Stream channels

Stream channels are based on the room model. In Signaling, communication through stream channels requires use of specific APIs. This page shows you how to join, leave, and send messages in stream channels.

Understand the tech

To use stream channels, you first create a stream channel object instance. The channel instance gives you access to all stream channel management methods. Use the stream channel instance to:

Join and leave a channel
Join and leave topics
Subscribe to and unsubscribe from topics
Send messages
Destroy the channel instance

After joining a stream channel, you listen to event notifications in the channel. To send and receive messages in the channel, you use topics. Signaling allows thousands of stream channels to exist simultaneously in your app. However, due to client-side performance and bandwidth limitations, a single client may only join a limited number of channels concurrently. For details, see API usage restrictions.

Prerequisites

Ensure that you have:

Integrated the Signaling SDK in your project, and implemented the framework functionality from the SDK quickstart page.
Activated stream channel capability in Agora Console. To do so, go to Projects > Edit project > All features > Signaling > Stream channel configuration and toggle to enable.

Implement communication in a stream channel

This section shows you how to use the Signaling SDK to implement stream channel communication in your app.

Create a stream channel

To use stream channel functionality, call createStreamChannel to create a StreamChannel object instance.

StreamChannel mStreamChannel = mRtmClient.createStreamChannel("chat_room");

This method creates only one StreamChannel instance at a time. If you need to create multiple instances, call the method multiple times.

// Create the first instance
StreamChannel mStreamChannel1 = mRtmClient.createStreamChannel("chat_room1");
// Create the second instance
StreamChannel mStreamChannel2 = mRtmClient.createStreamChannel("chat_room2");

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Signaling enables you to create unlimited stream channel instances in a single app. However, best practice is to create channels based on your actual requirements to maintain optimal client-side performance. For instance, if you hold multiple stream channel instances, destroy the ones that are no longer in use to prevent resource blocking, and recreate them when they are needed again.

Join a stream channel

Call the join method on the StreamChannel instance with appropriate options as follows:

JoinChannelOptions options = new JoinChannelOptions();
options.setToken("your_token");
options.setWithPresence(true);
options.setWithLock(true);
options.setWithMetadata(true);
mStreamChannel.join(options, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "join stream channel success");
    }
    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

When joining a channel, set the token parameter in JoinChannelOptions with a temporary token from Agora Console.

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To facilitate testing of the app during development, set the Authentication mechanism to Debugging mode when creating the project, and use the app ID in the token parameter when joining a channel.

JoinChannelOptions options = new JoinChannelOptions("your_appid", true, true, true);
mStreamChannel.join(options, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "join stream channel success");
    }
    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

In stream channels, message flow is managed using topics. Even if you configure a global message listener, you must still join a topic to send messages. Similarly, to receive messages you must subscribe to a topic. See Topics for more information.

Send a message

To send a message to a stream channel, you first need to:

Create a StreamChannel instance.
Use the join method to join a channel.
Call joinTopic to register as a message publisher for the specified topic. See Topics.

Call publishTopicMessage to publish a message to a topic. This method sends a message to a single topic at a time. To deliver messages to multiple topics, call the method separately for each topic.

Refer to the following sample code for sending messages:

String message

_18// Send a string message _18String message = "Hello Agora!"; // Message content _18String topicName = "chat_topic"; // Topic name for publishing _18var options = new TopicMessageOptions(); // Topic message sending options _18options.customType = "PlainTxt"; // Set a custom type for the message _18mStreamChannel.publishTopicMessage(topicName, message, options, new ResultCallback<Void>() { _18 @Override _18 public void onSuccess(Void responseInfo) { _18 // Log success _18 log(CALLBACK, "publish topic message success"); _18 } _18 _18 @Override _18 public void onFailure(ErrorInfo errorInfo) { _18 // Log failure _18 log(ERROR, errorInfo.toString()); _18 } _18});
Binary message

_18// Send a binary message _18byte[] message = new byte[] { 00, 01, 35, 196 }; // Binary message content _18String topicName = "chat_topic"; // Topic name for publishing _18var options = new TopicMessageOptions(); // Topic message sending options _18options.customType = "ByteArray"; // Set a custom type for the message _18mStreamChannel.publishTopicMessage(topicName, message, options, new ResultCallback<Void>() { _18 @Override _18 public void onSuccess(Void responseInfo) { _18 // Log success _18 log(CALLBACK, "publish topic message success"); _18 } _18 _18 @Override _18 public void onFailure(ErrorInfo errorInfo) { _18 // Log failure _18 log(ERROR, errorInfo.toString()); _18 } _18});

In Signaling, a user may register as a message publisher for up to 8 topics concurrently. However, there are no limitations on the number of users a single topic can accommodate. You can achieve a message transmission frequency to a topic of up to 120 QPS. This capability is useful in scenarios that demand high-frequency and high-concurrency data processing, such as Metaverse location status synchronization, collaborative office sketchpad applications, and parallel control operation-instructions transmission.

Leave a stream channel

To leave a channel, call the leave method on the StreamChannel instance:

mStreamChannel.leave(new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "leave stream channel success");
    }
    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

To rejoin a stream channel, call the join method again. You can join and leave as long as the corresponding StreamChannel instance remains active and has not been destroyed.

Destroy the stream channel instance

To destroy a stream channel instance, call release:

mStreamChannel.release();

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Destroying a stream channel removes the StreamChannel instance from your app. This action is local to your app and does not affect other users or the Signaling channel.

Reference

This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

Message packet size

Signaling SDK imposes size limits on message payload packets sent in Message channels and Stream channels. The limit is 32 KB for Message channels and 1 KB for Stream channels. The message payload packet size includes the message payload itself plus the size of the customType field. If the message payload package size exceeds the limit, you receive an error message.

// ErrorInfo
ErrorInfo {
    errorCode = -11010;
    reason = "Publish too long message.";
    operation = "publishTopicMessage"; // or "publish"
}

To avoid sending failure due to message payload packet size exceeding the limit, check the packet size before sending.