This KB article restates an item from the vCenter 5.5 Update 2 release notes:
Virtual machines with HTML 5 console in vSphere 5.5 open connections with http:// instead of https://
When the HTML 5 console is launched on a virtual machine, it uses connections like http:// and web sockets like ws:// instead of secure connections like https:// and wss://.
This release resolves the issue by launching the virtual machine console with secure connection over port 7343 instead of the connection over port 7331.
This was a welcome change, but it introduces a potential connectivity issue for those who don’t read the release notes!
Here is a link to the release notes: https://www.vmware.com/support/vsphere5/doc/vsphere-vcenter-server-55u2-release-notes.html#networkingissues
Here is the top level KB article for required TCP and UDP ports for vSphere products. Notice the left hand column where the version numbers are listed!
TCP and UDP Ports required to access VMware vCenter Server, VMware ESXi and ESX hosts, and other network components