ESP8266 HTTP server returns err_connection_reset while WebREPL works fine

[Lenergy1982]

Please help!!
I'm using the code example for a simple HTTP server, located here: https://docs.micropython.org/en/latest/esp8266/tutorial/network_tcp.html to publish information, which I get from a sensor.
WIFI and WebREPL are involved. The board is ESP8266 NodeMCU v3.

The problem is: after a period of time (maybe 1 hour) the HTTP server stops functioning - Chrome shoes err_connection_reset message, while WebREPL link on 8266 port works fine.

What may be the cause of such behavior? Tried to disable gc with gc.disable(), but it didn't help. Setting sleep mode to SLEEP_NONE also didn't work.

[Lenergy1982]

Well, understood why this happens after an hour after publishing the question, although couldn't solve the problem for 3 days before.
The board was visible from outside the local network and it stopped working after connections from unknown IP addresses (bots?).
So I think I need some kind of a filter..