The page https://koha-community.org/manual/latest/en/html/webservices.html#sru-server does not indicate - that the SRU feature is not working by default and must be activated by the administrator (with this procedure https://wiki.koha-community.org/wiki/Setting_up_the_Z39.50_and_SRU_Server ) - that the port 9999 is only an example and could be different in a specific installation