这个简单的程序包括以下文件：

       imu.java (主程序)
       readbuffer.java (从缓冲区读取一个消息)
       readserial.java (读取串口数据并放入缓冲区)
       serialbuffer.java (缓冲区)
       writeserial.java (不断的往串口送星号'*')

测试程序：

       sendcom.java (将一个数据文件往串口发送)
       send.txt (供测试用的数据文件)

在这个通讯程序中使用了一个简单的协议，既不同的消息之间用星号'*'作为分隔。这个程序中的问题是readserial进程和writeserial进程不能够同时启动，出错信息是不能够打开串口，因为同样一个串口不能够同时被打开两次(在readserial中声明了filereader

测试程序：

       sendcom.java (将一个数据文件往串口发送)
       send.txt (供测试用的数据文件)

在这个通讯程序中使用了一个简单的协议，既不同的消息之间用星号'*'作为分隔。这个程序中的问题是readserial进程和writeserial进程不能够同时启动，出错信息是不能够打开串口，因为同样一个串口不能够同时被打开两次(在readserial中声明了filereader和在writeserial中声明了filewriter)。这样是不能够实现全双工通讯的。不知道有没有做过的大侠能够讲讲处理的办法。

/*
*
* imu.java 1.0
* main program for serial communication
*
* created: march 27, 2001
*
* author : qingye jiang (john)
* american gnc corporation
* 888 easy st, simi valley ca 93065-1812
*
* contact: (805) 582-0582 (tel), (805) 582-0098 (fax)
* qjiang@tsinghua.edu
*
*/

import java.io.*;

class imu
{
       public static void main(string[] args)
       {
               //to do: add your java codes here

               file comport = new file("com1");

       serialbuffer sb = new serialbuffer();
       readserial r1 = new readserial(sb, comport);
       readbuffer r2 = new readbuffer(sb);
       writeserial r3 = new writeserial(comport);

       r1.start();
       r2.start();
       r3.start();
   }
}

/*
*
* readbuffer.java 1.0
* program to read the serial buffer
*
* created: march 27, 2001
*
* author : qingye jiang (john)
* american gnc corporation
* 888 easy st, simi valley ca 93065-1812
*
* contact: (805) 582-0582 (tel), (805) 582-0098 (fax)
* qjiang@tsinghua.edu

*
*/

import java.io.*;

public class readbuffer extends thread
{
   private serialbuffer combuffer;

   public readbuffer(serialbuffer sb)
   {
       combuffer = sb;
   }

   public void run()
   {
               string msg;

       while (true)
       {
               msg = combuffer.getmsg();
               system.out.println(msg);
       }

   }
}

/*
*
* readserial.java 1.0
* program to read characters from the serial port and put it
* to the buffer
*
* created: march 27, 2001
*
* author : qingye jiang (john)
* american gnc corporation
* 888 easy st, simi valley ca 93065-1812
*
* contact: (805) 582-0582 (tel), (805) 582-0098 (fax)
*       qjiang@tsinghua.edu
*
*/

import java.io.*;

public class readserial extends thread
{
   private serialbuffer combuffer;
   private file comport;

   public readserial(serialbuffer sb, file port)
   {
       combuffer = sb;
       comport = port;
   }

   public void run()
   {
               int c;
               try
               {
                       filereader in = new filereader(comport);
               while (true)
           {
               c = in.read();
               combuffer.putchar(c);
           }
               try
               {
                       filereader in = new filereader(comport);
               while (true)
           {
               c = in.read();

               combuffer.putchar(c);
           }
       } catch (ioexception e) {}
   }
}


/*
*
* serialbuffer.java 1.0
* class that implements the serial buffer
*
* created: march 27, 2001
*
* author : qingye jiang (john)
*   american gnc corporation
* 888 easy st, simi valley ca 93065-1812
*
* contact: (805) 582-0582 (tel), (805) 582-0098 (fax)
* qjiang@tsinghua.edu

*
*/

public class serialbuffer
{
   private string content = "";
   private string currentmsg, tempcontent;
   private boolean available = false;

   public synchronized string getmsg()
   {
       int sepmark;

       if ((sepmark = content.indexof('*')) == -1)

{
               available = false;
               while (available == false)
               {
               try
               {
                   wait();
               } catch (interruptedexception e) { }
               }
               sepmark = content.indexof('*');
       }

       currentmsg = content.substring(0, sepmark);
       tempcontent = content.substring(sepmark+1);
       content = tempcontent;
       notifyall();
       return currentmsg;
   }

   public synchronized void putchar(int c)
   {
       character d = new character((char) c);
       content = content.concat(d.tostring());
       if (c == '*')
       {
               available = true;
       }
       notifyall();
   }
}


/*
*
* writeserial.java 1.0
* program to send a character to the serial port
*
* created: march 27, 2001
*
* author : qingye jiang (john)
* american gnc corporation
* 888 easy st, simi valley ca 93065-1812
*
* contact: (805) 582-0582 (tel), (805) 582-0098 (fax)
* qjiang@tsinghua.edu
*
*/

import java.io.*;

public class writeserial extends thread
{
   private serialbuffer combuffer;
   private file comport;

   public writeserial(file port)
   {
       comport = port;
   }

   public void run()
   {
               int c;
               try
               {
                       filewriter out = new filewriter(comport);
               while (true)
           {
               out.write('*');
           }
       } catch (ioexception e)
       {
               system.out.println(e.getmessage());
       }
   }
}
/*
*
* sendcom.java 1.0
*
* project: java based information exchange support system
* onboard plug-in system
* sending data through serial port
*
* created: march 15, 2001
*
* author : qingye jiang (john)
* american gnc corporation
* 888 easy st, simi valley ca 93065-1812
*
* contact: (805) 582-0582 (tel), (805) 582-0098 (fax)
*
*/

import java.io.*;

public class sendcom
{
   public static void main(string[] args)
   {

               file outfile = new file("send.txt");
               file comport = new file("com2");

               int c;

               try
               {
                       filereader in = new filereader(outfile);
                       filewriter out = new filewriter(comport);
                       while ((c = in.read()) != -1)
                               out.write(c);
                       in.close();
                       out.close();
               } catch (ioexception e) {}

       }
}

send.txt*

this is a sample of the data file for program testing. *

it should be in the same directory as the sendcom.class file.*

when you run this sample program, connect your com1 and com2 with a
serial cable so that you can test this program on one machine. if
you have two machines, you can connect the two machine via a serial
cable and test it. modified the definition of comport in the program
if necessary. *

thank you for testing this program. if you have any suggestions please
kindly let me know. *