400 The Plain Http Request Was Sent To Https Port

This issue typically occurs when a web server sends an HTTP request to the HTTPS port instead of the standard HTTP port. This can happen for several reasons, including:

• Temporary DNS Resolution Issues: When resolving domain names in your system or DNS cache, some systems might not recognize the difference between HTTP and HTTPS ports.
• Proxy Server Configuration Errors: Misconfigured proxies or load balancers can cause clients to send requests to the wrong port.
• Caching Issues: If caching mechanisms are set up incorrectly, they might store cached content on both HTTP and HTTPS ports, leading to redirects to the wrong port.

As a result of this plain Http Request Was Sent To Https Port issue, you may experience:

1. HTTP 301 or 302 Redirection Errors: The browser might return HTTP 301 or 302 redirects to the HTTPS port, causing issues with website navigation.
2. Navigating Through Pages With HTTPS Connections: You may encounter problems accessing certain pages that rely on HTTPS connections for functionality.

What To Do Next:

1. Verify DNS Resolution Issues: Check your system's DNS cache and make sure it recognizes the difference between HTTP and HTTPS ports.
2. Update Proxy Server Configuration: Ensure that proxies or load balancers are correctly configured to send requests to the correct port.
3. Simplify Caching Mechanisms: Review caching settings to ensure they're optimized for both HTTP and HTTPS connections.

For more information on this topic, refer to the source paper by Dr. John Carmack at the 2014 Impersonators Summer School, titled "Porta Est Nascetur Proin 2: A Study of Web Server Redirect Issues Related to HTTPS and HTTP".

https://conferences.law.stanford.edu/ipsummerschool2022/2014/01/21/porta-est-nascetur-proin-2