Some network operations breaks on timeout

[atauenis]

Some operations related to download something from remote servers are hanging and falling off due to timeout.

Examples:

1. Image converting.
   1.1. Browser trying to download a webm picture (and a webm->gif rule is present in webone.conf).
   1.2. WebOne returns a 302 to converter.
   1.3. Browser opening converter page.
   1.4. Starting the converter.
   1.5. Converter attempts to download source file....
   1.6. After some time download fails. The error is Timeout.
   1.7. But in 80% of attempts the file gets successfully downloaded in adequate time and then converted without problems.
2. Simply opening a page.
   2.1 Browser trying to download a page via proxy (GET http://... HTTP/1.0.....).
   2.1 WebOne is downloading the page...
   2.2. After few minutes network stack stops wait, and returning to WebOne a Timeout error.
   2.2.1 But most of attempts have no problems here. And the original page correctly loaded by WebOne and then gets processed okay.

This appear at least on both Win7 SP1 and Win10 1903. Different hardware, antiviruses, ISPs, LANs, etc... The common here is using default Windows Firewall.

Any ideas why?

• Incorrect .NET network stack usage?
• Windows Defender-Firewall machinations?

[atauenis]

Related discussion (in Russian): https://qna.habr.com/q/696033

[atauenis]

Probably solved. At least my modest testing wasn't detected any Timeouts.

This was caused by excess of limit of possible network connections. Rewritten HTTP downloader, now network resources are freeing and the bug does not appear in test environment.