Error: "No error in nativeDrain" caused by OutputStream.flush()

I have the following problem: when I want to flush the OutputStream, RxTx return an error. The goal is to send sms using modem key. So where was I wrong?

I searched and found nothing, I don't know what causes the problem !

I think the error message comes from the RxTx library but I'm not sure. I've already tried without flushing, but it didn't work either. So please help me <3 !

This is the actual code of my class:

package fr.ryfax.smscontroller.main;

import java.io.*;
import java.util.ArrayList;

import gnu.io.*;

public class USBModem {

    private CommPortIdentifier PORT_ID;
    private final String PORT;
    private final int BITRATE;
    private final String CENTER;

    private final char ENTER = 13;
    private final char CTRLZ = 26;

    public USBModem(String PORT, int BITRATE, String SMSCENTER) {

        try {
            this.PORT_ID = CommPortIdentifier.getPortIdentifier(PORT);
        }catch(Exception e) {
            this.PORT_ID = null;
            System.err.println("USBModem Error: Unknown port!");
        }

        this.PORT    = PORT;
        this.BITRATE = BITRATE;
        this.CENTER  = SMSCENTER;

    }

    public void sendSMS(String TO, String MSG) throws Exception {

        SerialPort serial         = (SerialPort) PORT_ID.open(this.PORT, 2000);
        //InputStream inputStream   = serial.getInputStream();

        serial.setSerialPortParams(this.BITRATE, //115200
                SerialPort.DATABITS_8,           //Bit de données
                SerialPort.STOPBITS_1,           //Bit d'arrêt
                SerialPort.PARITY_NONE           //Parité
        );
        serial.setFlowControlMode(SerialPort.FLOWCONTROL_NONE); //Flux

        ArrayList<String> commands = new ArrayList<String>();

        commands.add("AT" + ENTER);
        commands.add("AT+CMGF=1" + ENTER);
        commands.add("AT+CSCA=\"" + CENTER + "\"" + ENTER);
        commands.add("AT+CSCA=\"" + TO + "\"" + ENTER);
        commands.add(MSG + CTRLZ);

        sendCommands(commands, serial);

        System.out.println("[MOI] -> [" + TO + "]" + " : " + MSG);
    }

    public void sendCommands(ArrayList<String> commands, SerialPort serial) throws Exception {
        OutputStream outputStream = serial.getOutputStream();
        for(String command : commands) {
            outputStream.flush();
            outputStream.write(command.getBytes());
            Thread.sleep(100);
        }
        Thread.sleep(3000);

        serial.close();
        outputStream.close();
    }
}

Output:

Exception in thread "main" java.io.IOException: No error in nativeDrain
    at gnu.io.RXTXPort.nativeDrain(Native Method)
    at gnu.io.RXTXPort$SerialOutputStream.flush(RXTXPort.java:1248)
    at fr.ryfax.smscontroller.main.USBModem.sendCommands(USBModem.java:61)
    at fr.ryfax.smscontroller.main.USBModem.sendSMS(USBModem.java:53)
    at fr.ryfax.smscontroller.main.Main.main(Main.java:21)

It makes more sense to call outputStream.flush after outputStream.write, so do that. And speaking of switching order, call outputStream.close before serial.close.

Then find a large A3 sheet of paper, a red pen and write 1000 times

I will never use Thread.sleep as a substitute for reading and parsing responses from a modem.

I will never use Thread.sleep as a substitute for reading and parsing responses from a modem.

I will never use Thread.sleep as a substitute for reading and parsing responses from a modem.

I will never use Thread.sleep as a substitute for reading and parsing responses from a modem.

...

When sending AT commands to a modem, you MUST read and parse everything it sends back to you.

Your second AT+CSCA is supposed to be AT+CMGS, and for that command you MUST wait for the "ready to receive payload data" prompt before sending the SMS payload.