Display error message when a serial com device disconnects from computer

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Hi guys

I'm making a WinForms application to access a serial port(I'm using a arduino nano)

It's just a user interface to change ports and set baud rates etc. I've been following youtube tutorials mostly and it's pretty much done.

But now, I would like to add a function where, a MessageBox appears when the serial com device disconnects from the computer. I'm guessing I am supposed to use a PinChanged event? How do I write it though?

Thanks for reading! Any response is appreciated!

What I have tried:

private void SerialPinChangedEventHandler(object sender, SerialPinChangedEventArgs e)
        {
            if (SerialPinChange)
            {
                MessageBox.Show("Hardware disconnected", "Serial Port interface", MessageBoxButtons.OK, MessageBoxIcon.Stop);
            }
        }

Posted 30-Sep-20 21:05pm

pogcat5000

Updated 30-Sep-20 21:32pm

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Sandeep Mewara · Answer 1 · 2020-09-30T21:23:00

You could use following two information:
SerialPort.PinChanged Event (System.IO.Ports) | Microsoft Docs[^]
SerialPinChange Enum (System.IO.Ports) | Microsoft Docs[^]

Similar question asked and answered: How to detect when hardware connected to serial com port is (disconnected)removed?[^].

A diffeent approach discussed here[^] where you can use SerialPort.GetPortNames() only return the ports that are available. Then make the deduction.

OriginalGriff · Answer 2 · 2020-09-30T21:32:00

You can't definitely detect physical disconnection, unless some signal is held high by the hardware at the other end of the wire - and most wires don't do that, they use "local loopback" by physically wiring RTS to CTS at the plug for example, if they even do that - many serial interfaces literally just have physical wires connected to pins 2, 3, and 5 (TD, RD, and ground) as the minimum connection required.

Start by looking at your actual physical connections: if you are connected via USB, you can tell when the plug is undone from your end, but once it gets to actual RS232 / RS485 wiring you need to know exactly what is wired to what from end to end.

The easier way is probably to put a "watchdog timer" in the software to detect when there has been no communications between them for a period of time, and try to query the remote device to see if it responds. (Most protocols include a "are you alive?" callback request for this purpose, but you'll have to look at the comms manual for the actual device to check)

Display error message when a serial com device disconnects from computer

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