javaSwing中rs232串口通讯怎么样判断端口状态（断开，连接，丢失）

Question

package com.ehealth.util.measure.commport;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.LinkedList;

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

import org.apache.log4j.Logger;

import com.ehealth.util.CommonUtil;
import com.ehealth.util.measure.commport.event.UartConnListener;

public abstract class UartConn {
private static final Logger logger = Logger.getLogger(UartConn.class);

private LinkedList<UartConnListener> listeners = new LinkedList<UartConnListener>();//添加监听事件放到LinkedList中

protected SerialPort serialPort;//串行端口
static OutputStream outputStream;//输出流
       InputStream inputStream;//输入流
protected UartConn(String commPort, int baudrate, int stopBits, int parity) {//UartConn构造方法
    try {
        CommPortIdentifier commPortIdentifier = CommPortIdentifier.getPortIdentifier(commPort);//查找端口
        serialPort = (SerialPort)commPortIdentifier.open("Mrdu", 100);//打开串口
        outputStream = serialPort.getOutputStream();//获取输出流
        inputStream  = serialPort.getInputStream();//获取输入流
        serialPort.setSerialPortParams(baudrate, SerialPort.DATABITS_8, stopBits, parity);//1，波特率2，字节标准数据位长度3，字节的停止位数4，奇偶校验检查协议
    } catch (Exception ex) {
        logger.error(String.format("commPort: %s, baudrate: %d", commPort, baudrate), ex);
    }
}
//没有解析的数据添加到UartConnListener监听事件中
protected synchronized void fireDataAcquired(byte[] data) {
    for (UartConnListener listener : listeners) {
        listener.dataAcquired(this, data);
    }
}
//添加监听事件
public synchronized void addListener(UartConnListener listener) {
    listeners.add(listener);
}
//发送数据
public void sendData(byte[] pack) {
    if (serialPort != null) {
        try {
            logger.info("发送数据包操作  -->" + CommonUtil.printStr(pack));
            OutputStream output = serialPort.getOutputStream();//输出流
            output.write(pack);//写出pack数据
            output.flush();//更新
        } catch (IOException e) {
            logger.error("Send failed", e);
        }
    }
}

protected abstract void readCom();

}
为什么第一次连接成功了，第二次就不执行到这段代码。拔掉端口后丢失端口然后插上不执行此代码，无法接收数据

Answer 1

http://blog.csdn.net/danieluk/article/details/18518175