Networking and communication

Send and receive data and files across the network

Apps connect people to their friends and to the services they use in their daily lives. Many system frameworks use network-based services in their implementation, but you might also need to download files, communicate with RESTful endpoints, or support audio and video conversations over the network. When you do, the system frameworks provide the APIs you need to send and receive data over the network.

Send and receive data and files across the network

When you want to send or receive data or files over the network, the URL Loading System provides the most robust option for making your requests. This system offers a straightforward API, which you use to:

• Downloading files from websites files from a URL.

• Fetching website data into memory or Uploading data to a website data to a website or RESTful endpoint.

• Uploading streams of data to a server.

• Downloading files in the background while your app is inactive.

The URL loading system uses a session-based approach to manage network requests. Each session’s configuration tells the system how to manage network requests and any changes that might occur. For example, you might URLSessionConfiguration to download large files only over Wi-Fi instead of a cellular network. After creating the session, schedule tasks to send or receive the data you want. The system performs the tasks you schedule, using the session’s configuration data to manage authentication credentials, determine how to use caches and cookies, and select appropriate networks. To keep your app informed of progress, the session reports updates to a delegate object you provide.

Because the URL loading system is part of the Foundation, it’s available to all apps and is portable across different devices.

Customize your app’s network-based communication

Modern networking requires many different communication protocols, and it’s important to know which ones to use for a given connection to a server. Technologies like the URL Loading System handle much of this complexity for you, providing a simple API to send and receive resources. However, there might be times when you need to manage a connection yourself to accommodate performance requirements or network behaviors. For example:

• You might want to minimize latency when sending game data to other devices.

• You might need multicast support for a streaming app, or want to prevent buffering during a live broadcast.

• You might want to handle transitions between different networks yourself in a mail or messaging app.

For more direct control over your app’s network requests, adopt the Network framework. Use this framework to establish connections to servers and other devices using standard protocols like QUIC, TCP, UDP, or custom protocols you define. The framework offers ways to tune connections for your specific needs. It handles network-related changes gracefully, making it easy to track changes to network availability and move your connection to a more reliable network. It also supports the security and privacy options you need to protect the data you send.

To initiate a connection to another device, create an NWConnection object and configure it with the endpoint and parameters. The endpoint provides the address of the other device, but you can also specify Bonjour services and other values. When you start a connection, the system evaluates network conditions and selects the network that best meets your requirements. On the server side, a NWListener object responds to a connection request and sends responses from your server back to the client.

Extend the core networking capabilities of a device

If your app has custom networking requirements, you can augment the core network’s capabilities in many ways. For example:

• Create custom Wi-Fi configuration.

• Implement a helper to Hotspot helper.

• Create and manage Network Extension configurations, or implement your own.

• Create a Relays.

• Implement on-device Network Extension or URL filters filters.

• Create and manage system-wide Network Extension.

• Create your own Local push connectivity on a local network.

Implement the capabilities you need using the types of the Network Extension framework. Most features require you to put your code in an app extension, which you deliver to customers inside an app. Not all features are available on all platforms, so check the documentation to make sure the feature you want is available.

Advertise a device using Bonjour

Bonjour is Apple’s implementation of zero-configuration networking, a process that simplifies device setup and interactions on a local network. With Bonjour, apps can browse for devices on the network without knowing specific network addresses. Bonjour provides a list of available devices that support the requested capability. For example, the system printing panel looks for printers on the local network and presents them as relevant targets for a print job.

To make your app’s custom capabilities available on the network, use the Network framework to advertise them using Bonjour. Specifically, configure a NWListener to handle incoming requests from other devices. To place a request to your capability, clients configure an NWConnection object with the specific NWEndpoint you advertise using Bonjour.

Add dialing and conversation features to your app

If your app manages its own Voice-over-IP (VoIP) services, LiveCommunicationKit supports your app’s conversation infrastructure. Use that framework to notify the system of your app’s status, which the system uses to handle inbound calls. For example, if someone is on a call when a new call comes in, the system might ask the person if they want to hang up the current call and accept the new one. If your app manages calls, but doesn’t provide its own VoIP services, manage conversations using LiveCommunicationKit, which routes conversations to the appropriate app.

In some regions, the owner of a device designates one app to handle incoming and outgoing conversations. When multiple apps are present, the system needs to know which one to use for incoming conversations. On iPhone, the Phone app is typically the default calling and dialer app, but people can choose different apps. If you’re building a conversation app, adopt the LiveCommunicationKit framework to prepare your app to become the Preparing your app to be the default dialer app and Preparing your app to be the default calling app app. In addition to handling calls, the default dialer app has access to the conversation history on the person’s device, as well as other benefits.