103: Don’t Hate Us, Nolan

iOhYes

Discussion

Pushing info to clients

• Long Polling
  • Client sends request to server, waits for response or timeouts (Loop)
  • Can send and receive information, but not full-duplex
  • iOS Implementation
    • NSURLConnection sendSynchronousRequest
  • Common uses
    • Fallback from Websockets and SSE when streams are unreliable or impractical
• HTTP Streams
  • Can only push information to your client
  • If you need to send info back to server use standard rest approach
  • Transported over simple HTTP
  • Built in support for re-connection and event-id
  • iOS Implementation
    • Server Sent Events (SSE)
    • NSURLSession, NSInputStream, NSSteamEvent
    • Setup the connection
    • Implement code to handleEvents from the input stream
  • Common uses
    • Stock ticker streaming
    • “Status” feed updating
    • Push Notifications
• Websockets
  • Designed to overcome many of the pitfalls/shortcomings described in RFC 6202
  • Standardized by IETF (Internet Engineering Task Force) in 2011
  • Can send and receive information (full-duplex pipe)
  • Protocol based on TCP
  • Uses HTTP only for initial handshake, while leveraging existing HTTP infrastructure
  • iOS Implementation
    • CFStreamCreatePairWithSocketToHost takes url, read and write stream
    • Cast read and write stream to NSInputStream and NSOutputStream, respectively
    • Set delegate for input and output streams
    • Schedule both in a run loop (Can do without but will block the execution of other code)
    • Open connection
    • Write code to handleEvents from the input stream
    • Implement message sending via the output stream
  • Server considerations
    • Not as easy to get started with as a generic web server
    • Buy one, borrow one or build one
  • Common uses
    • Chat
    • Player vs. Player games
    • Real time interactions
• Popular Abstractions/Frameworks
  • TRVSEventSource from Travis Jeffery
  • SignalR from Microsoft

At-a-glance Comparison

	Websockets	SSE	Long Polling
Client Performance	Best	Best	Worst
Server Performance	Best	Worst	Worst
Complexity	Highest	Lowest	Mid
When to Use	2-way messaging	Push to Client	Just getting started

Picks

Darryl

• Proportional Spacing with Auto Layout

John

• Google Cloud Vision API Detects types of images, landmarks, recognizes text, does image sentiment analysis and can even detect “inappropriate content”
• Agile and Beyond 2016 May 5-6 in Ypsilanti, MI

Alternative show title suggestions

• Uncanny valley
• The cooker's always on
• Canonical Framing Technique

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