Rxtx開源包下載地址：http://mfizz.com/oss/rxtx-for-java
windows平臺使用方法：
1、把rxtxParallel.dll、rxtxSerial.dll拷貝到：C:\WINDOWS\system32下。
2、如果是在開發的時候(JDK),需要把RXTXcomm.jar拷貝到..\jre…\lib\ext下；將rxtxParallel.dll、rxtxSerial.dll 拷貝到..\jre…\bin下；如：D:\Program Files\java\jre1.8.0_111\lib\ext
3、java，需要匯入RXTXcomm.jar包

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.TooManyListenersException;

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;

public class SerialUtil implements SerialPortEventListener{

    public int timeout = 6; // 超時時間  
    public String port = "COM1"; // 埠名稱  
    public int dataBits = 8; // 資料位  
    public int
 
 stopBits = 1; // 停止位  
    public int parity = 0; // 奇偶校驗  
    public int rate = 38400; // 波特率  

    private SerialPort serialPort; 
    boolean isOpen = false; // 埠狀態：開啟或關閉

   // static byte[] openJoin12 = new byte[] { 0xFE, 0x03, 0x21, 0x30,  0xFF,  0xFC,
    //      0x12, 0x03 }; // 開啟 12S 允許加網指令
   // static byte[] makeNet = new byte[] { 0xFE, 0x00, 0x21, 0x31, 0x10}; // 終端串列埠傳送組網指令

    public SerialUtil() {
        listPortChoices();
        //getPortStatus();
        open();
        sendData("hi");
        sendData("");
        //getPortStatus();
        //close();
        //getPortStatus();
    }

    public void getPortStatus() {
        if(isOpen) {
            System.out.println("埠已開啟");
        } else {
            System.out.println("埠已關閉");
        }
    }

    // 讀取所有串列埠名字
    public void listPortChoices() {
        CommPortIdentifier portId;
        Enumeration en = CommPortIdentifier.getPortIdentifiers();
        while (en.hasMoreElements()) {
            portId = (CommPortIdentifier) en.nextElement();
            System.out.println("port: "+ portId.getName() + " : " + portId.getPortType());
//          if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) { // 只得到com串列埠
//              System.out.println(portId.getName());
//          }
        }
    }

    // 開啟串列埠
    public void open() {
        try {
            CommPortIdentifier portId = CommPortIdentifier.getPortIdentifier(port);
            serialPort = (SerialPort) portId.open("controller", timeout);  
            //inputStream = serialPort.getInputStream(); 
            serialPort.addEventListener(this);// 增加一個監聽
            serialPort.notifyOnDataAvailable(true);  
            serialPort.setSerialPortParams(rate, dataBits, stopBits, parity);  
            isOpen = true;
        } catch (NoSuchPortException e) { // 埠不存在
            e.printStackTrace();
        } catch (PortInUseException e) { // 埠已經被佔用
            e.printStackTrace();
        } catch (UnsupportedCommOperationException e) { // 埠操作命令不支援
            e.printStackTrace();
        } catch (TooManyListenersException e) { // 太多的監聽者
            e.printStackTrace();
        }  

    }

    // 關閉串列埠
    public void close() {
        if (isOpen) {  
            try {  
                serialPort.notifyOnDataAvailable(false);  
                serialPort.removeEventListener();  
                serialPort.close();  
                isOpen = false;  
            } catch (Exception e) {  
                e.printStackTrace();
            }
        }
    }

    // 向埠傳送資料
    public void sendData(String data) {
        if(isOpen) {  
            try {  
                OutputStream outputStream = serialPort.getOutputStream();  
                outputStream.write(data.getBytes());  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
    }

    @Override
    public void serialEvent(SerialPortEvent event) {
        switch (event.getEventType()) {  
        case SerialPortEvent.BI: // 10  
        case SerialPortEvent.OE: // 7  
        case SerialPortEvent.FE: // 9  
        case SerialPortEvent.PE: // 8  
        case SerialPortEvent.CD: // 6  
        case SerialPortEvent.CTS: // 3  
        case SerialPortEvent.DSR: // 4  
        case SerialPortEvent.RI: // 5  
        case SerialPortEvent.OUTPUT_BUFFER_EMPTY: // 2  
            break;  
        case SerialPortEvent.DATA_AVAILABLE: // 1  
            try {  
                // 多次讀取,將所有資料讀入  
                byte[] readBuffer = new byte[1000];  
                InputStream inputStream = serialPort.getInputStream();  
                while (inputStream.available() > 0) {  
                    inputStream.read(readBuffer);  
                }  
                System.out.println(new String(readBuffer));  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
            break;  
        }  
    }

    public static void main(String[] args) {
        SerialUtil su = new SerialUtil();
    }

}