TwiMLTM Voice: <Client>

The <Dial> verb's <Client> noun specifies a client identifier to dial.

You can use up to ten <Client> nouns within a <Dial> verb to simultaneously attempt a connection with many clients at once. The first client to accept the incoming connection is connected to the call and the other connection attempts are canceled. If you want to connect with multiple other clients simultaneously, read about the <Conference> noun.

The client identifier currently may only contain alpha-numeric and underscore characters.

Noun Attributes

The <Client> noun supports the following attributes that modify its behavior:

Attribute NameAllowed ValuesDefault Value
urlany urlnone
methodGET, POSTPOST
statusCallbackEventinitiated, ringing, answered, completednone
statusCallbackany urlnone
statusCallbackMethodGET, POSTPOST

url

The 'url' attribute allows you to specify a url for a TwiML document that will run on the called party's end, after she answers, but before the parties are connected. You can use this TwiML to privately play or say information to the called party, or provide a chance to decline the phone call using <Gather> and <Hangup>. The current caller will continue to hear ringing while the TwiML document executes on the other end. TwiML documents executed in this manner are not allowed to contain the <Dial> verb.

method

The 'method' attribute allows you to specify which HTTP method Twilio should use when requesting the URL in the 'url' attribute. The default is POST.

statusCallbackEvent

When dialing out to a Client using <Dial>, an outbound call is initiated. The call transitions from the initiated state to the ringing state when the phone starts ringing. It transitions to the answered state when the call is picked up, and finally to the completed state when the call is over. With statusCallbackEvent, you can subscribe to receive webhooks for the different call progress events: initiated, ringing, answered, or completed for a given call.

The statusCallbackEvent attribute allows you to specify which events Twilio should webhook on. To specify multiple events separate them with a space: initiated ringing answered completed. If a statusCallback is provided and no status callback events are specified the completed event will be sent by default.

The initiated, ringing, and answered events have a cost of $0.0001 per event, which results in $10 for every 100,000 events. The completed event is not charged.

As opposed to creating an outbound call via the API, outbound calls created using <Dial> are initiated right away and never queued. The following shows a timeline of possible call events that can be returned and the different call statuses that a <Dial> leg may experience:

Outbound Dial call events diagram

EventDescriptionCost
initiatedThe initiated event is fired when Twilio starts dialing the call.$0.0001 per event
ringingThe ringing event is fired when the call starts ringing.$0.0001 per event
answeredThe answered event is fired when the call is answered.$0.0001 per event
completedThe completed event is fired when the call is completed regardless of the termination status: busy, canceled, completed, failed, or no-answer. If no statusCallbackEvent is specified, completed will be fired by default.No cost

statusCallback

The statusCallback attribute allows you to specify a URL for Twilio to send webhook requests to on each event specified in the statusCallbackEvent attribute.

statusCallbackMethod

The statusCallbackMethod attribute allows you to specify which HTTP method Twilio should use when requesting the URL in the statusCallback attribute. The default is POST.

Status Callback HTTP Parameters

The parameters Twilio passes to your application in its asynchronous request to the StatusCallback URL include all parameters passed in a synchronous request to retrieve TwiML when Twilio receives a call to one of your Twilio numbers. The full list of parameters and descriptions of each are in the TwiML Voice Request documentation.

When the call progress events are fired, the Status Callback request also passes these additional parameters:

ParameterDescription
CallSidA unique identifier for this call, generated by Twilio. You can use the CallSid to modify the child call by POSTing to Calls/{CallSid} with a new TwiML URL.
ParentCallSidA unique identifier for the parent call.
CallStatusA descriptive status for the call. The value is one of queued, initiated, ringing, in-progress, busy, failed, or no-answer. See the CallStatus section for more details.
CallDurationThe duration in seconds of the just-completed call. Only present in the completed event.
RecordingUrlThe URL of the phone call's recorded audio. This parameter is included only if Record=true is set on the REST API request and does not include recordings from <Dial> or <Record>. RecordingUrl is only present in the completed event.
RecordingSidThe unique ID of the Recording from this call. RecordingSid is only present in the completed event.
RecordingDurationThe duration of the recorded audio (in seconds). RecordingDuration is only present in the completed event.
TimestampThe timestamp when the event was fired, given as UTC in RFC 2822 format.
CallbackSourceA string that describes the source of the webhook. This is provided to help disambiguate why the webhook was made. On Status Callbacks, this value is always call-progress-events.
SequenceNumberThe order in which the events were fired, starting from 0. Although events are fired in order, they are made as separate HTTP requests and there is no guarantee they will arrive in the same order.

Examples

Example 1: Dialing to a client

In this example, we want to connect the current call to a client named jenny. To connect the call to jenny, use a <Dial> verb with a <Client> noun nested inside.

<?xml version="1.0" encoding="UTF-8"?>
<Response>
    <Dial>
        <Client>jenny</Client>
    </Dial>
</Response>

Example 2: Simultaneous Dialing

You can use up to ten total <Number> and <Client> nouns within a <Dial> verb to dial multiple phone numbers and clients at the same time. The first person to answer the call will be connected to the caller, while the rest of the call attempts are hung up.

<?xml version="1.0" encoding="UTF-8"?>
<Response>
    <Dial callerId="+1888XXXXXXX">
        <Number>858-987-6543</Number>
        <Client>jenny</Client>
        <Client>tommy</Client>
    </Dial>
</Response>

Example 3: Call Progress Events

In this case, we want to receive a webhook for each call progress event when dialing a Client using <Dial>.

<?xml version="1.0" encoding="UTF-8"?>
<Response>
        <Dial>
                <Client
                 statusCallbackEvent='initiated ringing answered completed'
                 statusCallback='https://myapp.com/calls/events'
                 statusCallbackMethod='POST'>
                           jenny
                </Client>
        </Dial>
</Response>