Getting all users in Moodle using web services

I am developing a Java client to interact with Moodle. I want all users to be logged into the Moodle installation.

I found a webservice function called core_user_get_users

that returns a list with users.

When I call the service without any parameters, I get an exception response invalid parameter

.

When I add criteria ( criteria[0][key]=id&criteria[0][value]=some_id

) parameter , it returns one user with that specific id

.

I can't find what criteria to pass to the function to get the entire list with registered users.