I was reviewing the VMware KB article which describes all of the ports and protocols the various pieces of vSphere uses. The table for ESXi seems to indicate that the ESXi host never initiates communication with the vCenter server. vCenter server is always the entity which reaches out to touch the ESXi host, be it over 443, 902, 903, etc. One of my co-workers brought up the issue of the heartbeat between ESXi and vCenter. Does ESXi initiate the heartbeat or does vCenter poll the ESXi hosts?

We are putting together a detailed visio diagram of all communications, so we need to get directionality right. We found a detailed diagram on the web which drew out all the communications and it shows bi-directionality between ESXi and vCenter, which condradicts the official port table in the KB article.