Reading file from serial port in Java

问题

i'm beginner in java technology, I have to read file from port. Frst I'll write "FLASH" to outputstream then I'll get response as a "FLASH_OK" from target device, after getting FLASH_OK as response then again i have to write name of the file which i want,but problem is its not writing file name to outputstream, below is my code. Please help me.

package writeToPort;

import java.awt.Toolkit;
import java.io.*;
import java.util.*;

import javax.comm.*;
import javax.swing.JOptionPane;

import constants.Constants;

public class Flashwriter implements SerialPortEventListener {
Enumeration portList;
CommPortIdentifier portId;
String messageString = "\r\nFLASH\r\n";
SerialPort serialPort;
OutputStream outputStream;
InputStream inputStream;
Thread readThread;
String one, two;
String test = "ONLINE";
String[] dispArray = new String[1];
int i = 0;

byte[] readBufferArray;
int numBytes;
String response;
FileOutputStream out;
final int FLASH = 1, FILENAME = 2;
int number;

File winFile;

public static void main(String[] args) throws IOException {
    Flashwriter sm = new Flashwriter();
    sm.FlashWriteMethod();
}

public void FlashWriteMethod() throws IOException {

    portList = CommPortIdentifier.getPortIdentifiers();
    winFile = new File("D:\\testing\\out.FLS");

    while (portList.hasMoreElements()) {
        portId = (CommPortIdentifier) portList.nextElement();
        if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
            if (portId.getName().equals("COM2")) {
                try {
                    serialPort = (SerialPort) portId.open("SimpleWriteApp",
                            1000);
                } catch (PortInUseException e) {
                }

                try {
                    inputStream = serialPort.getInputStream();

                    System.out.println(" Input Stream... " + inputStream);
                } catch (IOException e) {
                    System.out.println("IO Exception");
                }
                try {
                    serialPort.addEventListener(this);

                } catch (TooManyListenersException e) {
                    System.out.println("Tooo many Listener exception");
                }
                serialPort.notifyOnDataAvailable(true);

                try {
                    outputStream = serialPort.getOutputStream();
                    inputStream = serialPort.getInputStream();
                } catch (IOException e) {
                }
                try {
                    serialPort.setSerialPortParams(9600,
                            SerialPort.DATABITS_8, SerialPort.STOPBITS_1,
                            SerialPort.PARITY_NONE);
                    serialPort
                            .setFlowControlMode(SerialPort.FLOWCONTROL_NONE);
                                            number = FLASH;
                    sendRequest(number);

                } catch (UnsupportedCommOperationException e) {
                }

            }
        }
    }
}

public void serialEvent(SerialPortEvent event) {
    SerialPort port = (SerialPort) event.getSource();

    switch (event.getEventType()) {
    case SerialPortEvent.DATA_AVAILABLE:
        try {
            if (inputStream.available() > 0) {
                numBytes = inputStream.available();
                readBufferArray = new byte[numBytes];
                int readBytes = inputStream.read(readBufferArray);

                one = new String(readBufferArray);
                System.out.println("readBytes " + one);
            }
            if (one.indexOf("FLASH_") > -1 & !(one.indexOf("FLASH_F") > -1)) {
                System.out.println("got message");
                response = "FLASH_OK";
                number = FILENAME;
                sendRequest(number);
            }

            out = new FileOutputStream(winFile, true);
            out.write(readBufferArray);
            out.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        readBufferArray = null;
        // break;
    }


}


public void sendRequest(int num) {
    switch (num) {
    case FLASH:
        try {
            outputStream.write(messageString.getBytes());
            outputStream.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
        break;
    case FILENAME:
        try {
            outputStream.write("\r\n26-02-08.FLS\r\n".getBytes());
            outputStream.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
        break;

    }
}

}

回答1:

Have you tested with a Serial Port Emulator software?

When I did this kind of app for college, our professor told us to build the app and test it using an emulator, since it's much cheaper and less error prone.

While searching for google you can find some softwares that do that. I don't remember exactly the one we used at that time, but it worked quite well.

I mean products like this: Eterlogic - Virtual Serial Ports Emulator, but that's just an example (and I haven't tested this software, I just googled it)

回答2:

You are erroneously assuming that full messages are always going to be received. Instead, when a serial event is triggered, only part of the message may be available. For example, you may get an event and read "FLAS" and a subsequent event will give "H_OK". You need to adapt your code to something like this:

// member variables
byte [] receiveBuffer = new byte[BUFFER_LENGTH];
int receiveIndex = 0;

// Receive code

receiveIndex +=
   inputStream.read(receiveBuffer, receiveIndex, BUFFER_LENGTH - receiveIndex);

回答3:

Sorry I can't help you with the Java code but are you sure the data "FLASH" is actually being sent on your serial port ? When I'm having this kind of problem I usually use an oscilloscope to look on the TX pin on the serial port and check if I can "see" the data being sent (the data burst will be brief but you will be able to see it). If you can see it use the scope to look on the RX pin of the serial port and see if you can see the "FLASH_OK" response actually being sent.

Nine out of ten times the problem isn't the software but a hardware issue often due to handshaking pins being incorrectly connected.

Good luck with this.

来源：https://stackoverflow.com/questions/560328/reading-file-from-serial-port-in-java