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Re: NSURLConnection weirdiness
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Re: NSURLConnection weirdiness


  • Subject: Re: NSURLConnection weirdiness
  • From: Jens Alfke <email@hidden>
  • Date: Sat, 29 May 2010 12:12:48 -0700

On May 29, 2010, at 11:53 AM, Nava Carmon wrote:

> When I initialize the NSURLConnection I define a timeout in my NSURLMutableRequest in order not to stuck the GUI and let the user to work with application. On timeout I get didFailWithError in NSURLConnectionDelegate and show a message that there was not response from the server and the user can continue working.

If you’re running the NSURLConnection asynchronously (which I think you are, since you use a delegate), you can already unblock the UI and let the user continue to work. That’s a better design than waiting until the connection finishes, especially in a mobile app. (For example, my Twitter client returns to the timeline as soon as I press the Post button, and sends the post to the Twitter servers in the background.)

> The matter is that the connection or underlying socket somehow is preserved and the connection with the server is not closed. So when I try to get another url from the same server I can't reach it since the server is still stuck with the previous problematic request!

Hm. It’s true that CFNetwork uses HTTP keep-alive mode, where it can reuse a socket for multiple requests. But I don’t think it’ll send a second request on the same socket until the previous one is complete. (I.e. I don’t believe it supports pipelining.) Instead it should be opening a new socket while the first one is busy, up to a max of I think 4 sockets per host.

I don’t know if there’s any way, using public API, to disable keep-alive. It’s possible using a lower-level API like CFStream would let you get around this. I would ask on the macnetworkprog list. (And make sure to mention that this is on iPhone, as the APIs aren’t exactly the same as on Mac.)

> Each time I need to get xml file I create another NSURLConnection. I read somewhere that it's not a good practice…

No, that’s fine. The API was designed so that one connection = one request; note that there’s no way to re-use a NSURLConnection object for a second request. Under the hood the CFNetwork framework will be as efficient as it can, by re-using sockets when possible.

—Jens

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  • Follow-Ups:
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References: 
 >NSURLConnection weirdiness (From: Nava Carmon <email@hidden>)
 >Re: NSURLConnection weirdiness (From: Jerry Krinock <email@hidden>)
 >Re: NSURLConnection weirdiness (From: Nava Carmon <email@hidden>)

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