I installed rxtx this way:
  1. Copy rxtxParallel.dll to c:\Program Files\Java\jdk1.6.0_01\jre\bin\
  2. Copy rxtxSerial.dll to c:\Program Files\Java\jdk1.6.0_01\jre\bin\
  3. Copy RXTXcomm.jar to c:\Program Files\Java\jdk1.6.0_01\jre\lib\ext\

When I run this program
Java Code:
import gnu.io.*;

public class SimpleRead
	static void listPorts()
        java.util.Enumeration<CommPortIdentifier> portEnum = CommPortIdentifier.getPortIdentifiers();
        while ( portEnum.hasMoreElements() ) 
            CommPortIdentifier portIdentifier = portEnum.nextElement();
            System.out.println(portIdentifier.getName()  +  " - " +  getPortTypeName(portIdentifier.getPortType()) );
    static String getPortTypeName ( int portType )
        switch ( portType )
            case CommPortIdentifier.PORT_I2C:
                return "I2C";
            case CommPortIdentifier.PORT_PARALLEL:
                return "Parallel";
            case CommPortIdentifier.PORT_RAW:
                return "Raw";
            case CommPortIdentifier.PORT_RS485:
                return "RS485";
            case CommPortIdentifier.PORT_SERIAL:
                return "Serial";
                return "unknown type";
    public static void main(String[] args) 
I get following error
Java Code:
Exception in thread "main" java.lang.NoClassDefFoundError: gnu/io/CommPortIdenti
        at SimpleRead.listPorts(SimpleRead.java:7)
        at SimpleRead.main(SimpleRead.java:36)
Caused by: java.lang.ClassNotFoundException: gnu.io.CommPortIdentifier
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 2 more
Please help!