I hope this will not be any flame... but I hardly can believe that in a
normal linux/bsd distribution there isn't any tool for redirecting
stdin/stdout to a (new) tcp/udp connection. I think that
file-descriptor-fans will know something like that...

The most similar program I found is 'netcat', but in all the versions
I've seen, it makes SO_LINGER with linger active, with a 0 seconds
timeout, making it unusable for a "close() after input EOT"-behaviour.
Moreover, netcat isn't a default as "ls" or "cat".

Am I missing something? Which is the program I'm expecting to find for
that redirection?

Thanks in advance!