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Signaling Quickstart

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Rapidly develop your first Signaling app.

Use Signaling SDK to add low-latency, high-concurrency signaling and synchronization capabilities to your app.

Signaling also helps you enhance the user experience in Video Calling, Voice Calling, Interactive Live Streaming, and Broadcast Streaming applications.

This page shows you how to use the Signaling SDK to rapidly build a simple application that sends and receives messages. It shows you how to integrate the Signaling SDK in your project and implement pub/sub messaging through Message channels. To get started with stream channels, follow this guide to create a basic Signaling app and then refer to the Stream channels guide.

Understand the tech

To use Signaling features in your app, you initialize a Signaling client instance and add event listeners. To connect to Signaling, you login using an authentication token. To send a message to a message channel, you publish the message. Signaling creates a channel when a user subscribes to it. To receive messages other users publish to a channel, your app listens for events.

To create a pub/sub session for Signaling, implement the following steps in your app:

Prerequisites

To implement the code presented on this page you need to have:

  • An Agora account and project.

  • Enabled Signaling in Agora Console

  • Flutter 2.0.0 or higher

  • Dart 2.15.1 or higher

  • Android Studio, IntelliJ, VS Code, or any other IDE that supports Flutter, see Set up an editor.

  • If your target platform is iOS:

    • Xcode on macOS (latest version recommended)
    • A physical iOS device
    • iOS version 12.0 or later

  • If your target platform is Android:

    • Android Studio on macOS or Windows (latest version recommended)
    • An Android emulator or a physical Android device.

  • If you are developing a desktop application for Windows, macOS or Linux, make sure your development device meets the Flutter desktop development requirements.

  • Ensure that a firewall is not blocking your network communication.

Signaling 2.x is an enhanced version compared to 1.x with a wide range of new features. It follows a new pricing structure. See Pricing for details.

Project setup

To create a new Flutter project, follow these steps:

  1. Open a terminal and execute the following command:

    flutter create sdk_quickstart

  2. Open the project in your IDE. Add the Signaling SDK dependency to pubspec.yaml under dependencies:

    dependencies:
# Add the Signaling SDK dependency, use the latest version number
  agora_rtm: ^2.2.1

    To integrate Signaling SDK version 2.2.1 or above, and Video SDK version 4.3.0 or above at the same time, refer to handle integration issues.

  3. To install the dependencies, open the terminal and execute the following command in the project path:

    flutter pub get

  4. To create a basic template for your project, open main.dart, delete the contents of the file, and paste the following code:

    import 'package:agora_rtm/agora_rtm.dart';
import 'package:flutter/material.dart';
import 'dart:convert';

void main() async {
    // Wait for Widgets to be initialized.
    WidgetsFlutterBinding.ensureInitialized();

    // Create a Signaling client instance

    // Login to Signaling

    // Subscribe to a channel

    // Publish messages

    // Unsubscribe from a channel

    // Logout from Signaling

}

Implement Signaling

A complete code sample that implements the basic features of Signaling is presented here for your reference. To use the sample code, copy the following lines into the lib/main.dart file.

Complete sample code

import 'package:flutter/material.dart';
import 'package:agora_rtm/agora_rtm.dart';
import 'dart:convert';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  const userId = 'your_userId';
  const appId = 'your_appId';
  const token = 'your_token';
  const channelName = 'getting-started';
  late RtmClient rtmClient;

  // Create a Signaling client instance
  try {
    // Create rtm client
    final (status, client) = await RTM( appId, userId);
    if (status.error == true) {
        print('\${status.operation} failed due to \${status.reason}, error code: \${status.errorCode}');
    } else {
        rtmClient = client;
        print('Initialize success!');
    }

    // Add events listener
    rtmClient.addListener(
    // Add message event handler
    message: (event) {
      print('received a message from channel: \${event.channelName}, channel type : \${event.channelType}');
      print('message content: \${utf8.decode(event.message!)}, custom type: \${event.customType}');
    },
    // add link state event handler
    linkState: (event) {
      print('link state changed from \${event.previousState} to \${event.currentState}');
      print('reason: \${event.reason}, due to operation \${event.operation}');
    });
  } catch (e) {
    print('Initialize failed!:\${e}');
  }

  // Login to Signaling
  try {
    // login rtm service
    var (status,response) = await rtmClient.login(token);
    if (status.error == true) {
        print('\${status.operation} failed due to \${status.reason}, error code: \${status.errorCode}');
    } else {
        print('login RTM success!');
    }
  } catch (e) {
    print('Failed to login: $e');
  }

  // Subscribe to a channel
  try {
    var (status,response) = await rtmClient.subscribe(channelName);
    if (status.error == true) {
        print('\${status.operation} failed due to \${status.reason}, error code: \${status.errorCode}');
    } else {
        print('subscribe channel: \${channelName} success!');
    }
  } catch (e) {
    print('Failed to subscribe channel: $e');
  }

  // Publish messages
  // Send a message every second for 100 seconds
  for (var i = 0; i < 100; i++) {
    try {
      var (status, response) = await rtmClient.publish(
          channelName,
          'message number : $i',
          channelType: RtmChannelType.message,
          customType: 'PlainText'
          );
      if (status.error == true ){
        print('\${status.operation} failed, errorCode: \${status.errorCode}, due to \${status.reason}');
      } else {
        print('\${status.operation} success! message number:$i');
      }
    } catch (e) {
      print('Failed to publish message: $e');
    }
    await Future.delayed(Duration(seconds: 1));
  }

  // Unsubscribe from a channel
  try {
    var (status,response) = await rtmClient.unsubscribe(channelName);
    if (status.error == true) {
        print('\${status.operation} failed due to \${status.reason}, error code: \${status.errorCode}');
    } else {
        print('unsubscribe success!');
    }
  } catch (e) {
    print('something went wrong with logout: $e');
  }

  // Logout of Signaling
  try {
    // logout rtm service
    var (status,response) = await rtmClient.logout();
    if (status.error == true) {
        print('\${status.operation} failed due to \${status.reason}, error code: \${status.errorCode}');
    } else {
        print('logout RTM success!');
    }
  } catch (e) {
    print('something went wrong with logout: $e');
  }
}

Follow the implementation steps to understand the core API calls in the sample code or to build the demo step-by-step.

Initialize the Signaling engine

Before calling any other Signaling SDK API, initialize an RtmClient object instance. Add the following code to the lib/main.dart file.

import 'package:agora_rtm/agora_rtm.dart';
import 'package:flutter/material.dart';
import 'dart:convert';

void main() async {
  // Wait for Widgets to be initialized.
  WidgetsFlutterBinding.ensureInitialized();

  const userId = 'your_userId';
  const appId = 'your_appId';
  const token = 'your_token';
  const channelName = 'getting-started';
  late RtmClient rtmClient;

  try {
    // Create rtm client
    final (status, client) = await RTM( appId, userId);
    if (status.error == true) {
        print('${status.operation} failed due to ${status.reason}, error code: ${status.errorCode}');
    } else {
        rtmClient = client;
        print('Initialize success!');
    }
  // Add events listener

  } catch (e) {
    print('Initialize failed!:${e}');
  }
}

Add an event listener

The event listener enables you to implement the processing logic in response to Signaling events. Use the following code to handle event notifications or display received messages:

// Paste the following code snippet below the "add event listener" comment
rtmClient.addListener(
  // Add message event handler
  message: (event) {
    print('received a message from channel: ${event.channelName}, channel type : ${event.channelType}');
    print('message content: ${utf8.decode(event.message!)}, custome type: ${event.customType}');
  },
  // Add linkState event handler
  linkState: (event) {
    print('link state changed from ${event.previousState} to ${event.currentState}');
    print('reason: ${event.reason}, due to operation ${event.operation}');
  });

Log in to Signaling

To connect to Signaling and access Signaling network resources, such as sending messages, and subscribing to channels, call login.

During a login operation, the client attempts to establish a connection with Signaling. Once the connection is established, the client transmits heartbeat information to the Signaling server at fixed intervals to keep the client active until the client actively logs out or is disconnected. The connection is interrupted when timeout occurs. During this period, users may freely access the Signaling network resources subject to their own permissions and usage restrictions.

// Paste the following code snippet below "Login to Signaling" comment
try {
  // Login to Signaling
  var (status,response) = await rtmClient.login(token);
  if (status.error == true) {
      print('${status.operation} failed due to ${status.reason}, error code: ${status.errorCode}');
  } else {
      print('login RTM success!');
  }
} catch (e) {
  print('Failed to login: $e');
}

Send a message

To distribute a message to all subscribers of a message channel, call publish. The following code sends a string type message every second for 100 seconds.

// Paste the following code snippet below the "Publish messages" comment
// Send a message every second for 100 seconds
for (var i = 0; i < 100; i++) {
  try {
    var (status, response) = await rtmClient.publish(
        channelName,
        'message number : $i',
        channelType: RtmChannelType.message,
        customType: 'PlainText'
        );
    if (status.error == true ){
      print('${status.operation} failed, errorCode: ${status.errorCode}, due to ${status.reason}');
    } else {
      print('${status.operation} success! message number:$i');
    }
  } catch (e) {
    print('Failed to publish message: $e');
  }
  await Future.delayed(Duration(seconds: 1));
}

Subscribe and unsubscribe

To receive messages sent to a channel, call subscribe to subscribe to channel messages:

// Paste the following code snippet below the "Subscribe to a channel" comment
try {
  // Subscribe to a channel
  var (status,response) = await rtmClient.subscribe(channelName);
  if (status.error == true) {
      print('${status.operation} failed due to ${status.reason}, error code: ${status.errorCode}');
  } else {
      print('subscribe channel: ${channelName} success!');
  }
} catch (e) {
  print('Failed to subscribe channel: $e');
}

When you no longer need to receive messages from a channel, unsubscribe from the channel:

// Paste the following code snippet below the "Unsubscribe from a channel" comment
try {
  // Unsubscribe from a channel
  var (status,response) = await rtmClient.unsubscribe(channelName);
  if (status.error == true) {
      print('${status.operation} failed due to ${status.reason}, error code: ${status.errorCode}');
  } else {
      print('unsubscribe success!');
  }
} catch (e) {
  print('something went wrong with logout: $e');
}

For more information about subscribing and sending messages, see Message channels and Stream channels.

Log out of Signaling

When a user no longer needs to use Signaling, call logout. Logging out means closing the connection between the client and Signaling. The user is automatically logged out or unsubscribed from all message and stream channels. Other users in the channel receive an onPresenceEvent notification of the user leaving the channel.

// Paste the following code snippet below the "Log out of Signaling" comment
try {
  // Log out of Signaling
  var (status,response) = await rtmClient.logout();
  if (status.error == true) {
      print('${status.operation} failed due to ${status.reason}, error code: ${status.errorCode}');
  } else {
      print('logout RTM success!');
  }
} catch (e) {
  print('something went wrong with logout: $e');
}

Test Signaling

Take the following steps to test the sample code:

  1. Use the Token Builder to generate a Signaling token:

    1. Select Signaling from the Agora products dropdown.
    2. Fill in your app ID and app certificate from Agora Console. Leave the remaining fields blank.
    3. Click Generate Token.

  2. In your code, replace your_appId with your app ID from Agora Console, your_userId with a numeric string and your_token with the generated token.

  3. Save the project.

  4. Connect the target device to your computer, or open the device emulator.

  5. In the terminal, execute the following command in the project path to run the sample project on the target device:

    flutter run

    You see the following output in the terminal:

    flutter: publish success! message number:0
flutter: publish success! message number:1
flutter: publish success! message number:2
flutter: publish success! message number:3

  6. Run a second instance of the project on another device or emulator using a different userId.

    You see the following notifications for messages sent from the first app instance:

    flutter: received a message from channel: getting-started, channel type : RtmChannelType.message
flutter: message content: message number : 0, custom type: PlainText
flutter: received a message from channel: getting-started, channel type : RtmChannelType.message
flutter: message content: message number : 1, custom type: PlainText

Reference

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

Token authentication

In this guide you retrieve a temporary token from a Token Builder. To understand how to create an authentication server for development purposes, see Secure authentication with tokens.

Sample project

Agora provides an open source sample project on GitHub for your reference. Download it or view the source code for a more detailed example.

API reference

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