# Join multiple channels (/en/realtime-media/rtc/build/join-and-manage-channels/join-multiple-channels/macos)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

Agora RTC SDK enables you to simultaneously join multiple channels. This capability allows you to receive and publish audio and video streams across multiple channels concurrently.

      
  
      
  
      
## Understand the tech

RTC SDK's multi-channel functionality is based on two key components:

* `AgoraRtcConnection`

  The `AgoraRtcConnection` object identifies a connection. It contains the following information:

  * Channel name
  * User ID of the local user

  You create multiple `AgoraRtcConnection` objects, each with a different channel name and user ID. Each `AgoraRtcConnection` instance can independently publish multiple audio streams and a single video stream.

* `AgoraRtcEngineKit(Ex)`

  The class contains methods tailored for interacting with a designated `AgoraRtcConnection` object.

  To join multiple channels, you call `joinChannelExByToken` method in the `AgoraRtcEngineKit(Ex)` class multiple times, using a different `AgoraRtcConnection` instance each time.

When joining multiple channels:

* Ensure that the user ID for each `AgoraRtcConnection` object is unique and nonzero.

* Configure publishing and subscribing options for the `AgoraRtcConnection` object in `joinChannelExByToken`.

* Pass the `AgoraRtcEngineDelegate` object to the `delegate` parameter when calling the `joinChannelExByToken` method to receive multiple channel-related event notifications.

## Prerequisites

Ensure that you have implemented the [SDK quickstart](/en/realtime-media/rtc/get-started-sdk) in your project.

## Implementation

This section explains how to join a second channel as a host after you have already joined the first channel.

1. Define an `AgoraRtcConnection` object in your project's `ViewController.swift` file.

   ```swift
   let connection1 = AgoraRtcConnection()
   ```

2. Join the channel using a random user ID.

   ```swift
   var mediaOptions = AgoraRtcChannelMediaOptions()
   mediaOptions.autoSubscribeVideo = .of(true)
   mediaOptions.autoSubscribeAudio = .of(true)
   connection1.channelId = channelName1
   connection1.localUid = UInt.random(in: 1001...2000)
   var result = agoraKit.joinChannelEx(byToken: "your token", connection: connection1, delegate: channel1, mediaOptions: mediaOptions, joinSuccess: nil)
   channel1.channelId = channelName1
   channel1.connectionDelegate = self
   if result != 0 {
     self.showAlert(title: "Error", message: "joinChannel1 call failed: \(result), please check your params")
   }
   ```

3. Set up the remote video in the `didJoinedOfUid` callback.

   ```swift
   func rtcEngine(_ engine: AgoraRtcEngineKit, channelId: String, didJoinedOfUid uid: UInt, elapsed: Int) {
     LogUtils.log(message: "remote user join: \(uid) \(elapsed)ms", level: .info)
     // In this operation, only one remote video view is available
     // Here, we check if there's a view tagged with that UID
     let videoCanvas = AgoraRtcVideoCanvas()
     videoCanvas.uid = uid
     // The view to be bound
     videoCanvas.view = channelId == channelName1 ? channel1RemoteVideo.videoView : channel2RemoteVideo.videoView
     videoCanvas.renderMode = .hidden
     let connection = AgoraRtcConnection()
     agoraKit.setupRemoteVideoEx(videoCanvas, connection: connection)
   }
   ```

## Reference

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

### Sample project

Agora offers the [JoinMultiChannels](https://github.com/AgoraIO/API-Examples/tree/main/macOS/APIExample/Examples/Advanced/JoinMultiChannel) open-source sample project for your reference. Download the project or view the source code for a more detailed example.

### API reference

* [`AgoraRtcEngineKit`](https://api-ref.agora.io/en/video-sdk/macos/4.x/documentation/agorartckit/agorartcenginekit)
* [`AgoraRtcConnection`](https://api-ref.agora.io/en/video-sdk/macos/4.x/documentation/agorartckit/agorartcconnection)
* [`joinChannelExByToken` \[1/2\]](https://api-ref.agora.io/en/video-sdk/macos/4.x/documentation/agorartckit/agorartcenginekit/joinchannelex%28bytoken\:channelid\:useraccount\:delegate\:mediaoptions\:joinsuccess:%29)
* [`setupRemoteVideoEx`](https://api-ref.agora.io/en/video-sdk/macos/4.x/documentation/agorartckit/agorartcenginekit/setupremotevideoex%28_\:connection:%29)