/usr/local/ispconfig/server/scripts/ispconfig_update.php
Update script hangs in most cases in ipv6-enabled systems, trying to retrieve version info file.
Server OS: Ubuntu 16 & 18
proposed fix
Use curl.
/usr/local/ispconfig/server/scripts/ispconfig_update.php
Replace line 94
-- $new_version = @file_get_contents('http://www.ispconfig.org/downloads/ispconfig3_version.txt') or die('Unable to retrieve version file.');
with
++ $ch = curl_init('http://www.ispconfig.org/downloads/ispconfig3_version.txt');
++ curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
++ new_version = curl_exec(
ch) or die('Unable to retrieve version file.');
Edited by MikeG