Infer Twilio callback URL automatically

twilio-voice-app/.env.example

@@ -3,10 +3,6 @@ TWILIO_ACCOUNT_SID=ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 TWILIO_AUTH_TOKEN=your_auth_token
 TWILIO_PHONE_NUMBER=+1234567890
 
-# Publicly accessible URL (https://...) that Twilio can reach.
-# When running locally use a tunneling tool such as ngrok and paste the HTTPS URL.
-PUBLIC_SERVER_URL=https://your-ngrok-id.ngrok-free.app
-
 # Optional: choose a Pollinations voice for TTS playback
 POLLINATIONS_VOICE=nova
 

twilio-voice-app/README.md

@@ -29,7 +29,6 @@ A lightweight Node + Twilio companion service that lets Unity call a phone numbe
    ```
    Required variables:
    - `TWILIO_ACCOUNT_SID`, `TWILIO_AUTH_TOKEN`, `TWILIO_PHONE_NUMBER`
-   - `PUBLIC_SERVER_URL` – The **public** HTTPS URL that Twilio will call back (e.g. your ngrok tunnel).
    - Optional: `POLLINATIONS_VOICE` to choose a different Pollinations voice preset.
 3. Start the server:
    ```bash
@@ -40,10 +39,10 @@ A lightweight Node + Twilio companion service that lets Unity call a phone numbe
    # Example using ngrok (server must already be running on PORT)
    ngrok http 4000
    ```
-5. Update `PUBLIC_SERVER_URL` in your `.env` with the HTTPS forwarding address printed by ngrok and restart the server if needed.
-
 Visit [http://localhost:4000](http://localhost:4000) to load the dashboard, enter a phone number, and press **Call My Phone**. Answer the incoming call from your Twilio number to begin the voice chat.
 
+> ℹ️ The server automatically infers its public URL from the incoming browser request when you press **Call My Phone**. Ensure you access the dashboard through the same public HTTPS address (for example, the ngrok URL) so Twilio receives a reachable callback URL.
+
 ## Twilio configuration tips
 
 - Trial accounts can only call verified numbers. Add your mobile phone to the **Verified Caller IDs** page in the Twilio Console.

twilio-voice-app/server.js

@@ -12,7 +12,6 @@ if (!fetchImpl) {
 }
 
 const PORT = process.env.PORT || 4000;
-const PUBLIC_SERVER_URL = process.env.PUBLIC_SERVER_URL;
 const TWILIO_ACCOUNT_SID = process.env.TWILIO_ACCOUNT_SID;
 const TWILIO_AUTH_TOKEN = process.env.TWILIO_AUTH_TOKEN;
 const TWILIO_PHONE_NUMBER = process.env.TWILIO_PHONE_NUMBER;
@@ -24,11 +23,8 @@ const hasTwilioCredentials =
 if (!hasTwilioCredentials) {
   console.warn('[WARN] Twilio credentials are not fully configured. API routes will return errors.');
 }
-if (!PUBLIC_SERVER_URL) {
-  console.warn('[WARN] PUBLIC_SERVER_URL is not set. Twilio callbacks will fail without a public URL.');
-}
-
 const app = express();
+app.set('trust proxy', true);
 app.use(express.json());
 app.use(express.urlencoded({ extended: true }));
 
@@ -146,15 +142,15 @@ function buildVoiceResponse(session, twiml, promptMessage, gatherPrompt) {
   return twiml;
 }
 
-async function startPhoneCall(session) {
+async function startPhoneCall(session, baseUrl) {
   if (!client) {
     throw new Error('Twilio client is not configured.');
   }
-  if (!PUBLIC_SERVER_URL) {
-    throw new Error('PUBLIC_SERVER_URL is not configured.');
+  if (!baseUrl) {
+    throw new Error('Unable to determine a public server URL from the request.');
   }
 
-  const voiceUrl = new URL('/voice-response', PUBLIC_SERVER_URL);
+  const voiceUrl = new URL('/voice-response', baseUrl);
   voiceUrl.searchParams.set('sessionId', session.id);
 
   return client.calls.create({
@@ -165,6 +161,15 @@ async function startPhoneCall(session) {
   });
 }
 
+function resolvePublicBaseUrl(req) {
+  const forwardedProto = req.headers['x-forwarded-proto'];
+  const forwardedHost = req.headers['x-forwarded-host'];
+  const protocol = forwardedProto ? forwardedProto.split(',')[0] : req.protocol;
+  const host = forwardedHost ? forwardedHost.split(',')[0] : req.get('host');
+  if (!protocol || !host) return null;
+  return `${protocol}://${host}`;
+}
+
 app.post('/api/start-call', async (req, res) => {
   try {
     const { phoneNumber, initialPrompt, voice } = req.body || {};
@@ -174,8 +179,12 @@ app.post('/api/start-call', async (req, res) => {
     if (!client) {
       return res.status(500).json({ error: 'Twilio credentials are missing on the server.' });
     }
-    if (!PUBLIC_SERVER_URL) {
-      return res.status(500).json({ error: 'PUBLIC_SERVER_URL is not configured on the server.' });
+
+    const baseUrl = resolvePublicBaseUrl(req);
+    if (!baseUrl) {
+      return res.status(500).json({
+        error: 'Unable to infer the public URL from the request. Access the app via a public HTTPS address before starting a call.'
+      });
     }
 
     const session = createSession(phoneNumber.trim(), voice || DEFAULT_VOICE);
@@ -187,7 +196,7 @@ app.post('/api/start-call', async (req, res) => {
       await fetchPollinationsResponse(session, 'Greet the caller briefly and ask how you can help.');
     }
 
-    await startPhoneCall(session);
+    await startPhoneCall(session, baseUrl);
 
     res.json({
       sessionId: session.id,