Networking Migration Reference

Step-by-step guides for moving between networking APIs. It starts with a decision tree for whether to migrate at all, then covers three migration paths with before/after code, mapping tables, and the benefits of each.

When to Use This Reference

Use this reference when you need to:

• Decide whether to migrate or stay with your current API
• Migrate from BSD sockets, CFSocket, or NSStream to NWConnection
• Replace SCNetworkReachability with NWPathMonitor
• Upgrade from NWConnection to NetworkConnection (iOS 26+)
• Replace a URLSession stream task with NetworkConnection
• Understand the mapping between old and new APIs

Example Prompts

Questions you can ask your assistant that will draw from this reference:

• "How do I migrate from BSD sockets to NWConnection?"
• "What's the equivalent of NWConnection's stateUpdateHandler in NetworkConnection?"
• "How do I replace completion handlers with async/await for networking?"
• "Should I migrate from a URLSession stream task to NetworkConnection?"
• "What are the benefits of moving to NetworkConnection on iOS 26?"
• "How do I replace [weak self] patterns when migrating to async/await?"
• "Is NWConnection deprecated?"

What's Covered

• Do I need to migrate? – A decision tree by current API: URLSession for HTTP stays, BSD sockets and CFSocket/NSStream move to NWConnection, SCNetworkReachability moves to NWPathMonitor, and working NWConnection code can stay because it isn't deprecated
• BSD sockets to NWConnection – Mapping table for socket/connect/send/recv/bind/listen/accept and their NWConnection equivalents, with complete before/after code
• NWConnection to NetworkConnection – Completion handlers to async/await, stateUpdateHandler to the onStateUpdate closure, manual JSON to the built-in Coder protocol, custom framers to built-in TLV
• URLSession stream task to NetworkConnection – When to migrate (UDP, custom protocols, low-level control) and when to stay (HTTP, WebSocket, caching)
• Line count reductions – 20 to 10 lines and 30 to 15 lines in the examples
• Memory management changes – Why async/await removes the need for [weak self]

Documentation Scope

This page documents the networking-migration skill (in the axiom-networking suite), the migration guides your assistant uses when helping you move between networking API generations. The skill contains complete before/after examples for each migration path.

Related

• networking – Modern networking patterns and architecture decisions
• networking-legacy – NWConnection patterns for apps that support iOS 12–18
• network-framework-ref – Complete Network.framework API reference
• networking-diag – Troubleshooting connection failures

Resources

WWDC: 2018-715, 2025-250

Docs: /network, /network/nwconnection