Swift Networking
Network.framework is Apple's modern networking API for TCP/UDP connections, replacing BSD sockets with smart connection establishment, user-space networking, and seamless mobility handling.
Reference Loading Guide
ALWAYS load reference files if there is even a small chance the content may be required. It's better to have the context than to miss a pattern or make a mistake.
| Reference | Load When |
|---|---|
| Getting Started | Setting up NWConnection for TCP/UDP, choosing between APIs |
| Connection States | Handling .waiting, .ready, .failed transitions |
| iOS 26+ Networking | Using NetworkConnection with async/await, TLV framing, Coder protocol |
| Migration Guide | Moving from sockets, CFSocket, SCNetworkReachability, URLSession |
| Troubleshooting | Debugging timeouts, TLS failures, connection issues |
Core Workflow
- Choose transport (TCP/UDP/QUIC) based on use case
- Create NWConnection (iOS 12+) or NetworkConnection (iOS 26+)
- Set up state handler for connection lifecycle
- Start connection on appropriate queue
- Send/receive data with proper error handling
- Handle network transitions (WiFi to cellular)
When to Use Network.framework vs URLSession
- URLSession: HTTP, HTTPS, WebSocket, simple TCP/TLS streams
- Network.framework: UDP, custom protocols, low-level control, peer-to-peer, gaming
Common Mistakes
- Ignoring state handlers — Creating an NWConnection without a state change handler means you never learn when it's ready or failed. Always implement the state handler first.
- Blocking the main thread — Never call
receive()on the main queue. Use a background DispatchQueue or Task for all network operations. - Wrong queue selection — Using the wrong queue (UI queue for network work, or serial queue for concurrent reads) causes deadlocks or silent failures. Always explicit your queue choice.
- Not handling network transitions — WiFi/cellular switches or network loss aren't always detected automatically. Implement viability checks and state monitoring for robust apps.
- Improper error recovery — Network errors need retry logic with backoff. Immediately failing on transient errors (timeouts, temporary loss) creates poor UX.