Antivirus software blocks Server Side Events (EventSource)

[tomcatmwi]

Hi,

I'm trying to implement a Server Side Event connection between a Node.js backend and the frontend with EventSource.

It works perfectly... as long as I turn off my antivirus. As soon as it's on, it's silently blocking incoming responses.

It doesn't matter if I try it on localhost or my Heroku VM. It just doesn't work.

However, the example provided by W3Schools works:
https://www.w3schools.com/html/tryit.asp?filename=tryhtml5_sse

What's the magic? I've looked at the HTTP headers and replicated them... but to no avail.

I offered a bounty on Stack Overflow for a solution:

https://stackoverflow.com/questions/63716882/server-side-events-blocked-by-antivirus