Java RXTX串口可以发送数据，但接收不到数据。

package com.red.test;



import gnu.io.CommPortIdentifier;

import gnu.io.NoSuchPortException;

import gnu.io.PortInUseException;

import gnu.io.SerialPort;

import gnu.io.SerialPortEvent;

import gnu.io.SerialPortEventListener;

import gnu.io.UnsupportedCommOperationException;



import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.util.Enumeration;

import java.util.Timer;

import java.util.TimerTask;

import java.util.TooManyListenersException;



public class Demo implements SerialPortEventListener{

	

	protected static CommPortIdentifier portid = null;  //通讯端口标识符

	protected static SerialPort comPort = null;         //串行端口

	protected int BAUD = 9600;  //波特率

	protected int DATABITS = SerialPort.DATABITS_8;;  //数据位

	protected int STOPBITS = SerialPort.STOPBITS_1;  //停止位

	protected int PARITY = SerialPort.PARITY_NONE;  //奇偶检验

	private static OutputStream oStream;    //输出流

	private static InputStream iStream;     //输入流

	StringBuilder buf = new StringBuilder(128);

	

	public static void main(String[] args) {

		Timer t = new Timer();

        

		t.schedule(new TimerTask() {

		@Override

		public void run() {

			

		Demo test = new Demo();

		// 查看所有串口

		test.listPortChoices();

		//设置串口号

		test.setSerialPortNumber();

		

		}},3000,3000);

	}

	

	/**

	 * 读取所有串口名字

	 */

	 private void listPortChoices() {

		 CommPortIdentifier portId;

		 Enumeration en = CommPortIdentifier.getPortIdentifiers();

		 // iterate through the ports.

		 while (en.hasMoreElements()) {

			 portId = (CommPortIdentifier) en.nextElement();

			 if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {

				 System.out.println(portId.getName());

			 }

		 }

	 }

	 

	 /**

	  * 设置串口号

	  * @param Port

	  * @return

	  */

	 private void setSerialPortNumber() {

	  

		 String osName = null;

		 String osname = System.getProperty("os.name", "").toLowerCase();

		 if (osname.startsWith("windows")) {

			 // windows

			 osName = "COM1";

		 } else if (osname.startsWith("linux")) {

			 // linux

			 osName = "/dev/ttyS1";

		 }

		  

		 try {

			 portid = CommPortIdentifier.getPortIdentifier(osName);

			 // portid = CommPortIdentifier.getPortIdentifier(Port);

			 if(portid.isCurrentlyOwned()){

				 System.out.println("端口在使用");

			 }else{

				 comPort = (SerialPort) portid.open(this.getClass().getName(), 1000);

			 }

		 } catch (PortInUseException e) {

			 System.out.println("端口被占用");

			 e.printStackTrace();

		 

		 } catch (NoSuchPortException e) {

			 System.out.println("端口不存在");

			 e.printStackTrace();

		 }



		 try {

			iStream = comPort.getInputStream(); //从COM1获取数据

			oStream = comPort.getOutputStream();

		 } catch (IOException e) {

				e.printStackTrace();

		}

		 

		 

		try {

			comPort.addEventListener(this);       //给当前串口增加一个监听器

			comPort.notifyOnDataAvailable(true);  //当有数据是通知

		} catch (TooManyListenersException e) {

			e.printStackTrace();

		}

		

		try {

			//设置串口参数依次为(波特率,数据位,停止位,奇偶检验)

			comPort.setSerialPortParams(this.BAUD, this.DATABITS, this.STOPBITS, this.PARITY);

		} catch (UnsupportedCommOperationException e) {

			System.out.println("端口操作命令不支持");

			e.printStackTrace();

		}

		

		try {

			

			//# testData

			String testData = "1";

			oStream.write(testData.getBytes());

			

			

			iStream.close();

			comPort.close();

		} catch (IOException e) {

			e.printStackTrace();

		}

	 }



	@Override

	public void serialEvent(SerialPortEvent event) {

		switch (event.getEventType()) {

			case SerialPortEvent.BI:

			case SerialPortEvent.OE:

			case SerialPortEvent.FE:

			case SerialPortEvent.PE:

			case SerialPortEvent.CD:

			case SerialPortEvent.CTS:

			case SerialPortEvent.DSR:

			case SerialPortEvent.RI:

			case SerialPortEvent.OUTPUT_BUFFER_EMPTY:

				break;

			case SerialPortEvent.DATA_AVAILABLE:// 当有可用数据时读取数据,并且给串口返回数据

				byte[] readBuffer = new byte[20];;

				try {

					char b;

					while (iStream.available() > 0) {

						b = (char)iStream.read(readBuffer);

						buf.append(b);

					}

				} catch (IOException e) {

					System.out.println(e.toString());

				}

				break;

		}

	}

}