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Re: One CFSocketStream opening multiple sockets (and failing)
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Re: One CFSocketStream opening multiple sockets (and failing)


  • Subject: Re: One CFSocketStream opening multiple sockets (and failing)
  • From: "Quinn \"The Eskimo!\"" <email@hidden>
  • Date: Mon, 07 Sep 2015 11:15:42 +0100

On 3 Sep 2015, at 20:38, Jens Alfke <email@hidden> wrote:

> What I’m seeing is that, although I only open one client connection, i.e. one call to CFStreamCreatePairWithSocketToHost, the server receives up to _three_ incoming TCP connections.

I don't have time to look at this issue as a whole, but I can offer insight into the above.  Since 10.7 (and iOS 5?) the system has contained small connect-by-name code that:

1. resolves the name to a set of addresses

2. uses the routing table to work out how to prioritise those addresses

3. starts a connection to the best address

4. if that takes too long, starts a connection to other addresses

Normally this doesn't increase server load because step 3 connects before step 4 kicks in.

The gist of this was explained right here on MacNetworkProg.

<http://lists.apple.com/archives/ipv6-dev/2011/Jul/msg00009.html>

This algorithm has evolved over time and I'm not intimately familiar with the recent changes but its existence does explain part of this puzzle.

Share and Enjoy
--
Quinn "The Eskimo!"                    <http://www.apple.com/developer/>
Apple Developer Relations, Developer Technical Support, Core OS/Hardware



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  • Follow-Ups:
    • Re: One CFSocketStream opening multiple sockets (and failing)
      • From: Jens Alfke <email@hidden>
    • Re: One CFSocketStream opening multiple sockets (and failing)
      • From: "Quinn \"The Eskimo!\"" <email@hidden>
References: 
 >One CFSocketStream opening multiple sockets (and failing) (From: Jens Alfke <email@hidden>)

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