Been digging around as I've been wanting a suitable CIM client to test connections to our ESXi 5.1 hosts to enumerate WBEM data. Came across this info from VMware that might also help with troubleshooting CIM server issues:
For instance, the above doc notes that if your host is in lockdown mode, you can only connect to the CIM server using an authentication ticket obtained from vCenter. You cannot directly authenticate via ID/password.
This doc shows default ports/protcols open for CIM server: