To set up Audio Stream for Voice Bot please follow the below steps

Buy Phone Numbers from Plivo and Attach the Application:

Phone numbers can be bought from the “Phone numbers” Tab of Plivo Console

Create a new XML Application from Voice Tab. Add “Primary answer URL” and “Hangup URL”

Attach this XML application with the Phone number and Update the number

Use Ngrok to expose the local server to the internet:

Install ngrok and run

ngrok http 8080

The above steps can be achieved through APIs as well:

1. Search for Available Numbers (if you don't already know which one to buy): Replace {AUTH_ID} with your Plivo Auth ID, {AUTH_TOKEN} with your Plivo Auth Token

curl -i -X GET "https://api.plivo.com/v1/Account/{AUTH_ID}/PhoneNumber/?country_iso=US&type=local" \
-u {AUTH_ID}:{AUTH_TOKEN}

2. Create XML application: Replace {AUTH_ID} with your Plivo Auth ID, {AUTH_TOKEN} with your Plivo Auth Token and update “answer_url” and “hangup_url”

curl -i -X POST https://api.plivo.com/v1/Account/{AUTH_ID}/Application/ \
-u {AUTH_ID}:{AUTH_TOKEN} \
-H "Content-Type: application/json" \
-d '{ "app_name": "Voice-Bot", "answer_url": "https://4964-49-37-240-174.ngrok-free.app/answer_xml", "answer_method": "GET", "hangup_url": "https://4964-49-37-240-174.ngrok-free.app/hangup", "hangup_method": "POST" }'

Response:
{
  "api_id": "9d55ab63-ccf1-498e-89f3-6deb4b9a3c85",
  "app_id": "16525344707489756",
  "message": "created"
}

3. Buy a Phone Number: Replace {AUTH_ID} with your Plivo Auth ID, {AUTH_TOKEN} with your Plivo Auth Token, and {phone_number} with the number you want to purchase {APP_ID} from previous response

curl -i -X POST "https://api.plivo.com/v1/Account/{AUTH_ID}/PhoneNumber/{phone_number}/" \
-u {AUTH_ID}:{AUTH_TOKEN} \
-H "Content-Type: application/json" \
-d '{"app_id": "{APP_ID}"}'

Sample XML format for Plivo Audio stream:

The following XML creates a bidirectional audio stream and records the call: Store the XML file as stream.xml, which can be later used on the server.

<Response>
        <Record action="https://4964-49-37-240-174.ngrok-free.app/get_recording/" redirect="false" recordSession="true" maxLength="3600" />
        <Stream bidirectional="true" streamTimeout="120" contentType="audio/x-mulaw;rate=8000" keepCallAlive="true" statusCallbackUrl="https://4964-49-37-240-174.ngrok-free.app/ss">wss://5c53-2600-1f18-2653-ce05-21d3-2211-6985-5f50.ngrok-free.app/ws</Stream>
</Response>

Inbound Call:

Dial to the phone number purchased in the Plivo, It gets connected to the Audio stream, you will hear your audio back.

Outbound Call:

To Make the outbound call, Use the phone number purchased in the Plivo as the caller-ID or FROM number and dial to your number in one of the following ways.

Make outbound call using curl: Replace {AUTH_ID} with your Plivo Auth ID, {AUTH_TOKEN} with your Plivo Auth Token, and {PLIVO_NUMBER} with the number purchased from Plivo {DIAL_NUMBER} to number you want to dial

curl -i -X POST https://api.plivo.com/v1/Account/{AUTH_ID}/Call/ \
-u {AUTH_ID}:{AUTH_TOKEN} \
    -H "Content-Type: application/json" \
    -d '{"to": "{DIAL_NUMBER}","from": "{PLIVO_NUMBER}", "answer_url": "https://4964-49-37-240-174.ngrok-free.app/xml", "answer_method": "GET"}'	

Or make call using script makecall.js, Update, auth_id, auth_token, from, to and answer_url in the script