/** @see com.svhelloworld.knotlog.engine.sources.StreamedSource#open() */
@Override
public InputStream open() {
try {
// make sure the specified port is available
CommPortIdentifier identifier = CommPortIdentifier.getPortIdentifier(config.getName());
if (identifier.isCurrentlyOwned()) {
throw new SerialPortOccupiedException(
config.getName() + " port is currently opened by another application");
}
// open up the port
CommPort port = identifier.open(getOwnerName(), PORT_TIMEOUT);
if (port instanceof SerialPort) {
// configure serial port
serialPort = (SerialPort) port;
serialPort.setSerialPortParams(
config.getBaudRate(),
config.getDataBits().getRXTXConstant(),
config.getStopBit().getRXTXConstant(),
config.getParity().getRXTXConstant());
/*
* the following 2 lines fix the exception:
* "IOException: Underlying input stream returned zero bytes"
* that is thrown when we read from the InputStream.
*/
serialPort.enableReceiveTimeout(PORT_TIMEOUT);
serialPort.enableReceiveThreshold(0);
InputStream is = serialPort.getInputStream();
return is;
}
// not a serial port
throw new SerialPortException("must operate against a serial port");
} catch (PortInUseException e) {
throw new SerialPortOccupiedException(e.getMessage(), e);
} catch (Exception e) {
throw new SerialPortException(e.getMessage(), e);
}
}
/**
* Opens the communication port.
*
* @throws Exception if an error occurs.
*/
public void open() throws Exception {
// If this is Linux then first of all we need to check that
// device file exists. Otherwise call to m_PortIdentifyer.open()
// method will crash JVM.
// It is ugly patch but it is too late...
if (SystemUtils.IS_OS_LINUX) {
File portDevFile = new File(m_Parameters.getPortName());
if (!portDevFile.exists()) {
throw new Exception(
"Modbus serial device " + m_Parameters.getPortName() + " doesn't exist!");
}
}
// 1. obtain a CommPortIdentifier instance
try {
m_PortIdentifyer = CommPortIdentifier.getPortIdentifier(m_Parameters.getPortName());
} catch (NoSuchPortException e) {
final String errMsg =
"Could not get port identifier, maybe insufficient permissions. " + e.getMessage();
logger.debug(errMsg);
throw new Exception(errMsg);
}
logger.trace("Got Port Identifier");
// 2. open the port, wait for given timeout
try {
m_SerialPort = (SerialPort) m_PortIdentifyer.open("Modbus Serial Master", 30000);
} catch (PortInUseException e) {
logger.debug("open port failed: " + e.getMessage());
throw new Exception(e.getMessage());
}
logger.trace("Got Serial Port");
// 3. set the parameters
try {
setConnectionParameters();
} catch (Exception e) {
// ensure it is closed
m_SerialPort.close();
logger.debug("parameter setup failed: " + e.getMessage());
throw e;
}
if (Modbus.SERIAL_ENCODING_ASCII.equals(m_Parameters.getEncoding())) {
m_Transport = new ModbusASCIITransport();
} else if (Modbus.SERIAL_ENCODING_RTU.equals(m_Parameters.getEncoding())) {
m_Transport = new ModbusRTUTransport();
setReceiveTimeout(m_Parameters.getReceiveTimeout()); // just here for the moment.
} else if (Modbus.SERIAL_ENCODING_BIN.equals(m_Parameters.getEncoding())) {
m_Transport = new ModbusBINTransport();
}
m_Transport.setEcho(m_Parameters.isEcho());
// Open the input and output streams for the connection. If they won't
// open, close the port before throwing an exception.
try {
m_SerialIn = m_SerialPort.getInputStream();
m_Transport.setCommPort(m_SerialPort);
// m_Transport.prepareStreams(m_SerialIn,
// m_SerialPort.getOutputStream());
} catch (IOException e) {
m_SerialPort.close();
logger.debug(e.getMessage());
throw new Exception("Error opening i/o streams");
}
logger.trace("i/o Streams prepared");
// Add this object as an event listener for the serial port.
try {
m_SerialPort.addEventListener(this);
} catch (TooManyListenersException e) {
m_SerialPort.close();
final String errMsg = "too many listeners added";
logger.debug("{}: {}", errMsg, e.getMessage());
throw new Exception(errMsg);
}
// Set notifyOnBreakInterrup to allow event driven break handling.
m_SerialPort.notifyOnBreakInterrupt(true);
m_Open = true;
} // open
