Networking with NSURLSession

Networking is one of critical features for every iOS app.In iOS 9, there are some important update for networkings and related framework NSURLSession

App Transport Security (ATS)

• Disallow cleartext HTTP URL locals
• Encourage secure connections
• Defaults to stronger security
• Allows exception via app's info.plist

Sample info.plist for exception http protocol

More explanation and keys on ATS

ATS only active when the app is built with iOS 9 SDK for iOS 9 and OX El Capitan

Automatic convert from http:// to https://

Use NSAllowsArbitraryLoads for quick triage (allow load all http and https)

CFNETWORK_DIAGNOSTICS=1 to log all error from system networking

NSURLSession supports HTTP/2 automatically and nothing to change in code

NSURLSession on watchOS

NSURLSession availabe in watchOS 2

Best Practices

Download the minimal assets

• small screen
• limited bandwidth

Since the apps run very short time

• send small amounts of data
• use background upload and downloads for larger content

NSURLConnection is deprecated in OS 10.11 and iOS 9.0

• existing apps using it will still work
• New features only available in NSURLSession
• Not supported on watchOS

New features on NSURLSession

• shared cookies storage
• NSURLSessionStreamTask
  • supports TCP/IP connections with hostnames and ports
  • NSURLSession configuration and session delegates applies
  • support TLS
  • convertion from NSStream