连接到 rfcomm0 的 Java rxtx 代码不起作用

Question

我已经成功地将我的 arduino uno R3 与蓝牙伴侣模块连接起来，并且能够通过蓝牙将数据发送到运行 Ubuntu 12.04 的笔记本电脑。 （使用串口协议）。数据在 rfcomm0 上接收。

以下代码显示接收到的数据：sudo screen /dev/rfcomm0

现在我在 Java 程序中读取这些数据时遇到了问题。我已经参考了http://playground.arduino.cc/Interfacing/Java 的代码。这使用 rxtx 库来访问串行端口。

代码如下：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import gnu.io.CommPortIdentifier; 
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent; 
import gnu.io.SerialPortEventListener; 
import java.util.Enumeration;


public class SerialTest implements SerialPortEventListener {
    SerialPort serialPort;
    /** The port we're normally going to use. */
    private static final String PORT_NAMES[] = { 
            "/dev/tty.usbserial-A9007UX1", // Mac OS X
            "/dev/ttyUSB0", // Linux
            "COM3", // Windows
//          "/dev/ttyACM0" // Ubuntu
            "/dev/rfcomm0" // Ubuntu Bluetooth
    };
    /**
    * A BufferedReader which will be fed by a InputStreamReader 
    * converting the bytes into characters 
    * making the displayed results codepage independent
    */
    private BufferedReader input;
    /** The output stream to the port */
    private OutputStream output;
    /** Milliseconds to block while waiting for port open */
    private static final int TIME_OUT = 2000;
    /** Default bits per second for COM port. */
    private static final int DATA_RATE = 9600;

    public void initialize() {
        CommPortIdentifier portId = null;
        Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();

        //First, Find an instance of serial port as set in PORT_NAMES.
        while (portEnum.hasMoreElements()) {
            CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
            for (String portName : PORT_NAMES) {
                if (currPortId.getName().equals(portName)) {
                    portId = currPortId;
                    break;
                }
            }
        }
        if (portId == null) {
            System.out.println("Could not find COM port.");
            return;
        }

        try {
            // open serial port, and use class name for the appName.
            serialPort = (SerialPort) portId.open(this.getClass().getName(),
                    TIME_OUT);

            // set port parameters
            serialPort.setSerialPortParams(DATA_RATE,
                    SerialPort.DATABITS_8,
                    SerialPort.STOPBITS_1,
                    SerialPort.PARITY_NONE);

            // open the streams
            input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
            output = serialPort.getOutputStream();

            // add event listeners
            serialPort.addEventListener(this);
            serialPort.notifyOnDataAvailable(true);
        } catch (Exception e) {
            System.err.println(e.toString());
        }
    }

    /**
     * This should be called when you stop using the port.
     * This will prevent port locking on platforms like Linux.
     */
    public synchronized void close() {
        if (serialPort != null) {
            serialPort.removeEventListener();
            serialPort.close();
        }
    }

    /**
     * Handle an event on the serial port. Read the data and print it.
     */
    public synchronized void serialEvent(SerialPortEvent oEvent) {
        if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
            try {
                String inputLine=input.readLine();
                System.out.println(inputLine);
            } catch (Exception e) {
                System.err.println(e.toString());
            }
        }
        // Ignore all the other eventTypes, but you should consider the other ones.
    }

    public static void main(String[] args) throws Exception {
        SerialTest main = new SerialTest();
        main.initialize();
        Thread t=new Thread() {
            public void run() {
                //the following line will keep this app alive for 10 seconds,
                //waiting for events to occur and responding to them (printing incoming messages to console).
                try {Thread.sleep(10000);} catch (InterruptedException ie) {}
            }
        };
        System.out.println("Started");
        t.start();
        t.join();
        main.close();
        System.out.println("Stopped");
    }
}

此程序编译成功，但执行时显示："Could not find COM port."

注意：当从 USB 端口 /dev/ttyACM0 读取数据时，此代码可以完美运行。当我尝试从蓝牙端口/dev/rfcomm0 读取数据时出现问题。

所以基本上我需要一个 java 程序来读取 rfcomm0 端口。非常感谢任何帮助。

Answer 1

感谢@angelatlarge 的建议。

问题是java程序没有访问/dev/rfcomm0的权限。

提供权限的命令：sudo chmod a+rw /dev/rfcomm0

所以授予/dev/rfcomm0 的权限为我解决了这个问题。 现在java程序可以从rfcomm0端口读取数据了。