If there is data, how is the stream returning zero bytes? - javafx

Question

I have a RXTX project that I'm working on. I have it set ups as follows:
public void doConnect(ActionEvent event)
{
String selectedPort = (String)connectTabController.portList.getValue();
System.out.println("Connecting to: " + selectedPort);
selectedPortIdentifier = (CommPortIdentifier)portMap.get(selectedPort);
CommPort commPort = null;
try
{
commPort = selectedPortIdentifier.open("AT QC ReponseTime", TIMEOUT);
serialPort = (SerialPort)commPort;
setConnected(true);
if (isConnected)
{
if (initIOStream() == true)
{
initListener();
System.out.println("Initializing listener");
connectTabController.gui_changeStatusLabel("Device Connected!");
}
}
}
catch (PortInUseException e)
{
System.out.println("Port In use! " + e.toString());
}
catch (Exception e)
{
System.out.println("Failed to open! " + e.toString());
}
}
public boolean initIOStream()
{
//return value for whether opening the streams is successful or not
boolean successful = false;
try {
//
input = serialPort.getInputStream();
output = serialPort.getOutputStream();
writeData(RESETTPOD);
System.out.println("Writing Reset command");
successful = true;
System.out.println("IO Stream opened successfully!");
return successful;
}
catch (IOException e) {
System.out.println("I/O Streams failed to open. (" + e.toString() + ")");
return successful;
}
}
public void initListener()
{
try
{
serialPort.addEventListener(this);
serialPort.notifyOnDataAvailable(true);
}
catch (TooManyListenersException e)
{
System.out.println("Too many listeners. (" + e.toString() + ")");
}
}
That's how the connection is made, and it has a listener that's supposed to notify when data is available, which triggers the following:
#Override
public void serialEvent(SerialPortEvent evt) {
BufferedReader reader = null;
if (evt.getEventType() == SerialPortEvent.DATA_AVAILABLE)
{
try
{
reader = new BufferedReader(new InputStreamReader(input));
if (reader.ready())
{
fullLine = reader.readLine();
System.out.println(fullLine + "\n");
}
}
catch (Exception e)
{
System.out.println("#SerialEvent Failed to read data. (" + e.toString() + ")");
}
}
}
However, I keep getting "UNDERLYING INPUT STREAM RETURNED ZERO BYTES"
This makes no sense, since if there is nothing to read then the listener shouldnt be triggered int he first place. I tried running the app and I keep getting this error message around every 1/3 second, which corresponds to the burst-output of the device that's sending data. (which works fine in programs like PuttY)

Answer 1

If you are going to use the BufferedReader, take a look at the refence API document for javax.comm, CommPort and getInputStream. Then try using different settings for threshold and receive timeout.
eg).
serialPort.enableReceiveThreshold(3);
serialPort.enableReceiveTimeout(1);
https://docs.oracle.com/cd/E17802_01/products/products/javacomm/reference/api/