V0.3.4 | Serial port cannot open

[MLaudren]

When using either server or client, with version 0.3.4,
I have an error: 'Device 1': Failed to open serial port. Error code: 2

Tried with different adapter and port, and also running as admin, but could not get it to work

If I do the same with version 0.1.5, all is working great.
Likely the new Modbus library have issue ?, as explain here: #10 (comment)

[serhmarch]

Hello. Error code: 2 is the value returned by the standard WinAPI function GetLastError() and means ERROR_FILE_NOT_FOUND according to the Windows documentation.

As I see in Project window you're using RTU:COM34. COM34 doesn't look like a valid serial port number. I just repeated your settings in server v0.3.4 app on Windows and I got completely the same output that you have. And this is understandable because I really do not have serial port with the name COM34 in my list of serial ports.

Maybe you selected COM3 and then accidentally pressed 4 and thus got COM34?

[MLaudren]

Hi Serhii,

I am using a lots of serial cables/adapter, and as Windows assign them individually, this one got the com port number 34,
See in screenshot from Device manager.

Same adapter, using Com34 is working fine with older version as I said.

If you think of tests I can do to narrow the area/cause, let me know, and I'll do.

[serhmarch]

Its hard to say what is cause of the problem. This error can occur only as result of CreateFile standard WinAPI function execution:

            ...
            d->serialPort = CreateFileA(
                d->settings.portName.c_str(), // Port name
                GENERIC_READ | GENERIC_WRITE, // Read and write access
                0,                            // No sharing
                NULL,                         // No security attributes
                OPEN_EXISTING,                // Opens existing port
                0,                            // Disables overlapped I/O
                NULL                          // No template file
                );

            if (d->serialPortIsInvalid())
            {
                return d->setError(Status_BadSerialOpen, StringLiteral("Failed to open serial port. Error code: ") + toModbusString(GetLastError()));
            }
            ...

https://github.com/serhmarch/ModbusLib/blob/63b40ec78d7bc81d4fa02a45b27020ddf3585154/src/win/ModbusSerialPort_win.cpp#L77

It might have something to do with the input parameters of the function.
First, I need to expand the error message in the next release, and then you can take new screenshots to see what values are passed to the function.

[serhmarch]

Hello. Please try new v0.3.5 version. Lets see what it would be.

[MLaudren]

Hi @serhmarch ,
I've done some tests, but still not working.

Server still cannot open the port

Client same as server

I'll try to test more later.
I didn't saw any logs I can share.

[serhmarch]

Hello. This behavior is also possible if the string COM34 somehow contains non-ASCII characters (for example, in Cyrillic there are all three characters COM looks like the same as in Latin, but they have a different byte code). + in version 0.1.5 it was not possible to enter the port name manually, only to select from the drop-down list, in this and previous versions it is possible.

I realize that in this case it is unlikely, I just left it here as an option.

Then please specify the version of the operating system and hardware. When I'll have time, I will try to run it on different machines, maybe I can get the same result.

[MLaudren]

Hi @serhmarch ,

I'm running the application on Win 11 Pro (23H2)
As for the hardware, I have some FTDI base USB/RS485 adapter, B&B Electronics USOPTL4, and other 3rd party cables.