COMM outputstream blocking forever

Question

I am writing an application that talks with a modem through an RS232 serial port using the COMM packet on Windows.
The problem is how to detect when the modem is not there for some reason. I discovered that the outputStream.write(...) function blocks forever. Is there a way to make it non-blocking, giving me a chance to do something else if no device is listening to the serial port?
System.out.println("Writing to device");
outputStream.write("AT".getBytes()); //  <- program hangs here if no device is present
outputStream.write((byte) 0x0D);
System.out.println("Done");
//Then try to read AT....OK to see if modem is responding

Answer 1

You should be able to check for the presence/absence of a modem by chacking the state of the incoming signals
e.g. DSR=data set ready should be asserted if the modem is ready.
You may find this link helpful
http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html