Perché lo status di porto franco COM4 del mio computer, mentre il mio modem telefono lo usa?

Question

Ecco il mio codice:

import java.io.*;
import java.util.*;
import javax.comm.*;

public class SMS {


    public static void main(String[] args) {
            Enumeration lists=CommPortIdentifier.getPortIdentifiers();
            System.out.println(CommPortIdentifier.PORT_SERIAL);
            System.out.println(lists.hasMoreElements());
            while (lists.hasMoreElements()){
                CommPortIdentifier cn=(CommPortIdentifier)lists.nextElement();

                if ((CommPortIdentifier.PORT_SERIAL==cn.getPortType())){
                    System.out.println("Name is serail port "+cn.getName()+" Owned status "+cn.isCurrentlyOwned());

                    try{
                        SerialPort port1=(SerialPort)cn.open("ComControl",800000);
                        port1.setSerialPortParams(9600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
                        System.out.println("Before get stream");
                        OutputStream out=port1.getOutputStream();
                        InputStream input=port1.getInputStream();
                        System.out.println("Before write");
                        out.write("AT".getBytes());
                        System.out.println("After write");
                        int sample=0;
                        //while((( sample=input.read())!=-1)){
                        System.out.println("Before read");
                            //System.out.println(input.read() + "Testing ");
                        //}
                            System.out.println("After read");
                        System.out.println("Receive timeout is "+port1.getReceiveTimeout());
                    }catch(Exception e){
                        System.err.println(e.getMessage());
                    }
                }

                else{
                    System.out.println("Name is parallel port "+cn.getName()+" Owned status "+cn.isCurrentlyOwned()+cn.getPortType()+"    ");
                }
            }
    }

}

Questa è l'uscita:

1
true
Name is serail port COM1 Owned status false
Before get stream
Before write
After write
Before read
After read
Receive timeout is -1
Name is serail port COM2 Owned status false
Before get stream
Before write
After write
Before read
After read
Receive timeout is -1
Name is serail port COM3 Owned status false
Before get stream
Before write
After write
Before read
After read
Receive timeout is -1
Name is serail port COM4 Owned status false
Before get stream
Before write
After write
Before read
After read
Receive timeout is -1
Name is parallel port LPT1 Owned status false2    
Name is parallel port LPT2 Owned status false2    

La mia porta COM4 viene utilizzata da mio modem telefono, ma secondo il codice il suo stato è libero. C'è qualcosa che ho perso il codice e come posso risolvere tali difficoltà?

Answer 1

potrebbe essere che qualunque sia il software che controlla il telefono è in modalità sleep, o qualcosa del genere?