Serial COM Ports That Do Not Exist in The Computer Shows up in NI MAX With Exclamation Mark

Updated Aug 12, 2022

Issue Details

I am monitoring a PXI system (Remote Desktop) from my local computer using Remote Desktop Connection (RDC). I see few additional COM ports with exclamation mark in the NI Measurement and Automation Explorer (NI MAX) of the remote desktop that doesn't exist in the system and also they do not show up in the Windows Device Manager.

How to remove these non-existent (ghost) COM ports with the exclamation mark?

Solution

When you are accessing or monitoring a remote desktop from local computer, please check if the additional COM ports that are displayed with exclamation mark in NI MAX of the remote desktop are available/present in the local computer.

If yes, then the COM ports are forwarded from local computer to the remote desktop due to port forwarding via Remote Desktop Protocol (RDP). To resolve the issue, disable COM port forwarding which doesn't forward the Serial COM ports from local computer to the remote desktop and removes the additional COM ports with the exclamation mark.
 

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