Events

All changes to the chat state are exposed as events. When a new message is sent, a reaction is added, or any other action occurs, the client receives an event in real-time. You can also send custom events, enabling you to build your own pub/sub functionality on top of a channel.

Listening for Events

The code sample below shows how to listen to events:

channel.on("message.new", (event) => {
  console.log("received a new message", event.message.text);
});

channel.on("message.deleted", (event) => {
  console.log("message was deleted", event.message.id);
});

val channelClient = client.channel("messaging", "general")

// Subscribe for new message events
val disposable: Disposable = channelClient.subscribeFor<NewMessageEvent> { newMessageEvent ->
  val message = newMessageEvent.message
}

// Dispose when you want to stop receiving events
disposable.dispose()

// There are 2 ways to listen for events
// 1. Use an EventsController
class MyViewController: UIViewController, EventsControllerDelegate {
  var client: ChatClient!
  var eventsController: EventsController!

  override func viewDidLoad() {
    super.viewDidLoad()
    eventsController = client.eventsController()
    eventsController.delegate = self
  }

  func eventsController(_ controller: EventsController, didReceiveEvent event: Event) {
    // Handle any event received
    switch event {
    case let event as MessageNewEvent:
      // handle MessageNewEvent
    default:
      break
    }
  }
}
// 2. Use the appropriate controller's delegate methods
// ChannelController delegate methods to listen Channel events
// CurrentUserController delegate methods to listen Current User events
/// * Delegates *

class ChannelViewController: ChatChannelControllerDelegate {
  func channelController(_ channelController: ChatChannelController, didUpdateMessages changes: [ListChange<ChatMessage>]) {
    // animate the changes to the message list
  }
}

let channelViewController = ChannelViewController()

channelController.delegate = channelViewController

/// * Combine *

channelController.messagesChangesPublisher
  .receive(on: RunLoop.main)
  .sink { changes in
    // animate the changes to the message list
  }
  .store(in: &cancellables)

channel.on("message.new").listen((Event event) {
 print("new message: ${event.message.text}");
});

channel.on("message.deleted").listen((Event event) {
 print("message ${event.message.id} was deleted");
});

ChannelClient channelClient = client.channel("messaging", "general");

// Subscribe for new message events
Disposable disposable = channelClient.subscribeFor(
    new Class[]{NewMessageEvent.class},
    event -> {
        NewMessageEvent newMessageEvent = (NewMessageEvent) event;
        Message message = newMessageEvent.getMessage();
    }
);

// Dispose when you want to stop receiving events
disposable.dispose();

// Subscribing via a UOBJECT member function
Channel->On<FMessageDeletedEvent>(this, &UMyObject::OnMessageDeleted);

// Subscribing via a lambda function
Channel->On<FMessageDeletedEvent>(
  [](const FMessageDeletedEvent& Event)
  {
    // Message was deleted
  });

// Get a single channel
var channel = await Client.GetOrCreateChannelWithIdAsync(ChannelType.Messaging, "my-channel-id");

// Or multiple with optional filters
var channels = await Client.QueryChannelsAsync(new List<IFieldFilterRule>()
{
  ChannelFilter.Members.In(Client.LocalUserData.User)
});

// Subscribe to events
channel.MessageReceived += OnMessageReceived;
channel.MessageUpdated += OnMessageUpdated;
channel.MessageDeleted += OnMessageDeleted;

channel.ReactionAdded += OnReactionAdded;
channel.ReactionUpdated += OnReactionUpdated;
channel.ReactionRemoved += OnReactionRemoved;

channel.MemberAdded += OnMemberAdded;
channel.MemberRemoved += OnMemberRemoved;
channel.MemberUpdated += OnMemberUpdated;

channel.MembersChanged += OnMembersChanged;
channel.VisibilityChanged += OnVisibilityChanged;
channel.MuteChanged += OnMuteChanged;
channel.Truncated += OnTruncated;
channel.Updated += OnUpdated;
channel.WatcherAdded += OnWatcherAdded;
channel.WatcherRemoved += OnWatcherRemoved;
channel.UserStartedTyping += OnUserStartedTyping;
channel.UserStoppedTyping += OnUserStoppedTyping;
channel.TypingUsersChanged += OnTypingUsersChanged;

You can also listen to all events at once:

channel.on((event) => {
  console.log("event", event);
  console.log("channel.state", channel.state);
});

val disposable: Disposable = channelClient.subscribe { event: ChatEvent ->
  when (event) {
    // Check for specific event types
    is NewMessageEvent -> {
      val message = event.message
    }
  }
}

// Dispose when you want to stop receiving events
disposable.dispose()

// There are 2 ways to listen for events
// 1. Use an EventsController
class MyViewController: UIViewController, EventsControllerDelegate {
  var client: ChatClient!
  var eventsController: EventsController!

  override func viewDidLoad() {
    super.viewDidLoad()
    eventsController = client.eventsController()
    eventsController.delegate = self
  }

  func eventsController(_ controller: EventsController, didReceiveEvent event: Event) {
    // Handle any event received
    switch event {
    case let event as MessageNewEvent:
      // handle MessageNewEvent
    default:
      break
    }
  }
}
// 2. Use the appropriate controller's delegate methods
// ChannelController delegate methods to listen Channel events
// CurrentUserController delegate methods to listen Current User events

channel.on().listen((Event event) {
 print("received a new event of type ${event.type}");
});

Disposable disposable = channelClient.subscribe(event -> {
    if (event instanceof NewMessageEvent) {
        Message message = ((NewMessageEvent) event).getMessage();
    }
});

// Dispose when you want to stop receiving events
disposable.dispose();

// Not supported in the Unreal SDK

// Not supported in the Unity SDK

Event Types

There are different type of events

User level/connection level events. You always receive these events.
Notification events you receive if you are a member of the channel
Channel level events you receive if you are watching the channel
User presence events are sent when you specify presence=true
Custom events. Your own pub/sub on top of the chat channel.

The example below shows how to watch a channel and enable user presence events. You can also watch channels and enable user presence when using query channels. See these links for more details on user presence, watching and query channels.

// Watch a channel with presence enabled to receive user presence events
const channel = client.channel("messaging", "my-conversation-123", {
  members: ["john", "jack"],
});

const state = await channel.watch({ presence: true });

// Listen for user presence changes
channel.on("user.presence.changed", (event) => {
  console.log(
    `${event.user.name} is now ${event.user.online ? "online" : "offline"}`,
  );
});

// Watch a channel with presence enabled
val watchRequest = WatchChannelRequest().apply {
  data["members"] = listOf("john", "jack")
  presence = true
}
channelClient.watch(watchRequest).enqueue { result ->
  if (result.isSuccess) {
    val channel: Channel = result.data()
  } else {
    // Handle result.error()
  }
}

// Subscribe to presence events
client.subscribeFor<UserPresenceChangedEvent> { event ->
  // Handle presence change
}

class PresenceObservingChannelVC: ChatChannelVC, EventsControllerDelegate {
  let eventsController: EventsController!

  override func viewDidLoad() {
    super.viewDidLoad()

    eventsController.delegate = self
  }

  func eventsController(_ controller: EventsController, didReceiveEvent event: Event) {
    if let event = event as? UserPresenceChangedEvent {
      showUser(event.user, isOnline: event.user.isOnline)
    }
  }
}

// Watch a channel with presence enabled to receive user presence events
final channel = client.channel(
  'messaging',
  id: 'my-conversation-123',
  extraData: {
    'members': ['john', 'jack'],
  },
);

await channel.watch({
  'presence': true,
});

// Listen for user presence changes
channel.on('user.presence.changed').listen((event) {
  print('${event.user?.name} is now ${event.user?.online == true ? "online" : "offline"}');
});

// Watch a channel with presence enabled
constexpr EChannelFlags AllFlags = EChannelFlags::Watch | EChannelFlags::State | EChannelFlags::Presence;
const FChannelProperties Properties{TEXT("messaging"), TEXT("my-conversation-123")};
Client->QueryChannel(Properties, AllFlags);

// Subscribe to presence events
Client->On<FUserPresenceChangedEvent>(
  [](const FUserPresenceChangedEvent& Event)
  {
    // Handle presence change
  });

// Watch a channel with presence enabled
WatchChannelRequest watchRequest = new WatchChannelRequest();
watchRequest.setPresence(true);
watchRequest.getData().put("members", Arrays.asList("john", "jack"));
channelClient.watch(watchRequest).enqueue(result -> {
  if (result.isSuccess()) {
    Channel channel = result.data();
  } else {
    // Handle result.error()
  }
});

// Subscribe to presence events
client.subscribeFor(
    new Class[]{UserPresenceChangedEvent.class},
    event -> {
      // Handle presence change
    }
);

// Get a channel
var channel = await Client.GetOrCreateChannelWithIdAsync(ChannelType.Messaging, "my-channel-id");

// Each user object exposes the PresenceChanged event
foreach (var member in channel.Members)
{
  member.User.PresenceChanged += (userObj, isOnline, isActive) =>
  {
    // Handle presence change
  };
}

Connection Events

The official SDKs make sure that a connection to Stream is kept alive at all times and that chat state is recovered when the user’s internet connection comes back online. Your application can subscribe to changes to the connection using client events.

client.on("connection.changed", (e) => {
  if (e.online) {
    console.log("the connection is up!");
  } else {
    console.log("the connection is down!");
  }
});

client.subscribeFor(
  ConnectedEvent::class,
  ConnectingEvent::class,
  DisconnectedEvent::class,
) { event ->
  when (event) {
    is ConnectedEvent -> {
      // Socket is connected
    }
    is ConnectingEvent -> {
      // Socket is connecting
    }
    is DisconnectedEvent -> {
      // Socket is disconnected
    }
  }
}

let connectionController = client.connectionController()

class ConnectionDelegate: ChatConnectionControllerDelegate {
  func connectionController(_ controller: ChatConnectionController,
               didUpdateConnectionStatus status: ConnectionStatus) {
     // handle connection change
  }
}

connectionController.delegate = ConnectionDelegate()

client.on('connection.changed', (e) {
  if (e.online) {
    print('the connection is up!');
  } else {
    print('the connection is down!');
  }
});

client.subscribeFor(
    new Class[]{ConnectedEvent.class, ConnectingEvent.class, DisconnectedEvent.class},
    event -> {
        if (event instanceof ConnectedEvent) {
            // Socket is connected
        } else if (event instanceof ConnectingEvent) {
            // Socket is connecting
        } else if (event instanceof DisconnectedEvent) {
            // Socket is disconnected
        }
    }
);

Client->On<FConnectionChangedEvent>(
  [](const FConnectionChangedEvent& Event)
  {
    if (Event.bOnline)
    {
      // Came online
    } else
    {
      // Went offline
    }
  });

public void SubscribeToConnectionEvents()
{
  Client.Connected += OnConnected;
  Client.Disconnected += OnDisconnected;
  Client.ConnectionStateChanged += OnConnectionStateChanged;
}

private void OnConnected(IStreamLocalUserData localUserData)
{
}

private void OnDisconnected()
{
}

private void OnConnectionStateChanged(ConnectionState previous, ConnectionState current)
{
}

Stop Listening for Events

It is a good practice to unregister event handlers once they are not in use anymore. Doing so will save you from performance degradations coming from memory leaks or even from errors and exceptions (i.e. null pointer exceptions)

// remove the handler from all client events
// const myClientEventListener = client.on('connection.changed', myClientEventHandler)
myClientEventListener.unsubscribe();

// remove the handler from all events on a channel
// const myChannelEventListener = channel.on('connection.changed', myChannelEventHandler)
myChannelEventListener.unsubscribe();

val disposable: Disposable = client.subscribe { /* ... */ }
disposable.dispose()

// There are 2 ways to listen for events
// 1. Use an EventsController
class MyViewController: UIViewController, EventsControllerDelegate {
  var client: ChatClient!
  var eventsController: EventsController!

  override func viewDidLoad() {
    super.viewDidLoad()
    eventsController = client.eventsController()
    eventsController.delegate = self

    // stop listening for events
    eventsController = nil
  }

  func eventsController(_ controller: EventsController, didReceiveEvent event: Event) {
    // Handle any event received
    switch event {
    case let event as MessageNewEvent:
      // handle MessageNewEvent
    default:
      break
    }
  }
}

final subscription = channel.on().listen((Event event) {
 print("received a new event of type ${event.type}");
});

subscription.cancel();

Disposable disposable = client.subscribe(event -> { /* ... */ });
disposable.dispose();

// Subscribe
const FDelegateHandle Handle = Client->On<FHealthCheckEvent>(this, &UMyObject::OnHealthCheck);

// Unsubscribe
const bool bSuccess = Client->Unsubscribe<FHealthCheckEvent>(Handle);

Client.Connected -= OnConnected;
Client.Disconnected -= OnDisconnected;
Client.ConnectionStateChanged -= OnConnectionStateChanged;

Custom Events

Custom events allow you to build your own pub/sub functionality on top of a channel. You can send any event with custom data and have it delivered to all users watching the channel.

To a channel

Users connected to a channel, either as a watcher or member, can send custom events and have them delivered to all users watching the channel.

// sends an event for the current user to all connect clients on the channel
await channel.sendEvent({
  type: "friendship_request",
  text: "Hey there, long time no see!",
});

// custom events can also be sent server-side, in that case a user must be included in the event payload
await channel.sendEvent({
  type: "friendship_request",
  text: "Hey there, long time no see!",
  user: user,
});

val channelClient = client.channel("messaging", "general")

// Send a custom event to all users watching the channel
channelClient.sendEvent(
  eventType = "friendship_request",
  extraData = mapOf("text" to "Hey there, long time no see!")
).enqueue { result ->
  if (result.isSuccess) {
    val chatEvent: ChatEvent = result.data()
  } else {
    // Handle result.error()
  }
}

// Subscribe for custom events
val disposable: Disposable = channelClient.subscribeFor<UnknownEvent> { customEvent ->
  val text = customEvent.rawData["text"]
}

// Dispose when you want to stop receiving events
disposable.dispose()

struct MyCustomEvent: CustomEventPayload {
  static let eventType: EventType = "my_custom_event"

  let text: String
}

// Send channel events using the channel controller
let event = MyCustomEvent(text: "This is my custom text")
channelController.eventsController().sendEvent(event)

// Subscribe for custom events works with delegation pattern
extension MyChannelViewModel: EventsControllerDelegate {

  private var eventsController: EventsController?

  func setupEventListening(channelController: ChatChannelController) {
    // eventsController needs to be retained (eg. class var)
    eventsController = channelController.eventsController()
    eventsController?.delegate = self
  }

  // EventsControllerDelegate method
  func eventsController(_: EventsController, didReceiveEvent event: Event) {
    // ignore regular events, we only care about custom channel event
    guard let channelEvent = event as? UnknownChannelEvent else {
      return
    }

    // Filter only `MyCustomEvent` event
    guard let customPayload = channelEvent.payload(ofType: MyCustomEvent.self) else {
      return
    }

    print("Received a custom event with text \(myCustomPayload.text)")
  }
}

// sends an event for the current user to all connect clients on the channel
await channel.sendEvent(
  Event(
   type: 'friendship_request',
   extraData: {
    'text': 'Hey there, long time no see!',
   },
  ),
);

Map<Object, Object> extraData = new HashMap<>();
extraData.put("text", "Hey there, long time no see!");

// Send a custom event to all users watching the channel
channelClient.sendEvent("friendship_request", extraData).enqueue(result -> {
  if (result.isSuccess()) {
    ChatEvent chatEvent = result.data();
  } else {
    // Handle result.error()
  }
});

// Custom events must be defined as a USTRUCT with a static FName member `StaticType`:
USTRUCT()
struct FMyCustomEvent
{
  GENERATED_BODY()

  inline static FName StaticType = TEXT("my_custom_event");

  // Custom members must be UPROPERTYs to be picked up by the serializer
  UPROPERTY()
  float MyCustomData;
};

// Send the custom event
Channel->SendEvent(FMyCustomEvent{5000.f});

$channel->sendEvent(["type" => "friendship_request", "text" => "Hey there, long time no see!"], $serverUser["id"]);

channel.send_event({"type": "friendship_request", "text": "Hey there, long time no see!"}, server_user["id"])

# require 'stream-chat'

channel.send_event({type: "friendship_request", text: "Hey there, long time no see!"}, server_user["id"]

var channelEvent = new Event { Type = "friendship_request", UserId = serverUser.Id };
channelEvent.SetData("text", "Hey there, long time no see!");
await eventClient.SendEventAsync("channel-type", "channel-id", channelEvent);

ch.SendEvent(context.Background(), &Event{
	Type:   "friendship_request",
	ExtraData: map[string]interface{}{"text": "Hey there, long time no see!"},
}, "userId")

// Not yet supported in the Unity SDK

Custom events are enabled by default on all channel types, you can disable them using the Dashboard or the API the same way as you would manage other channel features (ie. replies, URL previews, …)

Permissions

Like every client-side API request, sending a custom event includes a permission check. By default users that can read messages on a channel can also send custom events. Check the Auth & Permission section to find out more about how permissions can be customized for your application.

Keep in mind a clever user can send their own custom events. We recommend using the type attribute or custom data on the event to limit the kinds of events that are displayed to the recipient to ones that are safe e.g. if a bad actor sends a “password reset” or other malicious events, your client app should just ignore it.

To a user

This allows you to send custom events to a connected user. The event is delivered to all connected clients for that user.

It is only available with server-side authentication. A copy of the event is sent via web-hooks if it is enabled.

await client.sendUserCustomEvent(targetUserID, {
  type: "friendship_request",
  text: "Tommaso wants to be your friend",
});

ev := UserCustomEvent{
	Type: "friendship_request",
	ExtraData: map[string]interface{}{
		"text":  "Tommaso wants to be your friend",
	},
}

err := client.SendUserCustomEvent(targetUserID, &ev)

$client->sendCustomEvent($user["id"], ["type" => "friendship_request", "text" => "Tommaso wants to be your friend"]);

Event.sendUserCustom(user.getId())
  .event(
    EventUserCustomRequestObject.builder()
      .type("friendship_request")
      .additionalField("text", "Tommaso wants to be your friend")
      .build())
  .request();

client.send_user_custom_event(
  server_user["id"], {"type": "friendship_request", "text": "Tommaso wants to be your friend"}
)

client.send_user_event(server_user[:id], { event: { type: 'friendship_request', text: 'Tommaso wants to be your friend' } })

var customEvent = new UserCustomEvent { Type = "friendship_request" };
customEvent.SetData("text", "Tommaso wants to be your friend");
await eventClient.SendUserCustomEventAsync(user.Id, customEvent);

// Not yet supported in the Unity SDK

name	type	description	default
targetUserID	string	target user ID	-
data	object	event to be sent	-
data.type	string	type of the event	-

If the user doesn’t exist, a 404 Not Found error is returned.

The type of the event shouldn’t contain any . character otherwise a 400 Bad Request error is returned. This is a character used for built-in events, see the Built-in Events section below for more details.

Event Object

name	type	description	optional
cid	string	Channel ID	✓
type	string	Event type
message	object	Message Object	✓
reaction	object	Reaction Object	✓
channel	object	Channel Object	✓
member	object	User object for the channel member that was added/removed	✓
user	object	User object of the current user	✓
me	object	User object of the health check user	✓
total_unread_count	int	the number of unread messages for current user	✓
watcher_count	int	Number of users watching this channel	✓

Built-in Events

The table below shows an overview of all built-in events:

Event	Trigger	Recipients	Type
channel.deleted	when a channel is deleted	clients watching the channel	channel event
channel.hidden	when a channel is marked as hidden	clients from the user that marked the channel as hidden (see hiding channels)	channel event
channel.truncated	when a channel’s history is truncated	clients watching the channel	channel event
channel.updated	when a channel is updated	clients watching the channel	channel event
channel.visible	when a channel is made visible	clients from the user that marked the channel as visible (see hiding channels)	channel event
connection.changed	when the state of the connection changed	local event	client event
connection.recovered	when the connection to chat servers is back online	local event	client event
health.check	every 30 seconds to confirm that the client connection is still alive	all clients	client event
member.added	when a member is added to a channel	clients watching the channel	channel event
member.removed	when a member is removed from a channel	clients watching the channel	channel event
member.updated	when a channel member is updated (promoted to moderator/accepted/rejected the invite)	clients watching the channel	channel event
message.deleted	when a message is deleted	clients watching the channel	channel event
message.new	when a new message is added on a channel	clients watching the channel	channel event
message.read	when a channel is marked as read	clients watching the channel	channel event
message.updated	when a message is updated	clients watching the channel	channel event
notification.added_to_channel	when the user is added to the list of channel members	clients from the user added that are not watching the channel	notification event
notification.channel_deleted	when a channel is deleted	clients from members that are not watching the channel	notification event
notification.channel_mutes_updated	when a channel is muted	clients from the user that muted the channel	notification event
notification.channel_truncated	when a channel’s history is truncated	clients from members that are not watching the channel	notification event
notification.invite_accepted	when the user accepts an invite	clients from the user invited that are not watching the channel	notification event
notification.invite_rejected	when the user rejects an invite	clients from the user invited that are not watching the channel	notification event
notification.invited	when the user is invited to join a channel	clients from the user invited that are not watching the channel	notification event
notification.mark_read	when the total count of unread messages (across all channels the user is a member) changes	clients from the user with the new unread count	notification event
notification.mark_unread	when the user marks a message as unread	clients from the user with the new unread count	notification event
notification.message_new	when a message is added to a channel	clients that are not currently watching the channel	notification event
notification.mutes_updated	when the user mutes are updated	clients from the user that updated the list of mutes	notification event
notification.removed_from_channel	when a user is removed from the list of channel members	clients from the user removed that are not watching the channel	notification event
reaction.deleted	when a message reaction is deleted	clients watching the channel	channel event
reaction.new	when a message reaction is added	clients watching the channel	channel event
reaction.updated	when a message reaction is updated	clients watching the channel	channel event
typing.start	when a user starts typing	clients watching the channel	channel event
typing.stop	when a user stops typing	clients watching the channel	channel event
user.banned	when the user is banned	clients for the banned user	client event
user.deleted	when a user is deleted	clients subscribed to the user status	user presence event
user.messages.deleted	when the user’s messages are deleted	clients for the banned user	client event
user.messages.deleted	when the user’s messages are deleted	clients watching the channel where the user was banned	channel event
user.presence.changed	when a user status changes (eg. online, offline, away, etc.)	clients subscribed to the user status	user presence event
user.unbanned	when the user ban is lifted	clients for the banned user	client event
user.updated	when a user is updated	clients subscribed to the user status	user presence event
user.watching.start	when a user starts watching a channel	clients watching the channel	channel event
user.watching.stop	when a user stops watching a channel	clients watching the channel	channel event

Overview

Unread Counts