Live audio streaming is increasingly popular across a wide range of uses, from live podcasts and interviews to live music performances. The possibilities are endless once you have a few users engaging with an audience in real-time.

There’s an easy way to accomplish live audio streaming using the Agora React Native SDK. In this tutorial, we’ll walk through building a live audio broadcasting app that can have multiple broadcasters and host thousands of users by utilizing the Agora Audio SDK. We’ll go over the structure, setup, and execution of the app before diving into the code. The open-source code is available here

We’ll be using Agora RTC SDK for React Native for the example. I’m using v3.2.2 at the time of writing.

Creating an Agora Account

Sign up at https://console.agora.io/ and log in to the dashboard.

Navigate to the Project List tab under the Project Management tab and create a project by clicking the blue Create button.

Create a project and retrieve the App ID. (When prompted to use App ID + Certificate, select only App ID.) The App ID will be used to authorize your requests while you’re developing the application, without generating tokens.

Note: This guide does not implement token authentication which is recommended for all RTE apps running in production environments. For more information about token-based authentication within the Agora platform please refer to this guide: https://docs.agora.io/en/Video/token?platform=All%20Platforms

Structure of Our Example

This is the structure of the application:

.
├── android
├── components
│ └── Permission.ts
│ └── Style.ts
├── ios
├── App.tsx
├── index.js
.

Running the App

You’ll need to have a recent version of Node.js and NPM installed;

• Make sure you’ve set up an Agora account, set up a project, and generated an App ID (as discussed above).
• Download and extract the ZIP file from the master branch.
• Run npm install to install the app dependencies in the unzipped directory.
• Navigate to ./App.tsx and enter the App ID as appId: YourAppIdHere in the state declaration.
• If you’re building for iOS, open a terminal and execute cd ios && pod install.
• Connect your device, and run npx react-native run-android / npx react-native run-ios to start the app. Give it a few minutes to build the app and install it on your device.
• Once you see the home screen on your mobile device (or emulator), click the start call button on the device.

That’s it. You should have an audio broadcast going between the two devices.

The app uses channel-x as the channel name.

Before we dive into the code, let’s get a few basics out of the way:

• We’ll use the Agora RTC (Real-time Communication) SDK to connect to a channel and join an audio call.
• We can have multiple users broadcasting to a channel. All users as an audience on that channel can listen to the broadcasters.
• The audience can dynamically switch to a broadcaster role.
• The Agora RTC SDK uses unique IDs (UIDs) for each user. To associate these UIDs with a username, we’ll use the Agora RTM (Real-time Messaging) SDK to signal the username to others on the call. We’ll discuss how it’s done below. Let’s take a look at how the code works:

App.tsx

App.tsx will be the entry point into the app. We’ll have all our code in this file. When you open the app, there will be a username field with three buttons: to join the call, end the call, and toggle our user role between broadcaster and audience.

We start by writing the used import statements. Next, we define an interface for our application state containing the following:
appId: our Agora App ID
token: token generated to join the channel
isHost: boolean value to switch between audience and broadcaster
channelName: name for the channel
joinSucceed: boolean value to store if we’ve connected successfully
rtcUid: local user’s UID on joining the RTC channel
myUsername: local user’s name to log in to RTM
usernames: a dictionary associating RTC UIDs of remote users to their usernames that we’ll get using RTM
peerIds: an array to store the UIDs of other users in the channel

We define a class-based component: the _rtcEngine variable will store the instance of the RtcEngine class, and the _rtmEngine variable will store the instance of the RtmEngine class, which we can use to access the SDK functions.

In the constructor, we set our state variables and request permission for recording audio on Android. (We use a helper function from permission.ts, as described below.) When the component is mounted, we call the initRTC and initRTM functions, which initialize the RTC and RTM engines using the App ID. When the component unmounts, we destroy our engine instances.

RTC Initialization

The RTC triggers a userJoined event for each user present when we join the channel and for each new user who joins later. The userOffline event is triggered when a user leaves the channel. We use event listeners to sync our peerIds array.

Note: Audience members don’t trigger the userJoined/userOffline event.

RTM Initialization

We’re using RTM to send our username to other usernames on the call. And this is how we associate our usernames with our RTC UID

• When a user joins a channel, we send a message to all channel members as UID:Username.
• On receiving a channel message, all users add the key-value pair to their username dictionary.
• When a new user joins, all members on the channel send a peer message to that user in the same schema UID:Username.
• On receiving peer messages, we do the same (add the key-value pair to the dictionary) and update our usernames.
  Following our plan, we attach event listeners with functions to populate and update usernames on channelMessageReceived (broadcast message to channel), messageReceived (peer message), and channelMemberJoined events. We also create a client on the engine using the same App ID.

Functions for Our Buttons

Rendering Our UI

Permission.ts

Style.ts

Conclusion

That’s how easy it is to build a live audio streaming app. For more information about building applications using Agora SDKs, take a look at the Agora Video Call Quickstart Guide and Agora API Reference.

I invite you to join the Agora Developer Slack community. You can ask any questions about Agora in the #react-native-help-me channel.