Hello
I assume you do Linux P2V because you mention 'helper'. The process for Linux and Windows P2V is very different hence the limitations too are different.
You should be able to do the conversion (if it was Windows, you probably shouldn't). The network connectivity you need is from the helper (i.e. from the VM network the helper will be on) to the source machine for SSH (port 22 by default). You can verify the connectivity by trying to SSH from another VM in the same network.
HTH
Plamen
P.S I don't know what Abhilash means by suggesting to remove the ESX from the VC, this is irrelevant IMO.