java的com口通讯

import gnu.io.CommPortIdentifier;  
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.util.Enumeration;  
import java.util.TooManyListenersException;  
  
public class SimpleRead implements Runnable,SerialPortEventListener {  
    static CommPortIdentifier portId;  
  
    static Enumeration portList;  
  
    InputStream inputStream;  
  
    SerialPort serialPort;  
  
    Thread readThread;  
  
    public static void main(String[] args) {  
  
        String com="4";  
        if(args!=null&&args.length>=1)  
        com=args[0];  
          
        portList = CommPortIdentifier.getPortIdentifiers();  
        // 检索系统串口  
        while (portList.hasMoreElements()) {  
            portId = (CommPortIdentifier) portList.nextElement();  
          
            /*如果端口类型是串口，则打印出其端口信息*/   
            if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {  
                System.out.println("------------------------");  
                System.out.println("系统可用串口: "+portId.getName());  
                System.out.println("------------------------");  
                // 指定COM口  
                if (portId.getName().equals("COM"+com)) {  
                    System.out.println("找到COM"+com+"口,初始化...");  
                    SimpleRead reader = new SimpleRead();  
                }else{  
                    System.out.println("无法找到COM"+com+"口,请重新指定...");  
                }  
            }  
        }  
    }  
  
    public SimpleRead() {  
        try {  
        // 打开COM串口 2000 设置毫秒数 超时等待时间  
          
            serialPort = (SerialPort) portId.open("SimpleReadApp",2000);  
            System.out.println("COM口打开成功！");  
  
        } catch (PortInUseException e) {  
            System.out.println("端口被占用");  
        }  
        try {  
            inputStream = serialPort.getInputStream();  
            System.out.println("获得输入流...");  
        } catch (IOException e) {  
        }  
        //进行端口监听,当事件发生自动调用 serialEvent方法  
        try {  
            serialPort.addEventListener(this);  
        } catch (TooManyListenersException e) {  
        }  
        serialPort.notifyOnDataAvailable(true);  
          
        //设置通讯位  
        try {  
            System.out.println("设置通讯位...");  
            serialPort.setSerialPortParams(115200,// 设置波特率  
                    SerialPort.DATABITS_8,// 数据位数  
                    SerialPort.STOPBITS_1,// 停止位  
                    SerialPort.PARITY_NONE);// 奇偶位  
        } catch (UnsupportedCommOperationException e) {  
        }  
  
        // 启动线程，监听  
        readThread = new Thread(this);//线程负责每接收一次数据休眠20秒钟  
        readThread.start();  
    }  
  
    public void run() {  
        try {  
            System.out.println("监听...");  
            Thread.sleep(20000);//休息20秒  
              
        } catch (Exception e) {  
        }  
    }  
    // 处理侦听到的串口事件  
    public synchronized void serialEvent(SerialPortEvent event) {  
    //    System.out.println("接收数据...rn");  
          
        switch (event.getEventType()) {  
        case SerialPortEvent.BI://BI - 通讯中断.  
        case SerialPortEvent.OE://OE - 溢位错误.  
        case SerialPortEvent.FE://FE - 帧错误.  
        case SerialPortEvent.PE://PE - 奇偶校验错.  
        case SerialPortEvent.CD://CD - 载波检测.  
        case SerialPortEvent.CTS://CTS - 清除发送.  
        case SerialPortEvent.DSR://DSR - 数据设备准备好.  
        case SerialPortEvent.RI://RI - 　振铃指示.  
        case SerialPortEvent.OUTPUT_BUFFER_EMPTY://OUTPUT_BUFFER_EMPTY - 输出缓冲区已清空  
            break;  
        case SerialPortEvent.DATA_AVAILABLE://DATA_AVAILABLE - 有数据到达  
              
              
            byte[] readBuffer = new byte[10000];  
  
            try {  
                //读数据  
                while (inputStream.available() > 0) {  
                    int numBytes = inputStream.read(readBuffer);  
                }  
              
                String str=new String(readBuffer);  
                if(str.equals("exit")){  
                    inputStream.close();serialPort.close();  
                }  
                //输出内容  
                System.out.println("<------开始------->");  
                System.out.println(str+"==============");  
                System.out.println("<------结束------->");  
                System.out.println("                    ");  
            } catch (IOException e) {  
            }  
            break;  
        }  
    }  
}