server closes connection before transmitting data on Android 8.1

[mnalis]

When I try to tranfer data with "Share via HTTP", I cannot establish HTTP connection.
So it looks like this:

$ wget http://192.168.9.111:9999/
--2019-01-11 19:37:43--  http://192.168.9.111:9999/
Connecting to 192.168.9.111:9999... connected.
HTTP request sent, awaiting response... Read error (Connection reset by peer) in headers.
Retrying.

and this:

$ telnet 192.168.9.111 9999
Trying 192.168.9.111...
Connected to 192.168.9.111.
Escape character is '^]'.
Connection closed by foreign host.

No file transfer takes place, of course. So the mobile phone accepts connection, and then terminates it.
I'm attaching tcpdump PCAP file for even more details.

That happens on Redmi note 6 pro, running android 8.1.0 (MIUI 10.0.5.0) with latest "Share via HTTP" v.2.0.8 from f-droid. I've disabled power saving for the app and permissions look ok.

When I try the same thing on same network using LG G3 running LineageOS 14.1 (Android 7.1.2), it works just fine. Any idea what may be the problem?