Up to three ports may be used between the ESX host and the collector:
[*] Port 443 (TCP) - VI SDK
The VI SDK connection is HTTPS-based, and used for collecting Metrics and Events. If you are monitoring metrics and events through the VC server, you do not need to enable this between the collector and ESX host as well.
[*] Port 22 (TCP) - SSH
The SSH connection is used to monitor the filesystem space available on the Linux Console OS, if you have checked this option. This may also require configuring the account, as described in our FAQ: http://tinyurl.com/2k99e6
[*] Port 514 (UDP) - Syslog
The syslog connection allows the collector to receive messages written by the vmkernel or HP SIM agent to the syslog daemon. This was the primary means of monitoring ESX for hardware failures before we added CIM/SMASH support in version 4.5, and has become somewhat less important because hardware data can now be obtained through the VI SDK. The syslog daemon on the ESX host needs to be configured, as described in the 4.5.2 Administrator Guide or the 5.0.0 Operations Guide (Appendix E for OMW, or Appendix C for OMU).
The collector can be configured to work on non-standard ports, which may be necessary, depending on your firewall's configuration.