Getting started with Stringee Call2 API using iOS SDK

Step 1: Prepare

When using Stringee Call API for the first time, you must have a Stringee account. If you do not have a Stringee account, sign up for free here: https://developer.stringee.com/account/register
Create a Project on Stringee Dashboard
Buy a Number (optional) For app-to-phone, phone-to-app calling, buy a Number from Dashboard. If you only need app-to-app calling, skip this step.
Configure answer_url

For more information on answer_url, read Stringee Call API Overview. You can view answer_url sample code here: https://github.com/stringeecom/server-samples/tree/master/answer_url

Configure Project's answer_url: To make an app-to-app, app-to-phone call, configure your Project's answer_url

If you do not have answer_url, to speed things up you can use the following Project's answer_url:

Project's answer_url for App-to-App call:

https://developer.stringee.com/scco_helper/simple_project_answer_url?record=false&appToPhone=false

Project's answer_url for App-to-Phone call:

https://developer.stringee.com/scco_helper/simple_project_answer_url?record=false&appToPhone=true

(Source code here: https://github.com/stringeecom/server-samples/blob/master/answer_url/php/project_answer_url.php)

When building an application, you should use your own answer_url.

Configure Number's answer_url: To receive a phone-to-app call, configure your Number's answer_url

If you do not have a answer_url, to speed things up you can use the following Number's answer_url:

Number's answer_url for Phone-to-App call (The call is routed to Your App which authenticated by USER_ID):

https://developer.stringee.com/scco_helper/simple_number_answer_url?record=true&phoneToPhone=false&to_number=USER_ID

Number's answer_url for Phone-to-Phone call (The call is routed to TO_NUMBER):

https://developer.stringee.com/scco_helper/simple_number_answer_url?record=true&phoneToPhone=true&stringeeNumber=STRINGEE_NUMBER&to_number=TO_NUMBER

(Source code here: https://github.com/stringeecom/server-samples/blob/master/answer_url/php/number_answer_url.php)

When building an application, you should use your own answer_url.

Step 2: Add SDK to Project

Distribution notice: Starting in June 2026, new versions of the Stringee iOS SDK are released exclusively through Swift Package Manager (SPM). CocoaPods and manual distributions are retained for legacy integrations only and no longer receive version updates.

Swift Package Manager (recommended)

The SPM package requires iOS 13.0 or later and Swift tools 5.9 or later.

Open your iOS project in Xcode.
Select File > Add Package Dependencies....
Enter the package URL:

https://github.com/stringeecom/Stringee-iOS-SDK-SPM.git

Select the version you want to use.
Add the Stringee product to your app target.

Swift Package Manager downloads Stringee.xcframework and its required dependencies automatically when resolving the package. For Package.swift configuration and the latest version details, see the Stringee iOS SDK SPM repository.

CocoaPods (legacy)

Edit your project's Podfile

The simplest way to import the SDK into an iOS project is with CocoaPods. Open your project's Podfile and add this line to your app's target:

pod 'Stringee'

Then from the command line run:

pod install --repo-update

If you're new to CocoaPods, see their official documentation for info on how to create and use Podfiles.

In the "Build Settings" tab -> "Other linker flags" add "$(inherited)" flag
In the "Build Settings" tab -> "Enable bitcode" select "NO"

Manual (legacy)

To add the SDK in Xcode:

Download the SDK: https://developer.stringee.com/download
Unzip the archive to your project home directory
Open your application's Xcode project.
Create a Frameworks group in your project (if you do not have one).
Open your project home directory using Finder.
Drag the Stringee.framework into the Frameworks group of Xcode's Project Navigator. In the displayed dialog, choose "Create groups" and select "Copy items if needed".

Open Xcode's Build Settings tab in your project.
Add $(SRCROOT) to the project's Framework Search Paths setting.

Configure Xcode Project

Add the following libraries and frameworks to Target -> "Build Phases" -> "Link Binary With Libraries":

AVFoundation.framework
GLKit.framework
AudioToolBox.framework
VideoToolBox.framework
libicucore.tbd
libstdc++.tbd (or libc++.tbd with Xcode 10)

In the "Build Settings" tab -> "Other linker flags" add "-ObjC" flag

In the "Build Settings" tab -> "Enable bitcode" select "NO"

Step 3: Edit Info.plist

Right-click the information property list file (Info.plist) and select Open As -> Source Code
Insert the following XML snippet into the body of your file just before the final element:

<key>NSCameraUsageDescription</key>
<string>$(PRODUCT_NAME) uses Camera</string>
<key>NSMicrophoneUsageDescription</key>
<string>$(PRODUCT_NAME) uses Microphone</string>

Step 4: Connect to Stringee Server

In order to connect to Stringee Server, 3-parties authentication is required as described here: Client authentication

For testing purpose, go to Dashboard -> Tools -> Generate Access token and generates an access_token. In production, the access_token should be generated by your server. This is a sample code to generate an access token: https://github.com/stringeecom/server-samples/tree/master/access_token

Add a line to import the Stringee library:

#import <Stringee/Stringee.h>

Implements the StringeeConnectionDelegate protocol

In .h file

@interface ViewController : UIViewController <StringeeConnectionDelegate>

@property(strong, nonatomic) StringeeClient *stringeeClient;

@end

In .m file

- (void)requestAccessToken:(StringeeClient *)stringeeClient {
    NSLog(@"requestAccessToken");
}

- (void)didConnect:(StringeeClient *)stringeeClient isReconnecting:(BOOL)isReconnecting {
    NSLog(@"Successfully connected to Stringee Server, user ID: %@", stringeeClient.userId);
}

- (void)didDisConnect:(StringeeClient *)stringeeClient isReconnecting:(BOOL)isReconnecting {
    NSLog(@"didDisConnect");
}

- (void)didFailWithError:(StringeeClient *)stringeeClient code:(int)code message:(NSString *)message {
    NSLog(@"Failed connection to Stringee Server with error: %@", message);
}

Start connecting

NSString *accessToken = @"...";

self.stringeeClient = [[StringeeClient alloc] initWithConnectionDelegate:self];
[self.stringeeClient connectWithAccessToken:accessToken];

Step 5: Make a call

When the client connects to Stringee Server, instantiate a StringeeCall2 object and call the makeCallWithCompletionHandler method:

StringeeCall2 *stringeeCall2 = [[StringeeCall2 alloc] initWithStringeeClient:self.stringeeClient from:@"+1273065979" to:@"+1909982888"];
[stringeeCall2 makeCallWithCompletionHandler:^(BOOL status, int code, NSString * message, NSString *data){
        NSLog(@"Make call result: code=%d, message: %@", code, message);
}];

Handle the call type

The type of the outgoing call (app-to-app or app-to-phone) is decided by Your Server via the project's answer_url. Hence, you should be able to complete it independently. However, we offer an easy method for you to implement quickly:

stringeeCall2.customData = @"custom";

"custom" is a customizable text that be sent to Your Server via the project's answer_url. You can set it as: {'type': 'app-to-app'}, {'type':'app-to-phone'} or any other texts you want. Your Server will check this text to determine whether the call is app-to-app or app-to-phone.

Step 6: Receiving call events

Implement the StringeeCallDelegate protocol

#import <Stringee/Stringee.h>

@interface ViewController : UIViewController <StringeeConnectionDelegate, StringeeCall2Delegate>

@property(strong, nonatomic) StringeeClient *stringeeClient;

@end

in .m file:

//----------- StringeeCall2Delegate -->

- (void)didChangeSignalingState2:(StringeeCall2 *)stringeeCall2 signalingState:(SignalingState)signalingState reason:(NSString *)reason sipCode:(int)sipCode sipReason:(NSString *)sipReason {
    NSLog(@"signalingState: %d", signalingState);
}

- (void)didChangeMediaState2:(StringeeCall2 *)stringeeCall2 mediaState:(MediaState)mediaState {
    NSLog(@"mediaState: %d", mediaState);
}

- (void)didReceiveLocalStream2:(StringeeCall2 *)stringeeCall2 {
    NSLog(@"didReceiveLocalStream");
}

- (void)didReceiveRemoteStream2:(StringeeCall2 *)stringeeCall2 {
    NSLog(@"didReceiveRemoteStream");
}

- (void)didHandleOnAnotherDevice2:(StringeeCall2 *)stringeeCall2 signalingState:(SignalingState)signalingState reason:(NSString *)reason sipCode:(int)sipCode sipReason:(NSString *)sipReason {
    NSLog(@"didAnsweredOnOtherDevice %d", signalingState);
}

//----------- StringeeCall2Delegate <--

and set delegates for stringeeCall:

stringeeCall2.delegate = self;

Step 7: Receiving incoming call event

Implement the StringeeIncomingCallDelegate protocol

#import <Stringee/Stringee.h>

@interface ViewController : UIViewController <StringeeConnectionDelegate, StringeeCall2Delegate, StringeeIncomingCallDelegate>

@property(strong, nonatomic) StringeeClient *stringeeClient;

@end

in .m file:

- (void)incomingCallWithStringeeClient:(StringeeClient *)stringeeClient stringeeCall2:(StringeeCall2 *)stringeeCall2 {
    NSLog(@"incomingCallWithStringeeClient, from: %@, to: %@", stringeeCall2.from, stringeeCall2.to);
}

and set incomingCallDelegate for stringeeClient:

self.stringeeClient.incomingCallDelegate = self;

Step 8: Answer a call

When the client receives an incoming call

- (void)incomingCallWithStringeeClient:(StringeeClient *)stringeeClient stringeeCall2:(StringeeCall2 *)stringeeCall2 {
    NSLog(@"incomingCallWithStringeeClient, from: %@, to: %@", stringeeCall2.from, stringeeCall2.to);    
    stringeeCall2.delegate = self;
}

Call the following method to initialize resources:

    [stringeeCall2 initAnswerCall];

Call the following method to answer and start the conversation:

    [stringeeCall2 answerCallWithCompletionHandler:^(BOOL status, int code, NSString *message) {
        NSLog(@"%@", message);
    }];

Step 9: Hanging up a call

Call the following method to Hang up a call.

    [stringeeCall2 hangupWithCompletionHandler:^(BOOL status, int code, NSString *message) {
        NSLog(@"%@", message);
    }];

Step 10: Reject a call

Call the following method to reject a call.

    [stringeeCall2 rejectWithCompletionHandler:^(BOOL status, int code, NSString *message) {
        NSLog(@"%@", message);
    }];

Step 11: Video call

A Stringee call is a voice call by default. If you want to make a video call, you must assign:

stringeeCall2.isVideoCall = YES;

Display local video

- (void)didReceiveLocalStream2:(StringeeCall2 *)stringeeCall2 {
    dispatch_async(dispatch_get_main_queue(), ^{
        [stringeeCall2.localVideoView setFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height)];
        [self.view insertSubview:stringeeCall2.localVideoView atIndex:0];
    });
}

Display remote video

-(void) didReceiveRemoteStream2:(StringeeCall2 *)stringeeCall2 {
    dispatch_async(dispatch_get_main_queue(), ^{
        [stringeeCall2.remoteVideoView setFrame:CGRectMake(0, 0, self.containRemoteView.bounds.size.width, self.containRemoteView.bounds.size.height)];
        [self.containRemoteView addSubview:stringeeCall2.remoteVideoView];
    });
}

Loudspeaker

- (void)didChangeMediaState2:(StringeeCall2 *)stringeeCall2 mediaState:(MediaState)mediaState {
    dispatch_async(dispatch_get_main_queue(), ^{
        if (mediaState == MediaStateConnected) {
            [[StringeeAudioManager instance] setLoudspeaker:YES];
        }
    });
}

Step 12: Sample

You can view the full version of this sample app on GitHub: https://github.com/stringeecom/ios-sdk-samples/tree/master/CallkitSample-Call2

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