# Voice calling

Voice calling with javascript Voice and Video SDK. Set up calling between applications, from application to phone, app to SIP and conference calls. Get more information here.

The Sinch SDK supports four types of calls: *app-to-app (audio or video)*, *app-to-phone*, *app-to-sip* and *conference* calls. The *CallClient* is the entry point for the calling functionality of the Sinch SDK.

Calls are placed through the *CallClient* and events are received using the *CallClientListener*. The call client is owned by the SinchClient and accessed using `sinchClient.callClient`.

## Set up an *App-to-App* call

Use the [CallClient.callUser()](https://download.sinch.com/js/latest/reference/interfaces/CallClient.html#calluser) method so Sinch can connect the call to the callee.


```javascript
var callClient = sinchClient.callClient;
var call = callClient.callUser('<remote user id>');
// Video call:
// var call = callClient.callUserVideo('<remote user id>');
call.addListener(...);
```

The returned call object includes participant details, start time, state,
and possible errors.

Assuming the callee’s device is available,
[CallListener.onCallProgressing()](https://download.sinch.com/js/latest/reference/interfaces/CallListener.html#oncallprogressing)
is invoked. If you play a progress tone, start it here.
When the callee receives the call,
[CallListener.onCallRinging()](https://download.sinch.com/js/latest/reference/interfaces/CallListener.html#oncallringing)
fires. This indicates the callee’s device is ringing.
When the other party answers,
[CallListener.onCallAnswered()](https://download.sinch.com/js/latest/reference/interfaces/CallListener.html#oncallanswered)
is called. Stop any progress tone.
Once full audio connectivity is established,
[CallListener.onCallEstablished()](https://download.sinch.com/js/latest/reference/interfaces/CallListener.html#oncallestablished)
is emitted. Users can now talk.

Typically, connectivity is already established when the call is answered, so
`onCallEstablished` may follow immediately after `onCallAnswered`.
On poor networks, it can take longer—consider showing a “connecting”
indicator.

Important
For *App-to-App* calls, you must enable managed push by calling `sinchClient.setSupportManagedPush()`, even if you are the caller. See the full setup in [Push notifications](/docs/in-app-calling/js/push-notifications).

## Set up an *App-to-Phone* call

An *app-to-phone* call is a call that's made to a phone on the regular telephone network. Setting up an *app-to-phone* call is not much different than setting up an *app-to-app* call. Instead of invoking the `callUser` method, invoke the [CallClient.callPhoneNumber()](https://download.sinch.com/js/latest/reference/interfaces/CallClient.html#callphonenumber) method and pass an E.164 number prefixed with `+`. For example, to call the US phone number 415 555 0101, specify `+14155550101`. The `+` is the required prefix with the US country code `1` prepended to the local subscriber number.

### Presenting a number to the destination you are calling

Mandatory step!
You must provide a CLI (Calling Line Identifier) or your call will fail.

You need a number from Sinch so you can provide a valid CLI to the handset you are calling. If you have a trial account, you can use the [test number](https://community.sinch.com/t5/Virtual-Numbers/How-can-I-activate-my-free-number-for-testing/ta-p/8578) that is available for free. If you have already upgraded your account, you can purchase a number to use on the [dashboard](https://dashboard.sinch.com/numbers/your-numbers).

Specify your CLI during building SinchClient by using [callerIdentifier](https://download.sinch.com/js/latest/reference/interfaces/SinchClientBuilder.html#calleridentifier-1) method.

Note:
When your account is in trial mode, you can only call your [verified numbers](https://dashboard.sinch.com/numbers/verified-numbers). If you want to call any number, you need to upgrade your account!

Credits Required
Remember, placing an *App-to-Phone* call requires that your Sinch account has sufficient credits. Add credits on your [Account](https://dashboard.sinch.com/account) page. Credits are used each time an *App-to-Phone* call is placed and your account balance is updated after each call.

Testing DTMF
In *App-to-Phone* scenario, it's possible to issue DTMF sequences using Sinch SDK. Note that if the receiving end of the call is an iOS device, you might have to disable *VoLTE* ("Voice over LTE") option in the settings of the phone at the receiving end of the call in order to be able to hear DTMF tones.

## Set up an *App-to-sip* call

An *app-to-sip* call is a call that's made to a SIP server. Setting up an *app-to-sip* call is not much different from setting up an *app-to-app* call. Instead of invoking the `callUser` method, invoke [CallClient.callSip()](https://download.sinch.com/js/latest/reference/interfaces/CallClient.html#callsip). The SIP identity should be in the form `user@server`. By convention, when passing custom headers in the SIP call, the headers should be prefixed with `x-`. If the SIP server reports any errors, the `CallDetails` object will provide an error with the `SIP` error type.

## Set up a *Conference* call

A *conference* call can be made to connect a user to a conference room where multiple users can be connected at the same time. The identifier for a conference room may not be longer than 64 characters.


```javascript
var callClient = sinchClient.callClient;
var call = callClient.callConference('<conferenceId>');
call.addListener(...);
```

It is also possible to connect users to a conference call via the [Sinch REST API](/docs/voice/api-reference/voice/callouts/).

## Selecting audio input device

To select a specific audio input device, set the `deviceId` constraint via
[CallClient.setAudioTrackConstraints()](https://download.sinch.com/js/latest/reference/interfaces/CallClient.html#setaudiotrackconstraints).


```javascript
sinchClient.callClient.setAudioTrackConstraints({
  deviceId: { exact: <yourVideoDeviceId> },
});
```

For a full sample of input/output device selection, see the
[reference app](https://github.com/sinch/rtc-reference-applications/tree/master/javascript/samples).

## Handle incoming calls

To answer calls, the application must be notified when the user receives an incoming call.

Add a [CallClientListener](https://download.sinch.com/js/latest/reference/interfaces/CallClientListener.html) to `CallClient` to act on incoming calls. When a call arrives, [CallClientListener.onIncomingCall()](https://download.sinch.com/js/latest/reference/interfaces/CallClientListener.html#onincomingcall) is executed.


```javascript
var callClient = sinchClient.callClient;
callClient.addListener(...);
```

When the incoming call method is executed, the call can either be connected automatically without any user action, or it can wait for the user to press the answer or the hangup button. If the call is set up to wait for a user response, we recommended that a ringtone is played to notify the user that there is an incoming call.


```javascript
onIncomingCall = (callClient, call) => {
    // Start playing ringing tone
    ...

    // Add call listener
    call.addListener(...);
}
```

To get events related to the call, add a call listener. The call object contains details about participants, start time, potential error codes, and error messages.

### Receiving Calls from PSTN or SIP (Phone-to-App / SIP-to-App)

The Sinch SDK supports receiving incoming calls that originate from the PSTN (regular phone network) or from SIP endpoints.
When a call arrives at a Sinch voice number or via SIP origination, the Sinch platform triggers an **Incoming Call Event (ICE)** callback to your backend.
Out platform can then route this call to an in-app user by responding with the `connectMxp` SVAML action.

#### Prerequisites

1. Rent a voice number from the [Sinch Build Dashboard](https://dashboard.sinch.com/numbers/overview) and assign it to your application, OR configure SIP origination for your application
2. Configure a callback URL in your app's Voice settings where Sinch will send call-related events
3. Implement the ICE callback handler in your backend to route calls to the appropriate app user


#### Backend Implementation

When a PSTN or SIP call comes in, respond to the ICE callback with a `connectMxp` action to route the call to an app user:


```json
{
  "action": {
    "name": "connectMxp",
    "destination": {
      "type": "username",
      "endpoint": "target-user-id"
    }
  }
}
```

### Incoming video call

When an incoming call is a video call, the [CallClientListener.onIncomingCall()](https://download.sinch.com/js/latest/reference/interfaces/CallClientListener.html) section for details on how to add video views.

### Answer incoming call

To answer the call, use the
[Call.answer()](https://download.sinch.com/js/latest/reference/interfaces/Call.html#answer)
method on the call to accept it. If a ringtone was previously played, it
should be stopped now.

User presses the answer button:


```javascript
// User answers the call
call.answer();

// Stop playing ringing tone
```

### Decline incoming call

If the call shouldn't be answered, use
[Call.hangup()](https://download.sinch.com/js/latest/reference/interfaces/Call.html#hangup)
on the call to decline. The caller is notified that the incoming call was
denied. If a ringtone was previously played, it should be stopped now.

User presses the hangup button:


```javascript
// User doesn't want to answer
call.hangup();

// Stop playing ringing tone
...
```

## Disconnecting a Call

When the user wants to disconnect an ongoing call, use
[Call.hangup()](https://download.sinch.com/js/latest/reference/interfaces/Call.html#hangup)
method. Either user taking part in a call can disconnect it.

Hanging up a call:


```javascript
call.hangup();
```

When either party disconnects a call, the application is notified using the
call listener method
[CallListener.onCallEnded()](https://download.sinch.com/js/latest/reference/interfaces/CallListener.html#oncallended).
This allows the user interface to be updated, an alert tone to be played, or
similar actions to occur.

A call can be disconnected before it has been completely established.

Hanging up a connecting call:


```javascript
// Starts a call asynchronously
var call = callClient.callUser('<remote user id>');

// User changed his/her mind, let’s hangup
call.hangup();
```