Correct way to end serial port base stream reading

I've built a serial logger in c# using the solution from Ben Voigt

https://www.sparxeng.com/blog/software/must-use-net-system-io-ports-serialport

byte[] buffer = new byte[blockLimit];
Action kickoffRead = null;
kickoffRead = delegate {
    port.BaseStream.BeginRead(buffer, 0, buffer.Length, delegate (IAsyncResult ar) {
        try {
            int actualLength = port.BaseStream.EndRead(ar);
            byte[] received = new byte[actualLength];
            Buffer.BlockCopy(buffer, 0, received, 0, actualLength);
            raiseAppSerialDataEvent(received);
        }
        catch (IOException exc) {
            handleAppSerialError(exc);
        }
        kickoffRead();
    }, null);
};
kickoffRead();

All other methods I tried failed in one way or another (Ben Voigt explains extensively why on his excellent page). Now I'm only left with two questions:

1). How do I gracefully stop listening to the serial port? If I close the comport it will raise a nasty exception.

2). Is there an elegant way to raise an event if there is no data recieved for a certain time?