From KB article: VMware KB: Required VMware vCenter Converter 4.x/5.x ports
Source: computer
Destination: ESX/ESXi
TCP Ports: 443, 902
Note: If the conversion destination is vCenter Server, only port 902 is required from the source to the ESX/ESXi hosts.
Then, since your destination is vCenter, you will need port 443 between source and vCenter and port 902 between source and ESXi host... about if need port 902 for all host, if your cluster have DRS enabled, disable DRS and point the P2V to a specific host and after the conversion finish, enable DRS again... if you don't want disable DRS, you will need open por 902 to all host in the cluster.