You can connect clients directly to your ESXi network instead of using vCenter Server.
Networks configured without vCenter Server receive communications through the vSphere Client, one of the vSphere command-line interfaces, the vSphere Web Services SDK, or third-party clients. For the most part, the firewall needs are the same as when a vCenter Server is present, but several key differences exist.
As you would for configurations that include vCenter Server, be sure a firewall is present to protect your ESXi layer or, depending on your configuration, your clients and ESXi layer. This firewall provides basic protection for your network.
Licensing in this type of configuration is part of the ESXi package that you install on each of the hosts. Because licensing is resident to the server, a separate license server is not required. This eliminates the need for a firewall between the license server and the ESXi network.
You can configure firewall ports using ESXCLI, using the vSphere Client, or using firewall rules. See ESXi Firewall Configuration.