server socket receives 2 http requests when I send from chrome and receives one when I send from firefox

I had a similar issue with my node server. It is due to the following bug in Chrome. In summary, Chrome is sending a request for a favicon on every request. As, is likely, you aren't sending a favicon back, it requests one after every legitimate request.

Firefox, and most other browsers, also send out a request for a favicon when they first connect, but cache the result i.e. if there isn't a favicon returned first time, they don't keep trying - which is why you're only seeing a single request from Firefox. It seems Chrome is unfortunately a little too persistent with its favicon requestiness.

I am currently writing small async web server on Mono/.NET 4.0 and noticed the same thing. Chrome opens two TCP connection, but only one is used for communication. There is no data send using that socket. Even after you stop loading webpage from browser Chrome still keeps connection alive for quite some time.

I must agree with @RomanK, as it's probably for optimizations or it's a bug, but it's not for favicon as there is not data transfered throw that connection.

I had empty tcp packet sent by Chrome to my simple server before normal html GET query and /favicon after. Favicon wasn`t a problem but empty tcp was since my server was waiting either for data or for connection to be finished. It had no data and wouldn't release connection for 2 minutes. So thread was hanging for 2 minutes.

In related question I found a useful link saying it may be caused by "Predict network actions to improve page load performance" setting. I tried turning off prediction settings one by one and it worked. In chrome version 73.0.3683.86 (Official Build) (64-bit) this behavior was caused by chrome setting "Use a prediction service to load pages more quickly" turned on.

So just go to setting -> advanced -> privacy and security -> Use a prediction service to load pages more quickly and turn it OFF.