Example

package custis.packhaus.modem;

import gnu.io.*;

import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Paths;

public class Application {
    public static void main(String[] args) throws IOException, InterruptedException, PortInUseException, NoSuchPortException, UnsupportedCommOperationException {

        CommPortIdentifier real = CommPortIdentifier.getPortIdentifier("COM9");
        CommPort commPort = real.open("ymodem", 4000);
        try {
            if (commPort instanceof SerialPort) {
                SerialPort serialPort = (SerialPort) commPort;
                //serialPort.setBaudBase(115200);
                serialPort.setSerialPortParams(115200, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
                //serialPort.setFlowControlMode(SerialPort.FLOWCONTROL_NONE);

                Thread.sleep(10);

                YModem modem = new YModem(serialPort.getInputStream(), serialPort.getOutputStream());

                //modem.receiveFilesInDirectory(Paths.get("."));

                modem.send(Paths.get("RNTMP.FLD"), Paths.get("RNTMP.DAT"));
            }
        }
        finally {
            commPort.close();
        }

    }
}