Swift Networking

Reference Loading Guide

.waiting

.ready

.failed

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.