Warning when trying to subscribe a server to a multicast group

[gandalfitexpert]

Hello,

I am trying to bind a server to a multicast group, unfortunately, I get this warning :

PHP Warning: socket_set_option(): Unable to set socket option [92]: Protocol not available

I am using the copy/paste code from this documentation page :

https://openswoole.com/docs/modules/swoole-server-getSocket

namely, this line :

$ret = socket_set_option( $socket, IPPROTO_IP, MCAST_JOIN_GROUP, [ 'group' => '10.0.0.1', 'interface' => 'eth0' ] );
(assuming 10.0.0.1 is a muticast address)
I also tried using number '2' instead of IPPROTO_IP, unsuccessfully.

My environment is :
Windows 10
WSL 1
Ubuntu 22.04 LTS

BTW what about the port assignment, especially if you want a client to subscribe to the same group ?
Indeed a client would connect this way I guess :
$client->connect('10.0.0.1', 9905, 0.5)

So what about the port ? Do we care about it ?

Thanks for your help.

Regards