Issue Unstable FTP connect

[Erwan]

Server operating system version

AlmaLinux 9.4

Plesk version and microupdate number

18.0.65

Hello,

On several Plesk servers I regularly have problems using the PHP ftp_connect() function.
For example, a task executed every hour to connect to FTP access will have the following error 1 to 2x per day, not always at the same time:

PHP Warning: ftp_connect(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /var/www/vhosts...

This looks like a failed DNS resolution from time to time but it's impossible to know how to resolve this.
An idea.
Thank you.

 

[WebHostingAce]

Since you mentioned that this issue occurs intermittently, have you considered scenarios such as the server attempting to resolve the hostname via IPv6, while your FTP server may not support IPv6?

 

[Erwan]

Note. Do you know of a way to ensure this? or to force an IPv4 resolution?

 

[WebHostingAce]

Is this a custom PHP script?

 

[Erwan]

Yes.

 

[WebHostingAce]

Sorry, as you can understand, it would be a bit difficult to comment on this without seeing the custom PHP script.

Also, have you checked the FTP log on the remote server when this issue occurs?

 

[Erwan]

$ftp_host ="mydomain.com";
$conn_id = ftp_connect($ftp_host,21);

I tried to force IPv4 resolution with this:
$ipv4_address = gethostbyname($ftp_host); // Resolve IPv4
$conn_id = ftp_connect($ipv4_address,21);
I'll see if that fixes the problem...