swift-networking

name	swift-networking
description	Use when implementing Network.framework connections (NWConnection, NetworkConnection), debugging connection failures, migrating from sockets/URLSession streams, or handling network transitions. Covers UDP/TCP patterns, structured concurrency networking (iOS 26+), and common anti-patterns.

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

1. Choose transport (TCP/UDP/QUIC) based on use case
2. Create NWConnection (iOS 12+) or NetworkConnection (iOS 26+)
3. Set up state handler for connection lifecycle
4. Start connection on appropriate queue
5. Send/receive data with proper error handling
6. 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

1. 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.

2. Blocking the main thread — Never call receive() on the main queue. Use a background DispatchQueue or Task for all network operations.

3. 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.

4. Not handling network transitions — WiFi/cellular switches or network loss aren't always detected automatically. Implement viability checks and state monitoring for robust apps.

5. Improper error recovery — Network errors need retry logic with backoff. Immediately failing on transient errors (timeouts, temporary loss) creates poor UX.