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.getCallClient(). Calling is not enabled by default.

Enable calling with the following method before starting the SinchClient:


Set up an app-to-app call

Use the CallClient to start the call (the callUser method). Pass the user identifier of the callee (the user receiving the call) to the call method, so that Sinch services can connect the call to the callee.

CallClient callClient = sinchClient.getCallClient();
Call call = callClient.callUser("<remote user id>");
// Or for video call: Call call = callClient.callUserVideo("<remote user id>");

A call object is returned, containing details about the participants in the call, call details such as start time, call state, and possible errors.

Assuming the callee’s device is available, the method onCallProgressing is called on the CallListener. It notifies the application that the outgoing call is progressing. If a progress tone should be played, this is where it should be started.

When the other party answers, the onCallEstablished method is called. Now, the users can start talking. If a progress tone was previously played, it should be stopped now.

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 callPhoneNumber method on the CallClient object. Sufficient funds must be available on the Sinch account and a valid phone number specified for the call to connect successfully. The phone number should be specified according to the E.164 number formatting ( ) recommendation and should be prefixed with a ‘+’. To call the US phone number 415 555 0101, the phone number should be specified as "+14155550101." The ‘+’ is the required prefix and the US country code ‘1’ prepended to the local subscriber number.

Placing an app-to-phone call requires a developer account with credits. Topping up credits can be done on the Account page. Credits are used each time an app-to-phone call is placed and the balance history is updated after each call.

App-to-phone calls can be tested by calling the following test number: +46000000000. When placing a call to this number, you will hear a voice prompt stating that the call has been connected, and shortly after that the call will automatically be ended.

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 the callSip method on the CallClient object. 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 reported 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.

CallClient callClient = sinchClient.getCallClient();
Call call = callClient.callConference("<conferenceId>");

It's also possible to connect users to a conference call via the Sinch REST API.

Handle incoming calls

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

Add a CallClientListener to the CallClient to act on the incoming calls. The CallClientListener is notified using onIncomingCall as calls come in to the device.

CallClient callClient = sinchClient.getCallClient();

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.

public void onIncomingCall(CallClient callClient, Call call) {
    // Start playing ringing tone

    // Add call listener

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.

Incoming video call

When incoming call is a video call, the onIncomingCall callback will be executed, just like for the incoming audio call. The CallDetails object provides a isVideoOffered() method to check whether the call offers a video track. See the [Video calling] section for details on how to add video views.

Answer incoming call

To answer the call, use the answer method on the call to accept it. If a ringtone was previously played, it should be stopped now.

User presses the answer button:

// User answers the call

// Stop playing ringing tone

Now, the clients on both ends establish the connection. When the call is established and the voice streams are running in both directions, the onCallEstablished listener method is called.

Decline incoming call

If the call shouldn't be answered, use the hangup method 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:

// User does not want to answer

// Stop playing ringing tone

Disconnecting a Call

When the user wants to disconnect an ongoing call, use the hangup method. Either user taking part in a call can disconnect it.

Hanging up a call:


When either party disconnects a call, the application is notified using the call listener method 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:

// Starting a call
Call call = callClient.callUser("<remote user id>");

// User changed his/her mind, let’s hangup

Volume control

To make sure that the volume of the call can be modified by the hardware volume controls, setVolumeControlStream(AudioManager.STREAM_VOICE_CALL) must be called on the Activity where the call is handled. Make sure that volumeControlStream is reset to a suitable value when the call has ended.

For example, after creating a call (using CallClient.callUser) or when answering a call (using Call.answer()) you should call setVolumeControlStream(AudioManager.STREAM_VOICE_CALL);.

When the call ends, set the volume control stream back to it’s previous value. For example in your implementation of CallListener:

public void onCallEnded(Call call) {