Telnyx WebRTC – JavaScript SDK

Build real-time voice communication into browser applications.

Prerequisites: Create WebRTC credentials and generate a login token using the Telnyx server-side SDK. See the telnyx-webrtc-* skill in your server language plugin (e.g., telnyx-python, telnyx-javascript).

Installation

npm install @telnyx/webrtc --save

Import the client:

import { TelnyxRTC } from '@telnyx/webrtc';

Authentication

Option 1: Token-Based (Recommended)

const client = new TelnyxRTC({
  login_token: 'your_jwt_token',
});

client.connect();

Option 2: Credential-Based

const client = new TelnyxRTC({
  login: 'sip_username',
  password: 'sip_password',
});

client.connect();

Important: Never hardcode credentials in frontend code. Use environment variables or prompt users.

Disconnect

// When done, disconnect and remove listeners
client.disconnect();
client.off('telnyx.ready');
client.off('telnyx.notification');

Media Elements

Specify an HTML element to play remote audio:

client.remoteElement = 'remoteMedia';

HTML:

<audio id="remoteMedia" autoplay="true" />

Events

let activeCall;

client
  .on('telnyx.ready', () => {
    console.log('Ready to make calls');
  })
  .on('telnyx.error', (error) => {
    console.error('Error:', error);
  })
  .on('telnyx.notification', (notification) => {
    if (notification.type === 'callUpdate') {
      activeCall = notification.call;
      
      // Handle incoming call
      if (activeCall.state === 'ringing') {
        // Show incoming call UI
        // Call activeCall.answer() to accept
      }
    }
  });

Event Types

Making Calls

const call = client.newCall({
  destinationNumber: '+18004377950',
  callerNumber: '+15551234567',
});

Receiving Calls

client.on('telnyx.notification', (notification) => {
  const call = notification.call;
  
  if (notification.type === 'callUpdate' && call.state === 'ringing') {
    // Incoming call - show UI and answer
    call.answer();
  }
});

Call Controls

// End call
call.hangup();

// Send DTMF tones
call.dtmf('1234');

// Mute audio
call.muteAudio();
call.unmuteAudio();

// Hold
call.hold();
call.unhold();

Debugging & Call Quality

Enable Debug Logging

const call = client.newCall({
  destinationNumber: '+18004377950',
  debug: true,
  debugOutput: 'socket',  // 'socket' (send to Telnyx) or 'file' (save locally)
});

In-Call Quality Metrics

const call = client.newCall({
  destinationNumber: '+18004377950',
  debug: true,  // Required for metrics
});

client.on('telnyx.stats.frame', (stats) => {
  console.log('Quality stats:', stats);
  // Contains jitter, RTT, packet loss, etc.
});

Pre-Call Diagnosis

Test connectivity before making calls:

import { PreCallDiagnosis } from '@telnyx/webrtc';

PreCallDiagnosis.run({
  credentials: {
    login: 'sip_username',
    password: 'sip_password',
    // or: loginToken: 'jwt_token'
  },
  texMLApplicationNumber: '+12407758982',
})
  .then((report) => {
    console.log('Diagnosis report:', report);
  })
  .catch((error) => {
    console.error('Diagnosis failed:', error);
  });

Preferred Codecs

Set codec preference for calls:

const allCodecs = RTCRtpReceiver.getCapabilities('audio').codecs;

// Prefer Opus for AI/high quality
const opusCodec = allCodecs.find(c => 
  c.mimeType.toLowerCase().includes('opus')
);

// Or PCMA for telephony compatibility
const pcmaCodec = allCodecs.find(c => 
  c.mimeType.toLowerCase().includes('pcma')
);

client.newCall({
  destinationNumber: '+18004377950',
  preferred_codecs: [opusCodec],
});

Registration State

Check if client is registered:

const isRegistered = await client.getIsRegistered();
console.log('Registered:', isRegistered);

AI Agent Integration

Anonymous Login

Connect to an AI assistant without SIP credentials:

const client = new TelnyxRTC({
  anonymous_login: {
    target_id: 'your-ai-assistant-id',
    target_type: 'ai_assistant',
  },
});

client.connect();

Note: The AI assistant must have telephony_settings.supports_unauthenticated_web_calls set to true.

Make Call to AI Assistant

// After anonymous login, destinationNumber is ignored
const call = client.newCall({
  destinationNumber: '',  // Can be empty
  remoteElement: 'remoteMedia',
});

Recommended Codec for AI

const allCodecs = RTCRtpReceiver.getCapabilities('audio').codecs;
const opusCodec = allCodecs.find(c => 
  c.mimeType.toLowerCase().includes('opus')
);

client.newCall({
  destinationNumber: '',
  preferred_codecs: [opusCodec],  // Opus recommended for AI
});

Browser Support

Check Browser Support

const webRTCInfo = TelnyxRTC.webRTCInfo;
console.log('WebRTC supported:', webRTCInfo.supportWebRTC);

Troubleshooting

Resources

• Official Documentation
• npm Package
• GitHub Repository
• Demo App