i want to install open-xchange on my server. And now i am at the point to register the database

$ /opt/open-xchange/sbin/registerserver -n oxserver -A oxadminmaster -P admin_master_password

but it doesn't work. I always get these massage:

server could not be registered:
Error: Connection refused to host: localhost; nested exception is:
java.net.ConnectException: Connection refused

what can i do to fix it?