Question: how to get wwn number in esxi?
Answer: Connect to ESXi shell either via putty/SSH or DCUI (Direct Console User Interface) / server console.
Run 'ls /proc/scsi/' and check the folder names: ... 
Look for a folder like 'qla2xxx' – QLogic HBA, 'lpfc820' – Emulex HBA, 'bnx2i” – Brocade HBA;
Run 'ls /proc/scsi/qla2xxx'.