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Editorial Team
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Asked: 2026-05-13T07:43:58+00:00

Here’s what I’ve done: I wrote a minimal web server (using Qt, but I

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Here’s what I’ve done:

  • I wrote a minimal web server (using Qt, but I don’t think it’s relevant here).
  • I’m running it on a legal Windows 7 32-bit.

The problem:

  • If I make a request with Firefox, IE, Chrome or Safari it takes takes about one second before my server sees that there is a new connection to be accepted.

Clues:

  • Using other clients (wget, own test client that just opens a socket) than Firefox, IE, Chrome, Safari seeing the new connection is matter of milliseconds.
  • I installed Apache and tried the clients mentioned above. Serving the request takes ~50ms as expected.
  • The problem isn’t reproducible when running Windows XP (or compiling and running the same code under Linux)
  • The problem seems to present itself only when connecting to localhost. A friend connected over the Internet and serving the connection was a matter of milliseconds.
  • Running the server in different ports has no effect on the 1 second latency

Here’s what I’ve tried without luck:

  • Stopped the Windows Defender service
  • Stopped the Windows Firewall service

Any ideas? Is this some clever ‘security feature’ in Windows 7? Why isn’t Apache affected? Why are only the browsers affected?

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1 Answer

  1. Editorial Team

    If you’re saying “localhost” instead of “127.0.0.1”, you’re forcing a name lookup before the actual connection attempt, adding delay.

    In addition, some browsers, like Firefox 3.5+, don’t use the operating system’s DNS lookup mechanism, which is why it can have different performance than, say, wget.

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