Telnyx Flutter Voice SDK

Enable Telnyx real-time communication services on Flutter applications (Android / iOS / Web) 📞 🔥

• Create / Receive calls
• Hold calls
• Mute calls
• Dual Tone Multi Frequency

In order to start making and receiving calls using the TelnyxRTC SDK you will need to get SIP Credentials:

1. Access to https://portal.telnyx.com/
2. Sign up for a Telnyx Account.
3. Create a Credential Connection to configure how you connect your calls.
4. Create an Outbound Voice Profile to configure your outbound call settings and assign it to your Credential Connection.

For more information on how to generate SIP credentials check the Telnyx WebRTC quickstart guide.

If you are implementing the SDK into an Android application it is important to remember to add the following permissions to your AndroidManifest in order to allow Audio and Internet permissions:

    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
    <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />

on the iOS platform, you need to add the microphone permission to your Info.plist file:

    <key>NSMicrophoneUsageDescription</key>
    <string>$(PRODUCT_NAME) Microphone Usage!</string>

TelnyxClient() is the core class of the SDK, and can be used to connect to our backend socket connection, create calls, check state and disconnect, etc.

Once an instance is created, you can call the .connect() method to connect to the socket with either a token or credentials (see below). An error will appear as a socket response if there is no network available:

    TelnyxClient _telnyxClient = TelnyxClient();

To log into the Telnyx WebRTC client, you'll need to authenticate using a Telnyx SIP Connection. Follow our quickstart guide to create JWTs (JSON Web Tokens) to authenticate. To log in with a token we use the connectWithToken() method. You can also authenticate directly with the SIP Connection username and password with the connectWithCredential() method:

   _telnyxClient.connectWithToken(tokenConfig)
                    //OR
   _telnyxClient.connectWithCredential(credentialConfig)             

Note: tokenConfig and credentialConfig are simple classes that represent login settings for the client to use they extend a base Config class with shared properties. They look like this:

/// Creates an instance of CredentialConfig which can be used to log in
///
/// Uses the [sipUser] and [sipPassword] fields to log in
/// [sipCallerIDName] and [sipCallerIDNumber] will be the Name and Number associated
/// [notificationToken] is the token used to register the device for notifications if required (FCM or APNS)
/// The [autoReconnect] flag decided whether or not to attempt a reconnect (3 attempts) in the case of a login failure with
/// legitimate credentials
class CredentialConfig extends Config {
  CredentialConfig({
     required this.sipUser,
     required this.sipPassword,
     required super.sipCallerIDName,
     required super.sipCallerIDNumber,
     super.notificationToken,
     super.autoReconnect,
     required super.debug,
     super.ringTonePath,
     super.ringbackPath,
  });

  final String sipUser;
  final String sipPassword;
}

/// Creates an instance of TokenConfig which can be used to log in
///
/// Uses the [sipToken] field to log in
/// [sipCallerIDName] and [sipCallerIDNumber] will be the Name and Number associated
/// [notificationToken] is the token used to register the device for notifications if required (FCM or APNS)
/// The [autoReconnect] flag decided whether or not to attempt a reconnect (3 attempts) in the case of a login failure with
/// a legitimate token
class TokenConfig extends Config {
  TokenConfig({
     required this.sipToken,
     required super.sipCallerIDName,
     required super.sipCallerIDNumber,
     super.notificationToken,
     super.autoReconnect,
     required super.debug,
     super.ringTonePath,
     super.ringbackPath,
  });

  final String sipToken;
}

The Android platform makes use of Firebase Cloud Messaging in order to deliver push notifications. To receive notifications when receiving calls on your Android mobile device you will have to enable Firebase Cloud Messaging within your application. For a detailed tutorial, please visit our official Push Notification Docs. The Demo app uses the FlutterCallkitIncoming plugin to show incoming calls. To show a notification when receiving a call, you can follow the steps below:

1. Listen for Background Push Notifications, Implement the FirebaseMessaging.onBackgroundMessage method in your main method

@pragma('vm:entry-point')
Future<void> main() async {
    WidgetsFlutterBinding.ensureInitialized();

    if (defaultTargetPlatform == TargetPlatform.android) {
      // Android Only - Push Notifications
        await Firebase.initializeApp();
        FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);
      
        await FirebaseMessaging.instance
                .setForegroundNotificationPresentationOptions(
         alert: true,
         badge: true,
         sound: true,
      );
    }
      runApp(const MyApp());
}

2. Optionally Add the metadata to CallKitParams extra field

    static Future showNotification(RemoteMessage message)  {
      CallKitParams callKitParams = CallKitParams(
        android:...,
          ios:...,
          extra: message.data,
      )
      await FlutterCallkitIncoming.showCallkitIncoming(callKitParams);
    }

3. Handle the push notification in the _firebaseMessagingBackgroundHandler method

Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
      //show notifcation
      showNotification(message);
      
      //Listen to action from FlutterCallkitIncoming
      FlutterCallkitIncoming.onEvent.listen((CallEvent? event) async {
       switch (event!.event) {
        case Event.actionCallAccept:
         // Set the telnyx metadata for access when the app comes to foreground
         TelnyxClient.setPushMetaData(
                 message.data, isAnswer: true, isDecline: false);
         break;
        case Event.actionCallDecline:
        /*
        * When the user declines the call from the push notification, the app will no longer be visible, and we have to
        * handle the endCall user here.
        * Login to the TelnyxClient and end the call
        * */
          ...
       }});
}

4. Use the TelnyxClient.getPushMetaData() method to retrieve the metadata when the app comes to the foreground. This data is only available on 1st access and becomes null afterward.

    Future<void> _handlePushNotification() async {
       final  data = await TelnyxClient.getPushMetaData();
       PushMetaData? pushMetaData = PushMetaData.fromJson(data);
      if (pushMetaData != null) {
        _telnyxClient.handlePushNotification(pushMetaData, credentialConfig, tokenConfig);
      }
    }

5. To Handle push calls on foreground, Listen for Call Events and invoke the handlePushNotification method

FlutterCallkitIncoming.onEvent.listen((CallEvent? event) {
   switch (event!.event) {
   case Event.actionCallIncoming:
   // retrieve the push metadata from extras
   final data = await TelnyxClient.getPushData();
   ...
  _telnyxClient.handlePushNotification(pushMetaData, credentialConfig, tokenConfig);
    break;
   case Event.actionCallStart:
    ....
   break;
   case Event.actionCallAccept:
     ...
   logger.i('Call Accepted Attach Call');
   break;
   });

1. Request for Notification Permissions for android 13+ devices to show push notifications. More information can be found here
2. Push Notifications only work in foreground for apps that are run in debug mode (You will not receive push notifications when you terminate the app while running in debug mode).
3. On Foreground calls, you can use the FirebaseMessaging.onMessage.listen method to listen for incoming calls and show a notification.

 FirebaseMessaging.onMessage.listen((RemoteMessage message) {
        TelnyxClient.setPushMetaData(message.data);
        NotificationService.showNotification(message);
        mainViewModel.callFromPush = true;
      });

4. To handle push notifications on the background, use the FirebaseMessaging.onBackgroundMessage method to listen for incoming calls and show a notification and make sure to set the TelnyxClient.setPushMetaData when user answers the call.

 TelnyxClient.setPushMetaData(
                 message.data, isAnswer: true, isDecline: false);

5. When you call the telnyxClient.handlePushNotification it connects to the telnyxClient, make sure not to call the telnyxClient.connect() method after this. e.g an Edge case might be if you call telnyxClient.connect() on Widget init method it will always call the connect method

6. Early Answer/Decline : Users may answer/decline the call too early before a socket connection is established. To handle this situation, assert if the IncomingInviteParams is not null and only accept/decline if this is availalble.

bool waitingForInvite = false;

void accept() {

if (_incomingInvite != null) {
  // accept the call if the incomingInvite arrives on time 
      _currentCall = _telnyxClient.acceptCall(
          _incomingInvite!, _localName, _localNumber, "State");
    } else {
      // set waitingForInvite to true if we have an early accept
      waitingForInvite = true;
    }
}


 _telnyxClient.onSocketMessageReceived = (TelnyxMessage message) {
      switch (message.socketMethod) {
        ...
        case SocketMethod.INVITE:
          {
            if (callFromPush) {
              // For early accept of call
              if (waitingForInvite) {
                //accept the call
                accept();
                waitingForInvite = false;
              }
              callFromPush = false;
            }

          }
        ...
      }
 }

The iOS Platform makes use of the Apple Push Notification Service (APNS) and Pushkit in order to deliver and receive push notifications For a detailed tutorial, please visit our official Push Notification Docs

1. Register/Invalidate the push device token for iOS

        func pushRegistry(_ registry: PKPushRegistry, didUpdate credentials: PKPushCredentials, for type: PKPushType) {
            print(credentials.token)
            let deviceToken = credentials.token.map { String(format: "%02x", $0) }.joined()
            //Save deviceToken to your server
            SwiftFlutterCallkitIncomingPlugin.sharedInstance?.setDevicePushTokenVoIP(deviceToken)
        }
        
        func pushRegistry(_ registry: PKPushRegistry, didInvalidatePushTokenFor type: PKPushType) {
            SwiftFlutterCallkitIncomingPlugin.sharedInstance?.setDevicePushTokenVoIP("")
        }

2. For foreground calls to work, you need to register with callkit on the restorationHandler delegate function. You can also choose to register with callkit using iOS official documentation on CallKit.

  override func application(_ application: UIApplication,
                                  continue userActivity: NSUserActivity,
                                  restorationHandler: @escaping ([UIUserActivityRestoring]?) -> Void) -> Bool {
                                  
            let nameCaller = handleObj.getDecryptHandle()["nameCaller"] as? String ?? ""
            let handle = handleObj.getDecryptHandle()["handle"] as? String ?? ""
            let data = flutter_callkit_incoming.Data(id: UUID().uuidString, nameCaller: nameCaller, handle: handle, type: isVideo ? 1 : 0)
            //set more data...
            data.nameCaller = "dummy"
            SwiftFlutterCallkitIncomingPlugin.sharedInstance?.startCall(data, fromPushKit: true)
         
         }                         

3. Listen for incoming calls in AppDelegate.swift class

    func pushRegistry(_ registry: PKPushRegistry, didReceiveIncomingPushWith payload: PKPushPayload, for type: PKPushType, completion: @escaping () -> Void) {
            print("didReceiveIncomingPushWith")
            guard type == .voIP else { return }
            
            if let metadata = payload.dictionaryPayload["metadata"] as? [String: Any] {
                var callID = UUID.init().uuidString
                if let newCallId = (metadata["call_id"] as? String),
                   !newCallId.isEmpty {
                    callID = newCallId
                }
                let callerName = (metadata["caller_name"] as? String) ?? ""
                let callerNumber = (metadata["caller_number"] as? String) ?? ""
                
                let id = payload.dictionaryPayload["call_id"] as? String ??  UUID().uuidString
                
                let data = flutter_callkit_incoming.Data(id: id, nameCaller: callerName, handle: callerNumber, type: isVideo ? 1 : 0)
                data.extra = payload.dictionaryPayload as NSDictionary
                data.normalHandle = 1              
                
                let caller = callerName.isEmpty ? (callerNumber.isEmpty ? "Unknown" : callerNumber) : callerName
                let uuid = UUID(uuidString: callID)
                
                data.uuid = uuid!.uuidString
                data.nameCaller = caller
                
                SwiftFlutterCallkitIncomingPlugin.sharedInstance?.showCallkitIncoming(data, fromPushKit: true)
            }
        }

4. Listen for Call Events and invoke the handlePushNotification method

   FlutterCallkitIncoming.onEvent.listen((CallEvent? event) {
   switch (event!.event) {
   case Event.actionCallIncoming:
   // retrieve the push metadata from extras
    PushMetaData? pushMetaData = PushMetaData.fromJson(event.body['extra']['metadata']);
    _telnyxClient.handlePushNotification(pushMetaData, credentialConfig, tokenConfig);
    break;
   case Event.actionCallStart:
    ....
   break;
   case Event.actionCallAccept:
     ...
   logger.i('Call Accepted Attach Call');
   break;
   });

1. Push Notifications only work in foreground for apps that are run in debug mode (You will not receive push notifications when you terminate the app while running in debug mode). Make sure you are in release mode. Preferably test using Testfight or Appstore. To test if push notifications are working, disconnect the telnyx client (while app is in foreground) and make a call to the device. You should receive a push notification.

In order to make a call invitation, we first create an instance of the Call class with the .call instance. This creates a Call class which can be used to interact with calls (invite, accept, decline, etc). To then send an invite, we can use the .newInvite() method which requires you to provide your callerName, callerNumber, the destinationNumber (or SIP credential), and your clientState (any String value).

    _telnyxClient
        .call
        .newInvite("callerName", "000000000", destination, "State");

In order to be able to accept a call, we first need to listen for invitations. We do this by getting the Telnyx Socket Response callbacks:

 // Observe Socket Messages Received
_telnyxClient.onSocketMessageReceived = (TelnyxMessage message) {
  switch (message.socketMethod) {
        case SocketMethod.CLIENT_READY:
        {
           // Fires once client has correctly been setup and logged into, you can now make calls. 
           break;
        }
        case SocketMethod.LOGIN:
        {
            // Handle a successful login - Update UI or Navigate to new screen, etc. 
            break;
        }
        case SocketMethod.INVITE:
        {
            // Handle an invitation Update UI or Navigate to new screen, etc. 
            // Then, through an answer button of some kind we can accept the call with:
            _incomingInvite = message.message.inviteParams;
            _telnyxClient.createCall().acceptCall(
                _incomingInvite, "callerName", "000000000", "State");
            break;
        }
        case SocketMethod.ANSWER:
        {
           // Handle a received call answer - Update UI or Navigate to new screen, etc.
          break;
        }
        case SocketMethod.BYE:
        {
           // Handle a call rejection or ending - Update UI or Navigate to new screen, etc.
           break;
      }
    }
    notifyListeners();
};

We can then use this method to create a listener that listens for an invitation and, in this case, answers it straight away. A real implementation would be more suited to show some UI and allow manual accept / decline operations.

In order to end a call, we can get a stored instance of Call and call the .endCall(callID) method. To decline an incoming call we first create the call with the .createCall() method and then call the .endCall(callID) method:

    if (_ongoingCall) {
      _telnyxClient.call.endCall(_telnyxClient.call.callId);
    } else {
      _telnyxClient.createCall().endCall(_incomingInvite?.callID);
    }

If notifcations arrive very late due to no internet connectivity, It is good to always flag it as a missed call. You can do that using the code snippet below :

const CALL_MISSED_TIMEOUT = 60;

 DateTime nowTime = DateTime.now();
 Duration? difference = nowTime?.difference(message.sentTime!);

 if (difference.inSeconds > CALL_MISSED_TIMEOUT) {
    NotificationService.showMissedCallNotification(message);
    return;
}

In order to send a DTMF message while on a call you can call the .dtmf(callID, tone), method where tone is a String value of the character you would like pressed:

    _telnyxClient.call.dtmf(_telnyxClient.call.callId, tone);

To mute a call, you can simply call the .onMuteUnmutePressed() method:

    _telnyxClient.call.onMuteUnmutePressed();

To toggle loud speaker, you can simply call .enableSpeakerPhone(bool):

    _telnyxClient.call.enableSpeakerPhone(true);

To put a call on hold, you can simply call the .onHoldUnholdPressed() method:

    _telnyxClient.call.onHoldUnholdPressed();

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