SOLVED
Added
socket.io {"address": */*};Default "address:" **; that's is problem.
It's not an IPv6 address, it's a block of IPs in CIDR notation:
https://www.ultratools.com/tools/ipv6CIDRToRangeResult?ipAddress=2001%3Adb8%3A%3A%2F64
Blocking a single IPv6 address isn't very effective.
https://community.nodebb.org/topic/11127/block-ipv6 I was trying to blacklist a block of IPv6 adresses (an IPv6 prefix actually) but that results in a 'rule is invalid' message when I try to enter something like: 2001:db8::/64 This with ...
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