Azure VMs - Allowing Communication on Selected Ports - Azure Blogger

RDP Different port

Faq / March 1, 2022

Port Number Value DialogFor a project I’m working on, we have an automated build server running CruiseControl.NET hosted in a virtual machine. We do the same thing for Subtext.

Some of you may have multiple virtual servers running on the same machine. Typically in such a setup (at least typically for me), each virtual server won’t have its own public IP Address, instead sharing the public IP of the host computer.

This makes it a tad bit difficult to manage the virtual servers since using Remote Desktop to connect to the public IP will connect to the host computer and not the virtual machine. The same thing applies to multiple real computers behind a firewall.

One solution (and the one I use) is set up each virtual server to run Terminal Services, but each one listens on a different port. Then set up port-forwarding on your firewall to forward requests for the respective ports to the correct virtual machine.

Configuring the Server

The setting for the Terminal Services port lives in the following registry key:

VelocIT Terminal Services Port Changer{.registry .smallnote}

Open up Regedit, find this key, and look for the the PortNumber value.

Double click on the PortNumber setting and enter in the port number you wish to use. Unless you think in hex (pat yourself on the back if you do), you might want to click on decimal before entering your new port number.

Or, you can use my creatively named application, which is available with source. This is a simple five minute application that does one thing and one thing only. It allows you to change the port number that Terminal Services listens on.

Remember, all the usual caveats apply about tinkering with the registry. You do so at your own risk.

Connecting via Remote Desktop to the non-standard Port

Now that you have the server all set up, you need to connect to it. This is pretty easy. Suppose you change the port for the virtual machine to listen in on port 3900. You simply append 3900 to the server name (or IP) when connecting via Remote Desktop.

Keep In Mind

Keep in mind that the user you attempt to connect with must have the logon interactively right as well as permissions to logon to the terminal services session. For more on that, check out this extremely helpful article with its trouble shooting section.