[jetty-users] File upload fails on live system, works on development sys

[John English <john.foreign@xxxxxxxxx>]

Hi folks,
I am having a strange problem with file uploads. Fortunately it's 
something that only the sysadmin has access to and is used very rarely, 
so the user base is not affected. The site uses HTTPS exclusively.

On the live system, trying to upload a file from Firefox gives this error:

Secure Connection Failed

An error occurred during a connection to mysite.com. 
PR_CONNECT_ABORTED_ERROR

The page you are trying to view cannot be shown because the authenticity 
of the received data could not be verified.

Trying it from Chrome gives this:

This site can’t be reached
The webpage at mysite.com/foo might be temporarily down or it may have 
moved permanently to a new web address.
ERR_CONNECTION_ABORTED

The fact that it fails on multiple browsers tells me it's a config error 
of some sort.

When I try it on my development rig, it works perfectly. The only 
difference is that the development rig runs on Windows 10 using Java 
1.8.0_172, the live system is Ubuntu 20.04 running Java 1.8.0_251 (both 
Javas are the Oracle versions). I'm using Jetty 9.4.39. The code uses 
javax.servlet.http.Part, and is pretty banal:

        Part part = request.getPart(paramName);
        ObjectInputStream stream =
              new ObjectInputStream(part.getInputStream());
        FileContent data = (FileContent)stream.readObject();

ON the live system, the request log shows lines like this:

 - - [20/May/2021:17:19:32 +0000] "POST /foo HTTP/1.1" 302 0

with no source IP. And as I understand things, POST requests shouldn't 
produce 302 responses.

Does anyone have any idea what might be going on here?
--
John English