Java com端口读写问题

Question

Firstly let me introduce my program. My application pure java and use comm jar for com port. I already added

1. win32com.dll - jre/bin
2. comm.jar - jre/lib/ext
3. java.comm.properties - jre/liv

The following is my program

import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;

import javax.comm.CommPortIdentifier;
import javax.comm.SerialPort;

public class PortReaderWriter
{
    static Enumeration<?> ports;
    static CommPortIdentifier portId;
    static InputStream inputStream;
    static OutputStream outputStream;
    static SerialPort serialPort;
    static String messageString = "abc";

    public static void main(String[] args) throws Exception
    {
        try
        {
            ports = CommPortIdentifier.getPortIdentifiers();

            while (ports.hasMoreElements())
            {
                portId = (CommPortIdentifier) ports.nextElement();
                System.out.println("Port " + portId.getName());

                if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL)
                {
                    if (portId.getName().equals("COM1"))
                    {
                        System.out.println("====================");
                        System.out.println("COM1 found");

                        serialPort = (SerialPort) portId.open("PortReaderWriter", 2000);
                        serialPort
                                .setSerialPortParams(9600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);

                        outputStream = serialPort.getOutputStream();
                        outputStream.write(messageString.getBytes());
                        System.out.println(messageString.getBytes() + "  Successfully Sent!");

                        inputStream = serialPort.getInputStream();
                        byte[] readBuffer = new byte[2048];
                        while (inputStream.available() > 0)
                        {
                            int numBytes = inputStream.read(readBuffer);
                            System.out.println("numBytes " + numBytes);
                        }
                        System.out.print(new String(readBuffer));

                        outputStream = serialPort.getOutputStream();
                        outputStream.write(messageString.getBytes());
                        System.out.println(messageString.getBytes() + "  Successfully Sent!");

                        System.out.println("====================");
                    }
                }
            }
        } catch (Exception e)
        {
            e.printStackTrace();
        }
    }
}

The output is

Port COM3
Port COM1
====================
COM1 found
[B@1a52fdf  Successfully Sent!

====================
Port LPT1
Port LPT2

But My expected output is

COM1 found
[B@1a52fdf  Successfully Sent!
abc
====================
Port LPT1
Port LPT2

In the program, I am not sure "abc" is sent or not and in the output I can not see. Please help me is there any required to add or change. Thanks in advance!

Answer 1

The messageString.getBytes() in the following statement returns a byte array instead of the string itself :

System.out.println(messageString.getBytes() + "  Successfully Sent!");

and that is why you get a [B@1a52fdf instead of the message itself.

Of course, when you send the data you send a byte array, but if you wish to see what was sent in a String form, you could use the below :

System.out.println(messageString + "  Successfully Sent!");

Additionally, the statement System.out.println("Port " + portId.getName()); prints every Port name; if you only wish to show the port name for ports that have been found as per your criteria (as the Port COM3 and Port COM1 ar missing from your desired output), you could omit this statement.