---
title: "Configure the Advanced I/O function"
url: https://docs.catalyst.zoho.com/en/tutorials/dialer-mobile-app/flutter/configure-advanced-function/
description: "Build a dialer application in Flutter using Catalyst Advanced I/O Functions, Data Store, and Twilio's Voice API to call customers from your sales team."
last_updated: 2026-11-04T10:10:44Z
service: All Services
type: tutorial
related_links:
  - name: "Advanced I/O Functions"
    url: /en/serverless/help/functions/advanced-io/
  - name: "Functions Directory Structure"
    url: /en/cli/v1/project-directory-structure/functions-directory
---

# Configure the Advanced I/O Function

Let's begin coding the Dialer app by configuring the function component.

The function's directory,`functions/dialer` contains:

   * The `index.js` main function file
   * The `catalyst-config.json` configuration file
   * Node modules
   * `[package.json](https://docs.npmjs.com/files/package.json)` and `[package-lock.json](https://docs.npmjs.com/configuring-npm/package-lock-json.html)` dependency files

### Install packages for Node.js

You will need to install two additional packages in the functions directory of your application before proceeding further.

#### **Express**

To import the [Express Node.js](https://expressjs.com/) package in the code, you must install the Express dependencies in your system. The express framework is used to manage routes and also respond to HTTP requests.

To install `Express.js` in your local machine, navigate to the function's home directory (`functions/dialer`) in your terminal and execute the following command:

```sh
 npm install express --save 
```

This will install the Express module and save the dependencies.

![install-express](https://catalyst-docs-development.zohostratus.in/images/tutorials/dialer-app/install-express.webp)

#### **Twilio**

You will also need to install the [Twilio package](https://www.npmjs.com/package/twilio) for this tutorial. The Twilio library allows you to make HTTP requests to the Twilio API. Execute the below command to add the Twilio dependencies.

```sh
 npm install twilio 
```

![install-twilio](https://catalyst-docs-development.zohostratus.in/images/tutorials/dialer-app/install-twilio.webp)

This information will also be updated in the `package.json` file.

![package-json](https://catalyst-docs-development.zohostratus.in/images/tutorials/dialer-app/package-json.webp)

Next, let's add the code in the function file. Copy the Node js code and paste it in `index.js` in the `functions/dialer` directory. You can use any IDE of your choice to work with the application's files.

> **Note**: Please go through the code given in this section to ensure you fully understand it. We will discuss the architecture of the function and the client in the next section.

**index.js**

```javascript
const express = require("express");
const app = express();
var twilio = require('twilio');
const VoiceResponse = require("twilio").twiml.VoiceResponse;
var catalyst = require('zcatalyst-sdk-node');
var YOUR_TWILIO_NUMBER = '+xxxxxxxxxx';
var accountSid = "xxxxxxxxxxxxxx";
var authToken = "7xxxxxxxxxxxxxxx8";
var twilioClient = twilio(accountSid, authToken);
var bodyParser = require('body-parser');
app.use(bodyParser.json()); // support json encoded bodies
app.use(bodyParser.urlencoded({ extended: true })); // support encoded bodies

app.post("/makeCall", async (req, res) => {
try {
var salesNumber = req.body.salesNumber;
console.log(req.body)
const catalystApp = catalyst.initialize(req);
let rowData =
{
fromNumber: req.body.phoneNumber,
toNumber: req.body.salesNumber
};
console.log(rowData)
const catalystTable = catalystApp.datastore().table('CallLog');
const data = await catalystTable.insertRow(rowData);
var url = 'https://' + req.headers.host + '/server/dialer/outbound/' + encodeURIComponent(salesNumber);

var options = {
to: req.body.phoneNumber,
from: YOUR_TWILIO_NUMBER,
url: url,
method: 'post',
statusCallbackEvent: ['answered', 'completed'],
statusCallback: 'https://' + req.headers.host + '/server/dialer/statusCheck?ROWID=' + data.ROWID,
statusCallbackMethod: 'POST'
};

twilioClient.calls.create(options).then((call) => {
res.status(200).send({ message: 'Call Initiated' });
}).catch((error) => {
console.log(error);
res.status(500).send({ "error": error });
});
} catch (e) {
console.log("Exception while making a Call ::" + e);
res.status(500).send({ "error": 'Internal Server Error Occured. Please Try again after sometime.' });
}
});

app.post('/outbound/:salesNumber', function (req, res) {

try {
var salesNumber = req.params.salesNumber;
var twimlResponse = new VoiceResponse();
twimlResponse.say('Thanks for trying out the Catalyst Dialer App. Please hold on so that we can connect with your Customer... ', { voice: 'alice' });
twimlResponse.dial(salesNumber);
res.status(200).send(twimlResponse.toString());
} catch (e) {
console.log("Exception while making Outbound Call ::" + e);
res.status(500).send({ "error": 'Internal Server Error Occured. Please Try again after sometime.' });
}
});

app.post('/statusCheck', async (req, res) => {

try {
const catalystApp = catalyst.initialize(req);
if (req.body.CallStatus === "completed") {
let updatedRowData = {
callDuration: req.body.CallDuration,
callStatus: req.body.CallStatus,
calledCountry: req.body.CalledCountry,
calledState: req.body.CalledState,
timeOfCall: req.body.Timestamp,
ROWID: req.body.ROWID
};
console.log(updatedRowData)
const catalystTable = catalystApp.datastore().table('CallLog');
await catalystTable.updateRow(updatedRowData);
}
res.status(200).send(' StatusCheck Completed');
} catch (e) {
console.log("Exception while checking status :: " + e);
res.status(500).send({ "error": 'Internal Server Error Occured. Please Try again after sometime.' });
}
});

app.get('/getLogs', async function (req, res) {

try {
const catalystApp = catalyst.initialize(req);
const query = 'SELECT callDuration,callStatus,calledCountry,timeOfCall,fromNumber,toNumber FROM CallLog';
const queryResult = await catalystApp.zcql().executeZCQLQuery(query);
res.status(200).send(queryResult);
} catch (e) {
console.log("Exception while getting Call Logs ::" + e);
res.status(500).send({ "error": 'Internal Server Error Occured. Please Try again after sometime.' });
}

});

module.exports = app;

```

> **Note**:Please make sure you add your Twilio accountID, associated Twilio phone number ,and auth token values in lines 6, 7, and 8.

The functions directory is now configured.