import jssc.SerialPort;
import jssc.SerialPortEvent;
import jssc.SerialPortEventListener;
import jssc.SerialPortException;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
 
public class Test {
 
    public static void main(String[] args) throws IOException, InterruptedException {
        SerialPortImpl sp = new SerialPortImpl("/dev/ttyUSB0");
 
        ProcessBuilder processBuilder = new ProcessBuilder("socat", "-d", "-d", "pty,raw,echo=0", "pty,raw,echo=0");
        processBuilder.redirectErrorStream(true);
        Process process = processBuilder.start();
        BufferedReader in = new BufferedReader(new InputStreamReader(process.getInputStream()));
        String port1 = null, port2 = null, line;
        while ((line = in.readLine()) != null) {
            if (line.contains("] ")) {
                line = line.substring(line.indexOf("] ") + 2);
                if (line.startsWith("N PTY is ")) {
                    line = line.replace("N PTY is ", "");
                    if (port1 == null) {
                        port1 = line;
 
                    } else {
                        port2 = line;
                        break;
                    }
                }
            }
        }
 
        SerialPortImpl mockedSerialPort = new SerialPortImpl(port1);
        mockedSerialPort.addListener(new Forwarder(sp));
        sp.addListener(new Forwarder(mockedSerialPort));
 
        //System.out.println(port1);
        System.out.println(port2);
        process.waitFor();
        in.close();
    }
 
    protected static class Forwarder {
 
        private SerialPortImpl forwardTo;
 
        Forwarder(SerialPortImpl forwardTo) {
            this.forwardTo = forwardTo;
        }
 
        void onPortMessage(String msg) {
            System.out.println("FORWARDING     " + msg);
            forwardTo.print(msg);
        }
    }
 
    public static class SerialPortImpl implements SerialPortEventListener {
 
        ArrayList<Forwarder> listeners = new ArrayList<>();
        SerialPort serialPort;
 
        SerialPortImpl(String port) {
            connect(port);
        }
 
        boolean isConnected() {
            return (serialPort != null) && serialPort.isOpened();
        }
 
        void addListener(Forwarder listener) {
            if (listeners.contains(listener)) {
                System.out.println("Listener already in the list!");
 
            } else {
                listeners.add(listener);
            }
        }
 
        void connect(String port) {
            serialPort = new SerialPort(port);
            try {
                serialPort.openPort();
                serialPort.setParams(SerialPort.BAUDRATE_9600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
                serialPort.setEventsMask(SerialPort.MASK_RXCHAR);
                serialPort.addEventListener(this);
 
            } catch (SerialPortException e) {
                e.printStackTrace();
            }
        }
 
        void print(String message) {
            if (isConnected()) {
                new Thread(() -> {
                    try {
                        if (!serialPort.writeBytes(message.getBytes())) {
                            System.out.println("error writing");
                        }
 
                    } catch (SerialPortException e) {
                        e.printStackTrace();
                    }
                }, "Serial data sender").start();
 
            } else {
                System.out.println("not connected");
            }
        }
 
        @Override
        public void serialEvent(SerialPortEvent portEvent) {
            try {
                String msg = serialPort.readString();
                if ((msg != null) && (!msg.equals(""))) {
                    for (Forwarder l : listeners) {
                        l.onPortMessage(msg);
                    }
                }
 
            } catch (SerialPortException e) {
                e.printStackTrace();
            }
        }
    }
}