding widgets is a nontrivial operation for the client, so adding a large number of messages in a single tick is going to slow down the client. In this example we have mitigated this with the rate limiting done by the singleton, limiting it so that just a few messages are received per tick.
Currently the component has backwards compatibility with the old PubNub Text Chat component, allowing the component to send messages through that system instead, if UsingPubnubChat is set to true. By default, the web component of this text chat is not active, but can be enabled, as outlined in:
