There are many CLI options for this. And many ways to skin this cat. But below should get you pointed in the right direction.
CIFS for instance. For the NFS and CIFS options, make sure you turn them back off after you are done using the commands to see clients as they do add minor overhead to your filer while collecting data.
option cifs.per_client_stats.enable on
and you can run cifs top to see clients
You may also be able to 'manage' your filer from a windows system to view connected clients via CIFS as well.
option nfs.per_client_stats.enable on
then run vfiler run vfiler0 nfsstat -z to clear your table, then vfiler run vfiler0 nfsstat -l to list NFS clients (of course your vfiler may not be 0)
for SAN, check out your iscsi and fcp commands below