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Ralph Scharping
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Accessing virtual COM Ports in RDP 2019

Good morning experts,

I am running a box pretty much standalone on Windows Server 2019 Standard.  There are several USB devices performing medical examinations connected.  Two out of these use virtual COM ports "under the hood".  
I can use both interfaces as Administrator, but not as User with limited rights.  

Has anything changed in this regard?  So far using Server 2016 and before I never ran into trouble.

Just to clarify:  This is NOT a pass-through-question.  The devices are connected directly to the hardware running Server 2019.

Windows Server 2019Windows OS

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8/22/2022 - Mon

When accessing as auser, you get access related error or port in use?
Is there an application/service that captures/interfaces through which you can interact?
Ralph Scharping

The message depends on the application.  The medical Applications just say they can't connect.  One has a test tool, and that sais the port is in use.  I really don't know.

The interfaces are listed in hardware components and I can see that they accepted the correct drivers.


IN RDP are you sure when you try that you are the sole person using the port?
There is/was a software comm port that could facilitate function allowing multiple application to access a single comm port though that dealt with simply abserving data flow for items such a GPS feed..

Does the vendor indicate that your setup is supoorted or it is available for such a deployment?
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Ralph Scharping

Yes, therer are only five ThinClients and I am the only person here.  No matter which client I use:  If I am admin it works, if I am not, it does not.
The vendors are unable to understand the question much less answer it.  I am sure it is not supported as such, but it worked under the previous setup using Serve 2008 R2.

Is there a difference in the handling of COM-ports in 2019 vs. 2016?

I do not know as the use is highly customized.
Checking whether the manner in which the USB to comm port adapter deals with is it accessible to regular users.

Checking access rights to comm ports, if not mistaken, ms sysinternals has a comm port test, monitoring tool to see if it can be used to identify the reason user access to comm port runs into issues.

Look for comm port redirector, saw an example for a serial to tcp/ip ....

Ralph Scharping

These are VIRTUAL com ports - they are not actually RS232-interfaces, so a Serial to TCP/IP will not help.  It is a USB device that includes a USB to RS232 internal chip that accesses the older hardware that is used within the device.

I will try sysinternals, but it really is a access rights issue - either in file system or registry.  It is plain that everything works as user with administrative privileges but it does not when running the same thing as plain user.
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