QWebSocket disconnects without any notice

[mmjvox]

QWebSocket disconnects randomly and dosen't emit any signal as disconnected or closed or...
only this error faces when going to send a message :

QAbstractSocket::RemoteHostClosedError

On server side (QWebSocket + QWebSocketServer) there isn't any close or disconnect signal or error.

This happens on average 50 times a day.

framework version for client:
Qt 5.12.9 - windows(msvc) and linux

framework version for server:
static build of Qt 5.12.9 on centos gcc7