Call func for each client managed by this.
The result value of func determines what happens to the client. func will be called with
this locked so no further actions on this can be performed from
func.
If func returns REMOVE, the client will be removed
from this.
If func returns KEEP, the client will remain in
this.
If func returns REF, the client will remain in
this but will also be added with an additional ref to the result List of this
function..
When func is null, REF
will be assumed for each client.
| this |
a Server |
| func |
a callback |
| user_data |
user data passed to |
|
a List with all clients for which |