Reproduction test case for https://github.com/NeuronRobotics/nrjavaserial/issues/197.

DisconnectTest.java

import java.io.IOException;
import java.io.InputStream;
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;

public class DisconnectTest
{
    private static final int SLEEP_AFTER_DISCONNECT = 2_000;

    public static void main(String[] args) throws Exception
    {
        String portName = args[0];
        // The bug is equally-reproducible with the NRSerialPort wrapper. To
        // try, uncomment this, comment out the `CommPortIdentifier` lines...
//      NRSerialPort port = new NRSerialPort(portName, 115200);
        CommPortIdentifier identifier = CommPortIdentifier.getPortIdentifier(portName);
        SerialPort port = identifier.open("disconnect-test", 0);
        // ...uncomment this...
//      port.connect();
        InputStream in = port.getInputStream();
        System.out.printf(
            "Opened port %s and beginning to read. Trigger a " +
            "hardware error now.\n",
            portName);

        try
        {
            while (true)
            {
                in.available();
            }
        }
        catch (IOException e)
        {
            System.err.printf("Caught an exception: %s\n", e.getMessage());
        }

        System.out.printf("Going to disconnect the port...\n");
        // ...uncomment this, and comment out the call to `port.close()`.
//      port.disconnect();
        port.close();
        System.out.printf(
            "Disconnected. Now going to sleep for %.1fs to give the monitor " +
            "thread a chance to SIGSEGV.\n",
            SLEEP_AFTER_DISCONNECT / 1_000.0);
        
        try
        {
            Thread.sleep(SLEEP_AFTER_DISCONNECT);
        }
        catch (InterruptedException e)
        {
            System.err.printf("Sleep was interrupted. Test abandoned.\n");
            System.exit(1);
        }

        System.out.printf(
            "If you're seeing this, that means the monitor thread didn't " +
            "segfault, and bug reproduction has failed.\n");
    }
}