I have the same problem on FreeBSD 13.2. Same code/configuration listens on IPv4 on Ubuntu.

Did you solve it somehow in the end?

Try adding the explicit IP to listen on? Not sure what the defaults are.

E.g.:

  config :my_app, MyWeb.Endpoint,
    url: [host: host, port: 443, scheme: "https"],
    http: [
      ip: {0, 0, 0, 0},
      port: port
    ],

Managed to solve it. I’m in the process of migrating from Ubuntu Linux to FreeBSD and for some reason on Ubuntu Linux Phoenix did bind to the IPv4, but using the same code and configuration on FreeBSD did bind only on IPv6.

I tried all tricks on changing config/config.exs, config/prod.exs and config/prod.secret.exs, but it turned out that the problem was in the lib/my_app_web/endpoint.ex where in init function had the following line:

{:ok, Keyword.put(config, :http, [:inet6, port: port])}

Changing it to:

{:ok, Keyword.put(config, :http, [:inet, port: port])}

I’m pretty sure that this line has been on inet6 for the entire time of the project and it was generated by phx.new at the time of project creation. Just bear in mind that this is a legacy Phoenix application running version 1.5.1 and might not have the same generated file when creating a new Phoenix application today.

On Linux, by default, an “inet6” socket also accepts IPv4 (you can disable that with the sysctl option net.ipv6.bindv6only or by adding {ipv6_v6only: true} to your socket options). On FreeBSD, it is not the case by default. You can enable a similar behaviour by adding ipv6_ipv4mapping=YES in /etc/rc.conf. See rc.conf(5)

I’m on 14.1 and can’t get it to bind to tcp4.

$ doas netstat -an | grep LISTEN
tcp6 0 0 *.4000 . LISTEN

I have also set ipv4 mapping in rc.conf.

rc.conf

ipv6_ipv4mapping=“YES”

$ uname -a
FreeBSD learning01 14.1-RELEASE-p5 FreeBSD 14.1-RELEASE-p5 GENERIC amd64

Any ideas?

This problem even persists on FreeBSD 14 when applying the changes in endpoint.ex as described above by me?