Thank you for your suggestion, Joakim, I didn't think about it.
So I have added the remote port to the log (and also upgraded to Jetty 9.4.37.v20210219)
and yes - the ports are different (please see the log below)... but how can a single user have so many connections (over a dozen) open to my game which requires a single connection only?
What is the explanation? Some buggy browser (my players are from Russia) or too many tabs?
qtp100555887-17: onWebSocketClose: hostname=77.111.247.123 port=13533 mUid=18555 statusCode=1006 reason=Disconnected
qtp100555887-34: onWebSocketClose: hostname=77.111.247.123 port=55271 mUid=18555 statusCode=1006 reason=Disconnected
qtp100555887-71: onWebSocketClose: hostname=77.111.247.123 port=33979 mUid=18555 statusCode=1006 reason=Disconnected
qtp100555887-17: onWebSocketClose: hostname=77.111.247.123 port=58969 mUid=0 statusCode=1006 reason=Disconnected
qtp100555887-54: onWebSocketClose: hostname=77.111.247.123 port=56049 mUid=18555 statusCode=1006 reason=Disconnected
qtp100555887-34: onWebSocketClose: hostname=77.111.247.123 port=37309 mUid=0 statusCode=1006 reason=Disconnected
qtp100555887-54: onWebSocketClose: hostname=77.111.247.123 port=52163 mUid=18555 statusCode=1006 reason=Disconnected
qtp100555887-17: onWebSocketClose: hostname=77.111.247.123 port=59447 mUid=0 statusCode=1006 reason=Disconnected
qtp100555887-66: onWebSocketClose: hostname=77.111.247.123 port=40691 mUid=0 statusCode=1006 reason=Disconnected
qtp100555887-71: onWebSocketClose: hostname=77.111.247.123 port=42557 mUid=18555 statusCode=1006 reason=Disconnected
qtp100555887-71: onWebSocketClose: hostname=77.111.247.123 port=57649 mUid=18555 statusCode=1006 reason=Disconnected
qtp100555887-71: onWebSocketClose: hostname=77.111.247.123 port=15239 mUid=18555 statusCode=1006 reason=Disconnected