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After upgrading to .NET Framework 3.5, I can't set 80 as a HTTPS port in IIS6. Only when I uninstalled .NET Framework 3.5, IIS accepts 80 as a HTTPS port again and operate normally.

The question is whether this behaviour is by design or a bug results from unexpected interaction between IIS and .NET Framework 3.5.

To my understanding, Dot Net Framework should be web server agnostic and IIS should be software framework agnostic. Thus, if this behavior is indeed a design choice, why it did not show up in early versions of Dot Net Framework, e,g. 1.1 2.0?

Reproduction Steps: 1. Set 80 as a HTTPS port in IIS6

  1. Install .Net framework 3.5

  2. run "inetmgr", it appears that website is stopped.

  3. Remove port 80 from https configuration or uninstall framework 3.5, website is able to start again

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Couple of comments:

  • You are correct, .NET and IIS are separate and they should not depend or conflict with each other.

  • If you set HTTPS on port 80, this will break the majority of web browsers. HTTPS should be on 443. If anyone would go to HTTPS://; it would not work; likewise if they went to HTTP:// it would not work either. Only if they went to HTTPS:// would it work. Therefore, it could be by design choice that this configuration is rejected.

  • Did you disable HTTP on port 80? If you tried to enable HTTPS on port 80, before disabling HTTP, then this would be a port conflict and could be why your server doesn't start. It could just be a coincidence that it happened when you upgraded .NET.

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