Telnyx Flutter Voice SDK

Enable Telnyx real-time communication services on Flutter applications (Android / iOS / Web) :telephone_receiver: :fire:

Quick Start with Telnyx Common (Beta)

Looking for a faster implementation? Check out Telnyx Common - available on pub.dev. Telnyx Common is a comprehensive Flutter package that abstracts away the complexity of implementing WebRTC voice calling functionality. It sits on top of the lower-level telnyx_webrtc package and provides a unified, easy-to-use API for developers who want to integrate voice calling capabilities into their Flutter applications without dealing with the intricate details of WebRTC, push notifications, and platform-specific implementations. This is the quickest way to implement the SDK with minimal setup and configuration.

Note: Telnyx Common is currently in beta. While it significantly simplifies implementation, you may encounter some limitations or changes as the library evolves.

Features
Usage
- SIP Credentials
- Platform Specific Configuration
  - Android
  - iOS
Basic Usage
Call Quality Metrics
Advanced Usage - Push Notifications
AI Agent Usage
Additional Resources
License

Features

Usage

SIP Credentials

In order to start making and receiving calls using the TelnyxRTC SDK you will need to get SIP Credentials: Screenshot 2022-07-15 at 13 51 45

Access to https://portal.telnyx.com/
Sign up for a Telnyx Account.
Create a Credential Connection to configure how you connect your calls.
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.

Platform Specific Configuration

Android

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" />

iOS

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>

Basic Usage

Telnyx Client

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();

Logging Configuration

The SDK provides a flexible logging system that allows you to control the verbosity of logs and even implement your own custom logging solution. There are two main aspects to configure:

Log Level The LogLevel enum determines which types of logs are displayed:

enum LogLevel {
  none,    // Disable all logs (default)
  error,   // Print error logs only
  warning, // Print warning logs only
  debug,   // Print debug logs only
  info,    // Print info logs only
  verto,   // Print verto protocol messages
  all      // Print all logs
}

Custom Logger You can implement your own logging solution by extending the CustomLogger abstract class:

class MyCustomLogger extends CustomLogger {
  @override
  log(LogLevel level, String message) {
    print('[$level] $message');
    // Implement any extra logging logic you would like here (eg. Send to a server, write to a file, etc.)
  }
}

Both the log level and custom logger can be configured in the Config class:

var config = CredentialConfig(
  sipUser: 'username',
  sipPassword: 'password',
  sipCallerIDName: 'Caller Name',
  sipCallerIDNumber: '1234567890',
  debug: true,  // Enable debug mode which allows you to track call metrics and download them from the portal - this is different to the log level and custom logger
  logLevel: LogLevel.debug,  // Set log level
  customLogger: MyCustomLogger(),  // Optional: provide custom logger
);

Logging into Telnyx Client

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;
}

Creating a call invitation

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");

Accepting a call

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:
            // This will return an instance of the Call class which can be used to interact with the call or monitor it's state.
            _incomingInvite = message.message.inviteParams;
            _call = _telnyxClient.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;
      }
    }
};

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.

Decline / End Call

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);
    }

DTMF (Dual Tone Multi Frequency)

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);

Mute a call

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

    _telnyxClient.call.onMuteUnmutePressed();

Toggle loud speaker

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

    _telnyxClient.call.enableSpeakerPhone(true);

Put a call on hold

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

    _telnyxClient.call.onHoldUnholdPressed();

Call Quality Metrics

The SDK provides real-time call quality metrics through the onCallQualityChange callback on the Call object. This allows you to monitor call quality in real-time and provide feedback to users.

Enabling Call Quality Metrics

To enable call quality metrics, set the debug parameter to true when creating or answering a call:

// When making a call
call.newInvite(
    callerName: "John Doe",
    callerNumber: "+1234567890",
    destinationNumber: "+1987654321",
    clientState: "some-state",
    debug: true
);

// When answering a call
call.acceptCall(
    callId: callId,
    destinationNumber: "destination",
    debug: true
);

// Listen for call quality metrics
call.onCallQualityChange = (metrics) {
    // Access metrics.jitter, metrics.rtt, metrics.mos, metrics.quality
    print("Call quality: ${metrics.quality}");
    print("MOS score: ${metrics.mos}");
    print("Jitter: ${metrics.jitter * 1000} ms");
    print("Round-trip time: ${metrics.rtt * 1000} ms");
};

CallQualityMetrics Properties

The CallQualityMetrics object provides the following properties:

Property	Type	Description
`jitter`	double	Jitter in seconds (multiply by 1000 for milliseconds)
`rtt`	double	Round-trip time in seconds (multiply by 1000 for milliseconds)
`mos`	double	Mean Opinion Score (1.0-5.0)
`quality`	CallQuality	Call quality rating based on MOS
`inboundAudio`	`Map<String, dynamic>?`	Inbound audio statistics
`outboundAudio`	`Map<String, dynamic>?`	Outbound audio statistics

CallQuality Enum

The CallQuality enum provides the following values:

Value	MOS Range	Description
`excellent`	`MOS > 4.2`	Excellent call quality
`good`	`4.1 <= MOS <= 4.2`	Good call quality
`fair`	`3.7 <= MOS <= 4.0`	Fair call quality
`poor`	`3.1 <= MOS <= 3.6`	Poor call quality
`bad`	`MOS <= 3.0`	Bad call quality
`unknown`	N/A	Unable to calculate quality

Advanced Usage - Push Notifications

Adding push notifications - Android platform

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. Note: for flutter, an easy way to add the firebase configuration after setting up the firebase project is to simply run the flutterfire configure command in the terminal. For example, if your firebase project is called myproject you would run flutterfire configure myproject. This will generate all the required files and configurations for your project. 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:

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());
}

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);
    }

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 SDK now handles this automatically.
        * Simply set the decline flag and the SDK will handle the rest using the new push_decline method.
        * */
         TelnyxClient.setPushMetaData(
                 message.data, isAnswer: false, isDecline: true);
          break;
       }});
}

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);
      }
    }

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;
   });

Best Practices for Push Notifications on Android

Request for Notification Permissions for android 13+ devices to show push notifications. More information can be found here
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).
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;
      });

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);

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
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;
            }

          }
        ...
      }
 }

Adding push notifications - iOS platform

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

        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("")
        }

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)
         
         }                         

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)
            }
        }

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;
   });

Handling Late Notifications

If notifications 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;
}

Best Practices for Push Notifications on iOS

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.

New Push Notification Features

Simplified Push Decline Method

The SDK now includes a simplified method for declining push notifications. Previously, you needed to log back into the socket, listen for events, wait for an invite, and manually send a bye message. New Approach: The SDK automatically handles call decline when you set the decline flag in setPushMetaData. The SDK will:

Connect to the socket
Send a login message with decline_push: true parameter
Automatically handle ending the call
Disconnect from the socket

// When declining a push notification, simply set the decline flag
TelnyxClient.setPushMetaData(message.data, isAnswer: false, isDecline: true);

// Then call handlePushNotification as usual
_telnyxClient.handlePushNotification(pushMetaData, credentialConfig, tokenConfig);

10-Second Answer Timeout

The SDK now includes an automatic timeout mechanism for push notifications. When you accept a push notification but no INVITE message arrives on the socket within 10 seconds, the SDK will:

Automatically consider the call cancelled
Emit a bye message internally with ORIGINATOR_CANCEL termination reason (SIP code 487)
Prevent indefinite waiting for missing INVITE messages

This timeout mechanism activates automatically when:

A push notification is accepted (isAnswer: true)
The SDK connects and waits for an INVITE message
No INVITE is received within 10 seconds

Normal Flow: User accepts push → Timer starts → INVITE received → Timer cancelled → Call proceeds Timeout Flow: User accepts push → Timer starts → No INVITE received → Timer expires → Call terminated with ORIGINATOR_CANCEL No additional code is required to use this feature - it’s handled automatically by the SDK.

AI Agent Usage

The Flutter Voice SDK supports Voice AI Agent implementations. To get started, follow the steps described here to build your first AI Assistant. Once your AI Agent is up and running, you can use the SDK to communicate with your AI Agent with the following steps:

1. Logging in to communicate with the AI Agent.

To connect with an AI Assistant, you can use the anonymousLogin method. This allows you to establish a connection without traditional authentication credentials. This method takes a targetId which is the ID of your AI assistant, and an optional targetVersionId. If a targetVersionId is not provided, the SDK will use the latest version available. Note: After a successful anonymousLogin, any subsequent call, regardless of the destination, will be directed to the specified AI Assistant. Here’s an example of how to use it:

try {
  await _telnyxClient.anonymousLogin(
    targetId: 'your_assistant_id',
    // targetType: 'ai_assistant', // This is the default value
    // targetVersionId: 'your_assistant_version_id' // Optional
  );
  // You are now connected and can make a call to the AI Assistant.
} catch (e) {
  // Handle login error
}

Once connected, you can use the standard newInvite method to start a conversation with the AI Assistant.

2. Starting a Conversation with the AI Assistant

After a successful anonymousLogin, you can initiate a call to your AI Assistant using the newInvite method. Because the session is now locked to the AI Assistant, the destinationNumber parameter in the newInvite method will be ignored. Any values provided for callerName and callerNumber will be passed on, but the call will always be routed to the AI Assistant specified during the login. Here is an example of how to start the call:

// After a successful anonymousLogin...

_telnyxClient.newInvite(
  'Your Name',
  'Your Number',
  '', // Destination is ignored, can be an empty string
  'Your custom state'
);

The call will be automatically answered by the AI Assistant. From this point on, the call flow is handled in the same way as any other answered call, allowing you to use standard call control methods like endCall, mute, etc.

3. Receiving Transcript Updates

During an AI Assistant conversation, the SDK provides real-time transcript updates that include both the caller’s speech and the AI Assistant’s responses. This allows you to display a live conversation transcript in your application. To receive transcript updates, set up the onTranscriptUpdate callback on your TelnyxClient instance:

_telnyxClient.onTranscriptUpdate = (List<TranscriptItem> transcript) {
  // Handle the updated transcript
  for (var item in transcript) {
    print('${item.role}: ${item.content}');
    // item.role will be either 'user' or 'assistant'
    // item.content contains the spoken text
    // item.timestamp contains when the message was received
  }
  
  // Update your UI to display the conversation
  setState(() {
    _conversationTranscript = transcript;
  });
};

The TranscriptItem contains the following properties:

id: Unique identifier for the transcript item
role: Either ‘user’ (for the caller) or ‘assistant’ (for the AI Agent)
content: The transcribed text content
timestamp: When the transcript item was created

You can also manually retrieve the current transcript at any time:

List<TranscriptItem> currentTranscript = _telnyxClient.transcript;

To clear the transcript (for example, when starting a new conversation):

_telnyxClient.clearTranscript();

Note: Transcript updates are only available during AI Assistant conversations initiated through anonymousLogin. Regular calls between users do not provide transcript functionality.

4. Sending a text message to the AI Agent

In addition to voice conversation, you can send text messages directly to the AI Agent during an active call. This allows for mixed-mode communication where users can both speak and type messages to the AI Assistant. To send a text message to the AI Agent, use the sendConversationMessage method on the active call instance:

// Get the active call instance (after successfully connecting and calling)
Call? activeCall = _telnyxClient.calls.values.firstOrNull;

if (activeCall != null) {
  // Send a text message to the AI Agent
  activeCall.sendConversationMessage("Hello, can you help me with my account?");
}

You can also retrieve the call by its ID if you have it:

// If you have the call ID
String callId = "your-call-id";
Call? call = _telnyxClient.getCallOrNull(callId);

if (call != null) {
  call.sendConversationMessage("I need assistance with billing.");
}

Important Notes:

The sendConversationMessage method is only available during AI Assistant conversations
Text messages sent this way will appear in the transcript updates alongside spoken conversation
The AI Agent will process and respond to text messages just like spoken input
You must have an active call established before sending text messages

This feature enables rich conversational experiences where users can seamlessly switch between voice and text communication with the AI Assistant.

Additional Resources

Official SDK Documentation

Questions? Comments? Building something rad? Join our Slack channel and share.

APIs fundamentals

Server-side SDKs

WebRTC SDKs

Development Tools

For AI Agents

Migration Guides

​Telnyx Flutter Voice SDK

​Quick Start with Telnyx Common (Beta)

​Table of Contents

​Features

​Usage

​SIP Credentials

​Platform Specific Configuration

​Android

​iOS

​Basic Usage

​Telnyx Client

​Logging Configuration

​Logging into Telnyx Client

​Creating a call invitation

​Accepting a call

​Decline / End Call

​DTMF (Dual Tone Multi Frequency)

​Mute a call

​Toggle loud speaker

​Put a call on hold

​Call Quality Metrics

​Enabling Call Quality Metrics

​CallQualityMetrics Properties

​CallQuality Enum

​Advanced Usage - Push Notifications

​Adding push notifications - Android platform

​Best Practices for Push Notifications on Android

​Adding push notifications - iOS platform

​Handling Late Notifications

​Best Practices for Push Notifications on iOS

​New Push Notification Features

​Simplified Push Decline Method

​10-Second Answer Timeout

​AI Agent Usage

​1. Logging in to communicate with the AI Agent.

​2. Starting a Conversation with the AI Assistant

​3. Receiving Transcript Updates

​4. Sending a text message to the AI Agent

​Additional Resources

​License