# Use tokens (/en/realtime-media/rtc/build/authenticate-users/authentication-workflow/ios)

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

To protect your business, it is best practice to authenticate every client that joins a channel. This guide explains how to fetch an authentication token from your token server, use it to join a channel, and renew the token when it expires.

## Understand the tech

When a user attempts to connect to an Agora channel, your app retrieves a token from the token server in your security infrastructure. Your app then sends this token to Agora SDRTN® for authentication. Agora SDRTN® reads the information stored in the token to validate the request.

The following figure shows the call flow you implement to create step-up-authentication with Agora Video Calling:

<Accordions>
  <Accordion title="Token authentication flow">
    ![token authentication flow](https://assets-docs.agora.io/images/video-sdk/token-authentication.svg)
  </Accordion>
</Accordions>

## Prerequisites

Before starting, ensure that you have:

* Implemented the [Quickstart](/en/realtime-media/rtc/get-started-sdk) in your project.

* Deployed a token server using either of the following guides:

  * [Deploy a token server](/en/realtime-media/rtc/build/authenticate-users/deploy-token-server)
  * [Deploy a middleware server](/en/realtime-media/rtc/build/authenticate-users/middleware-token-server)

## Implement basic authentication

This section shows you how to implement basic authentication by acquiring a token and using it to join a channel.

      
  
      
  
      
  
      
### Use a token to join a channel

The client requests a token from your authentication server corresponding to the user ID and the channel name. You use the received token to join a channel.

```swift
// Channel name
let channelId: String = "xxxx"
// User ID
let uid: UInt = 0
// Request the server to generate a token corresponding to channelId and uid
let token = getToken()
// Set channel media options
let mediaOption = AgoraRtcChannelMediaOptions()
// Set the user role as host
mediaOption.clientRoleType = .broadcaster
// Use the token to join a channel
agoraKit.joinChannel(byToken: token, channelId: channelId, uid: uid, mediaOptions: mediaOption)
```

### Token expiration

After you join a channel using a token, the SDK triggers an `onTokenPrivilegeWillExpire` callback, 30 seconds before the token is set to expire.

When the token expires, the SDK triggers an `onRequestToken` callback. After receiving the callback, you regenerate a new token on the server side, and then update the token in one of the following ways:

#### Single channel use-case

* Call `renewToken` to pass in the newly generated Token (Recommended).

* Call `updateChannelWithMediaOptions` to update the token.

* Call `leaveChannel` \[2/2] to leave the current channel, and then pass in a new token when calling `joinChannelByToken` \[2/4] to rejoin the channel.

#### Multi-channel use-case

If you call `joinChannelEx` to join multiple channels, call the `updateChannelExWithMediaOptions` method to update the token.

The following sample code demonstrates how to call `renewToken` to update the token upon receiving an `tokenPrivilegeWillExpire` callback notification.

```swift
extension JoinChannelVideoToken: AgoraRtcEngineDelegate {
    // Callback is triggered when the token is about to expire
    func rtcEngine(_ engine: AgoraRtcEngineKit, tokenPrivilegeWillExpire token: String) {
        // Request to generate a fresh token
        let token = getToken()
        // Update token
        engine.renewToken(token)
    }
}
```

### Complete sample code

For a complete implementation of token authentication, replace the content in `ViewController.swift` with the following code. Replace `Your App ID` with your App ID and `<Your Host URL and port>` with the host URL and port of the local Golang server you have deployed. For example, 123.1.23.123:8082.

**Complete sample code for token authentication**

```swift
    import UIKit
    import AgoraRtcKit
    import Foundation

    public enum TokenError: Error{
        case noData
        case invalidData
    }

    class ViewController: UIViewController {
        var localView: UIView!
        var remoteView: UIView!

        var agoraKit: AgoraRtcEngineKit!

        override func viewDidLoad() {
            super.viewDidLoad()
            //After loading the view, you can make other settings
            initView()
            initializeAgoraEngine()
            setClientRole()
            setupLocalVideo()
            fetchToken(channelName: "test", userId: 1234, role: 1){ result in
                switch result {
                case .success(let token):
                    print("token is: \(token)")
                    self.joinChannel(token: token)
                case .failure(let err):
                    print("Could not fetch token: \(err)")
                }
            }
        }

        override func viewDidLayoutSubviews(){
            super.viewDidLayoutSubviews()
            remoteView.frame = self.view.bounds
            localView.frame = CGRect(x: self.view.bounds.width - 90, y: 0, width: 90, height: 160)
        }

        override func viewDidDisappear(_ animated: Bool) {
            super.viewDidDisappear(true)
            leaveChannel()
            destroy()
        }

        func initView(){
            remoteView = UIView()
            self.view.addSubview(remoteView)
            localView = UIView()
            self.view.addSubview(localView)
        }

        func initializeAgoraEngine(){
            let config = AgoraRtcEngineConfig()
            config.appId = "Your App ID"
            config.channelProfile = .liveBroadcasting
            agoraKit = AgoraRtcEngineKit.sharedEngine(with: config, delegate: self)
            if agoraKit != nil{
                print("Initialization successful")
            }
            else{
                print("Initialization failed")
            }
        }

        func setClientRole(){
            agoraKit.setClientRole(.broadcaster)
        }

        func setupLocalVideo(){
            agoraKit.enableVideo()
            agoraKit.startPreview()
            let videoCanvas = AgoraRtcVideoCanvas()
            videoCanvas.uid = 0
            videoCanvas.renderMode = .hidden
            videoCanvas.view = localView
            agoraKit.setupLocalVideo(videoCanvas)
        }

        func joinChannel(token:String){
            let option = AgoraRtcChannelMediaOptions()
            agoraKit.joinChannel(byToken: token, channelId: "test", uid: 123456, mediaOptions: option)
        }

        func leaveChannel(){
            agoraKit.stopPreview()
            agoraKit.leaveChannel(nil)
        }

        func destroy(){
            AgoraRtcEngineKit.destroy()
        }

        func fetchToken(channelName: String, userId: UInt, role: UInt,
            callback: @escaping (Result<String, Error>) -> Void
        ){
            let url = URL(string: "http://<Your Host URL and port>/fetch_rtc_token")
            let parameters = ["uid":userId,"channelName": channelName, "role": role] as [String : Any]

            print(parameters.self)

            var request = URLRequest(
                url: url!,
                timeoutInterval: 10
            )

            request.httpMethod = "POST"

            do {
                request.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
            }
            catch let error {
                print(error.localizedDescription)
            }

            URLSession.shared.dataTask(with: request){data, _, err in
                guard let data = data else {
                    if let err = err {
                        callback(.failure(err))
                    }
                    else {
                        callback(.failure(TokenError.noData))
                    }
                return
            }

            let responseJSON = try? JSONSerialization.jsonObject(with: data, options: [])

            if let responseDict = responseJSON as? [String: Any], let token = responseDict["token"] as? String {
                callback(.success(token))
            } else {
                callback(.failure(TokenError.invalidData))
            }

        }.resume()
    }
    }

    extension ViewController: AgoraRtcEngineDelegate{
        func rtcEngine(_ engine: AgoraRtcEngineKit, didJoinedOfUid uid: UInt, elapsed: Int){
            let videoCanvas = AgoraRtcVideoCanvas()
            videoCanvas.uid = uid
            videoCanvas.renderMode = .hidden
            videoCanvas.view = remoteView
            agoraKit.setupRemoteVideo(videoCanvas)
        }

        func rtcEngine(_ engine: AgoraRtcEngineKit, tokenPrivilegeWillExpire token: String) {
            self.fetchToken(channelName: "test", userId: 1234, role: 1){ result in
                switch result {
                case .success(let token):
                    print("token is: \(token)")
                    self.agoraKit.renewToken(token)
                    print("Renewed the token")
                case .failure(let err):
                    print("Could not fetch token: \(err)")
                }
            }
        }

        func rtcEngine(_ engine: AgoraRtcEngineKit, connectionStateChanged state: AgoraConnectionState, reason: AgoraConnectionChangedReason) {
            print("Connection state changed to")
            print(state.rawValue)
        }

        func rtcEngineRequestToken(_ engine: AgoraRtcEngineKit) {
            fetchToken(channelName: "test", userId: 1234, role: 1){ result in
                switch result {
                    case .success(let token):
                        print("token is: \(token)")
                        self.joinChannel(token: token)
                    case .failure(let err):
                        print("Could not fetch token: \(err)")
                    }
            }
        }
    }
```

    
  
      
  
      
  
      
  
      
  
      
  
      
  
      
  
      
  
<CalloutContainer type="warning">
  <CalloutTitle>
    Note
  </CalloutTitle>

  <CalloutDescription>
    The user ID and channel name used to join a channel must be consistent with the values used to generate the token.
  </CalloutDescription>
</CalloutContainer>

## Reference

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

      
  
      
  
      
### API reference

* [`joinChannel`](https://api-ref.agora.io/en/video-sdk/ios/4.x/documentation/agorartckit/agorartcenginekit/joinchannel%28bytoken\:channelid\:info\:uid\:joinsuccess:%29)

* [`renewToken`](https://api-ref.agora.io/en/video-sdk/ios/4.x/documentation/agorartckit/agorartcenginekit/renewtoken%28_:%29)

* [`rtcEngine(_:tokenPrivilegeWillExpire:)`](https://api-ref.agora.io/en/video-sdk/ios/4.x/documentation/agorartckit/agorartcenginedelegate/rtcengine%28_\:tokenprivilegewillexpire:%29)