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
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John
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