The default port number used by PPtp, the first layer tunneling protocol of VPN (Virtual Private Network), is TCP 1723, which is a standard, that is to say, this port number is used not only by the VPN service provided by Microsoft Windows Server, but also by other systems or hardware VPNs.

However, if you use the VPN server built by Windows Server's own Routing and Remote Access (RRAS), you can modify this port number through the registry to hide this service. But the VPN client to be used is still the VPN connection that comes with Windows.