Java串口编程
前沿，要进行串口编程必须安装sun公司的comm包和相应的dll文件，若是用eclipse编程的话，把jar和dll文件复制到你所建的项目下，然后在eclipse中选择“项目"菜单,把项目下的.jar文件作为外部jars加入。
首先介绍两个类
CommPortIdentifier------串口和并口的硬件初始化类，同时包括选择是并口还是串口，这在它的常用构造方法里很好的体现了：CommPortIdentifier.getPortIdentifier(commName)，commName形式为COM1字符串时表示为串口.
SerialPort------------串口类的软件初始化类,包括输入输出流、设置参数等等。名字随看起来像是串口，但是它的意思实际上是序列话，包括串口和并口的基本设置.常用构造方法SerialPort serialPort = (SerialPort) portId.open("CommBean", 1000)，第一个参数为应用程序名称，第二个为超时时间。
注意点：
一、这两个类创建的时候，第一个类CommPortIdentifier应该设置为static，不然的话，运行到第二次便会出错，原因是还在使用串口，不能创建新的串口程序了。
二、在SerialPort设置参数的时候，数据位一定要设置好，不然的话，会出现？，反过来如果出现了？在程序结果里就是你的数据位设置有误。
三、如果程序里出现了“口”方框一样的东西就是你在没有数据送来的时候读取数据，解决方法是，等待有数据时才读串口。
程序实例：
package four;
import gnu.io.*;
import java.io.*;
import java.util.*;
public class COM implements Runnable, SerialPortEventListener {
private static Thread readThread;// static,保证该线程唯一
private volatile boolean toRead = false;// volatile 保证不同线程得到的值一致
private static CommPortIdentifier portId;// 只设portId为static就可，下面的输入输出流由portId产生
private SerialPort serialPort;
private String commName = "COM2";
private int bPS = 9600;
private int dataBit = 7;//和C51通信必须设为7位，不然输出不对
private int stopBit = 1;
private int pariteyBit = 0;
private OutputStream out;
private InputStream in;
private String encoding = "gb2312";
public boolean initComm() {
boolean ok = false;
try {// 打开硬件资源,获取并口
portId = CommPortIdentifier.getPortIdentifier(commName);
} catch (NoSuchPortException e) {
System.out.println("Get portid err" + e.getMessage());
return ok;
}
try {// 打开软件资源，设置进程名称和超时时间
serialPort = (SerialPort) portId.open("CommBean", 1000);
} catch (PortInUseException e) {
System.out.println("Get serialport err " + e.getMessage());
return ok;
}
try {// 设置数据传输参数
serialPort.setSerialPortParams(bPS, dataBit, stopBit, pariteyBit); } catch (UnsupportedCommOperationException e) {
System.out.println("Set port params err " + e.getMessage()); return ok;
}
try {// 创建输入流
in = serialPort.getInputStream();
} catch (IOException e) {
System.out.println("Create instream err " + e.getMessage()); return ok;
}
try {// 创建输出流
out = serialPort.getOutputStream();
} catch (IOException e) {
System.out.println("Create outstream err " + e.getMessage()); return ok;
}
try {// 监听串口
serialPort.addEventListener(this);
} catch (TooManyListenersException e) {
System.out.println("SerialPort addEventListener err"
+ e.getMessage());
}
serialPort.notifyOnDataAvailable(true);
if (readThread == null) {
readThread = new Thread(this);// 初始化读串口线程,复制主进程readThread.start();
}
// System.out.println(commName+" init is ok");// 调试语句
ok = true;
return ok;
}
public void setName(String commname) {
commName = commname;
public void setBps(int bps) {
bPS = bps;
}
public void setDataBit(int datebit) {
dataBit = datebit;
}
public void setStopBit(int stopbit) {
stopBit = stopbit;
}
public void setParityBit(int paritybit) {
pariteyBit = paritybit;
}
public boolean hasInput(){
boolean yes=false;
if(toRead)
yes=true;
return yes;
}
//获取波特率
public int getbaud(){
return bPS;
}
public static String[] listPort() {
int i = 0;
String commList[] = new String[5];// 假定为五个串口CommPortIdentifier commPort = null;
Enumeration portList = null;
portList = CommPortIdentifier.getPortIdentifiers();
// iterate through the ports.
while (portList.hasMoreElements()) {
commPort = (CommPortIdentifier) portList.nextElement();
if (commPort.getPortType() == CommPortIdentifier.PORT_SERIAL) { commList[i] = commPort.getName();
System.out.print(commList[i] + " ");// 调试语句
i += 1;
}
System.out.println();// 调试语句
return commList;
}
public synchronized String readPort() {
byte[] buf = new byte[1];
String msg = null;
boolean go = false;
try {
go = in.available() > -1;
} catch (IOException e) {
System.out.println("Check inputstream available err "
+ e.getMessage());
return msg;
}
if (go && toRead) {
try {
in.read(buf);
} catch (IOException e) {
System.out.println("Start read port err " + e.getMessage());
return msg;
}
notifyAll();
toRead=false;//必不可少，读了后标志为false
try {// 把字节转换为字符串
msg = new String(buf, encoding);
} catch (UnsupportedEncodingException e) {
System.out.println("byte to string err " + e.getMessage());
return msg;
}
return msg;
}
return null;
}
public synchronized boolean writePort(String msg) { boolean ok = false;
try {
out.write(msg.getBytes(encoding));
out.flush();
} catch (Exception e) {
System.out.println("Write port err " + e.getMessage()); return ok;
notifyAll();
// System.out.println("Writting port");// 调试语句
ok = true;
return ok;
}
public boolean closePort() {
boolean ok = false;
if (out != null)
try {
out.flush();
} catch (IOException e) {
System.out.println("Outstream flush err " + e.getMessage());
return ok;
}
try {
in.close();
out.close();
} catch (Exception e) {
System.out.println("Close IO err " + e.getMessage());
return ok;
}
serialPort.close();
// System.out.println("Close port");// 调试语句
return ok;
}
public void serialEvent(SerialPortEvent e) {
switch (e.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:
{ // System.out.println("没数据传来");//调试语句
break;
}
case SerialPortEvent.DA TA_A V AILABLE:
// System.out.println("有数据传来");//调试语句
toRead = true;
}
}
public void run() {
while (true) {
try {// 释放CPU 1s钟，给其他线程
Thread.sleep(1000);
// System.out.println("监听串口，休息一秒钟");//调试语句} catch (InterruptedException e) {
System.out.println("Readthread sleep err " + e.getMessage()); }
}
}
public static void main(String[] args) {
COM.listPort();
COM c = new COM();
if (c.initComm())
while(true){
if(c.hasInput())
System.out.print(c.readPort());
//c.writePort("Write");
try {// 释放CPU 给读线程1/bps 的时间,以便数据准确
Thread.sleep(1/9600);
} catch (InterruptedException e) {
System.out.println("Readthread sleep err " + e.getMessage());
}
}
}
}