Link IPv4 and IPv6 into a single instance on the server (connection server <-> client) about openvpn HOT 6 CLOSED

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But proto udp6 not limit connection in IPv6 ?

With dual-socket can I have the same IPv4 and IPv6 instance? How do I create a dual-stack socket?

OS: Debian
OpenVPN version: 2.4

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Right, using proto udp6 by example without directive local the server listen up in " :: " only.

The use of local is valid only once and as defined by udp6 an IPv4 in local is not accepted, so far so good, it's expected. IPv4 and IPv6 traffic between the ends works, but I want an instance on the server that allows the client to connect to my IPv4 or my IPv6 explicitly in directive remote ...

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If you want the server side to explicitly bind to a specific IPv4 or
IPv6 address, then you need to run two instances today.

Normally this is only needed if you have multiple IPv4 addresses, and
want OpenVPN on only one of them - but this is a known shortcoming
(you can not have "I have 3 IPv4 addresses and want OpenVPN only to
listen on 2 of them" either) - as soon as you put local in the config,
it's "one address, one protocol" only.

Understood

[ .... ] What is in the client config does not need to match the "local" part of the server
config (unless you use old-style --secret without --float).

In client is using float conf

On FreeBSD, you can see "46" in the first column:

FreeBSD$ netstat -an |grep 51194
tcp46      0      0 *.51194                *.*                    LISTEN
udp46      0      0 *.51194                *.*

but Linux is not showing it

Linux$  ss -an |grep 51194
udp     UNCONN   0        0                                                   *:51194                                                 *:*
tcp     LISTEN   0        32                                                  *:51194                                                 *:*

In my case, using proto udp6 in server without local, with IPv4 and IPv6 settings, i have output ss -an | grep 1194:

udp   UNCONN    0      0                                    *:1194                         *:*

In netstat -anp | grep 1194

udp6       0      0       :::1194                 :::*                                11210/openvpn

In client:

proto udp
remote IPv4
remote IPv6

Really in netstat and ss appears to listen only on IPv6.
Now, with the confs above my client connect in both the protocols, very good. It was what I needed.

How is this possible? is it the socket management that allows this?

Very thanks by explanation @cron2

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