Is there a way to monitor a serial port without occupy it

[jiangliang]

Hello, I have a question about monitor com port data, I have to display some information in labview GUI, I already get the communication protocol from the vendor, but if I access the com port, the vendor's app won't be able to start, since I have occupied the com port.

Is it possible to only check the com port data but not really occupy it? I don't need to send any data, only recive and display.

Thanks!

[GerdW]

Hi jiang,

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@jiangliang wrote:

Is it possible to only check the com port data but not really occupy it? I don't need to send any data, only recive and display.

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No, you can only assign a COM port to a single application.

Why do you need the vendor app at all when you are in control of the device communication?

[Yamaeda]

Can't you communicate with their driver? Otherwise i guess you could use a sniffer like Wireshark, but it sounds messy.

[UliB · Accepted solution]

You could try software like:

- https://www.serial-port-splitter.com/ 

- https://freeserialportsplitter.com/ 

[jiangliang]

The control logic is kind of complex for me to reimplement, so I have to leave the vendor's app to do it's job.

I eventually add an additional com port hardware and wire the RXD to it, read and display data from this com port. Not a perfect solution, but I can live with that.

[pincpanter]

There are Serial Protocol Analyzer applications. Some are even free, although often with limited capabilities.

Just as an example: https://freeserialanalyzer.com/

[BertMcMahan]

I really like "Device Monitoring Studio" (https://hhdsoftware.com/device-monitoring-studio). It's not free but it's very useful. That one lets you sniff active serial ports (show all data transferred) without interfering with it, which is super useful for debugging. You could also use the virtual splitter option, but for just looking at data I think a "sniffer" is the way to go.

[ThomasHenkel]

As an addition: a simple free variant of monitoring a COM interface is Docklight with com0com.

[Kyle97330]

Something else to consider in some situations would be getting a hardware tap:

Get one or two of these and you can use a PC to read the lines completely independently of the sender and receiver.  Can be handy if neither end of the communications is something you can run a program on (or install serial port emulation on).

[weerapong]

Hi All

Thank you very much.

That is what I needed.

BR

Bee