Check if a port is blocked with socat

- How to check if a port is blocked with socat? - How to check with IPv6? I heard a saying that machines behind NAT can still be directly connected via IPv6, is that true? Anyway, say I have a machine behind very complicated setup, and I want to verify if a certain port can be reached, by either IPv4 or IPv6, how to do that with socat? Basically I need to start socat on the machine to listen, then try to conect to it via socat from other machines. I've read https://copyconstruct.medium.com/socat-29453e9fc8a6 , and found it a bit complicated, but I cannot just use netcat because my netcat version does not support IPv6, as per https://unix.stackexchange.com/questions/457670/netcat-how-to-listen-on-a-tcp-port-using-ipv6-address .