why does my Com port transmission stop in windows 10?

Question

Hi, I hope someone here can help me.

I work for a company that uses a RS485 to transfer a program to a circuit board.

We have found since swapping most of our machines to Windows 10 that we can no longer transmit these programs.

I have installed a port sniffing tool and found that when the program sends an exclamation mark (!) the port will stop transmitting.

This problem is not found in windows 8.1 or earlier.

We have also found that if we run the software inside a virtual PC the port still works, so its not a hardware issue.

I have also tried a Windows 11 machine and found the same problem exists.

The software was originally written for Windows XP is no longer being updated by the manufacturer, but they also have had no luck in finding a solution.

Picture attached, the left side is a successful transmission in Windows 8.1 and the right is a failed transmission in Windows 10 using the same hardware and file.

Windows 8.1 was inside a virtual machine in the Windows 10 machine

Answer 1

Hi. Thank you for your question and reaching out. I’d be more than happy to help you with your query.

Make sure that you allowed the port through your firewall. Go to System and Security in the Control Panel, then select Windows Firewall. Go to the Advanced tab and then right-click on Inbound Rules in the left pane. Choose New Rule, enter the port, and then click Next. Choose the Protocol and Port Number, then click Next. Allow the connection and then click Next. Choose the network type, then Next, name the rule, and finally Complete.

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