SyncML via RPC.php

Hello,

when I try to access my Groupware Install via Syncml in linux terminal via

syncml-ds-tool --http-client “http://XXX.com/egroupware/rpc.php” --slow-sync text/x-vcard Contacts /tmp/syncml/webcontacts --username XXX --password XXX

always

** Message: ERROR: The alert response signals an error - 401.

is returned. Does anyone have an idea?